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The spectra of cadmium Giovando, Laurence Frank 1948

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THE SPECTRA OF CADMIUM by LAURENCE  FRANK  GIOVANDO  A Thesis submitted i n P a r t i a l Fulfilment of the Requirements f o r the Degree of  MASTER  OF ARTS  i n the Department of PHYSICS  9-1 SITY OF BRITISH COLUMBIA OCTOBER,  194&  ABSTRACT  In order to f a c i l i t a t e a l a t e r determination (which, i n c i d e n t a l l y , w i l l involve the study of hyperfine structure) of various nuclear properties o f Cadmium, a preliminary survey, both experimental and t h e o r e t i c a l , has been undertaken o f the gross spectral structure o f that element. A l i g h t source, consisting of an electrodeless discharge i n which the excitation o f the various spectra could be varied i n some degree, was constructed and conditioned.  The i l l u m i n a -  t i o n from t h i s source was then photographed with the a i d o f a Hilger E I Quartz Spectrograph; regions 68O0X  - 330o£, 3300A  exposures were taken of the  - 25O0A, and 2500A - 200oL  The  positions o f the spectral l i n e s appearing on the plates were measured with t h e a i d o f a H i l g e r comparator, and the wavelengths were then calculated by means o f the Standard Hartmann dispersion formula.  About 150 Cadmiumlines which had already  been l i s t e d by previous workers were i d e n t i f i e d ;  21 other  l i n e s - apparently new ones, since t o the writer's knowledge they have not as yet been mentioned i n the l i t e r a t u r e - also were found.  These l a t t e r l i n e s were concentrated i n the region  60001 - 3900X. Theory reveals that.the hyperfine structure o f Cadmium II should be o f greater value i n the above-mentioned determinat i o n than that.of the a r c spectrum.  Therefore a study of an  i s o e l e c t r o n i c sequence Involving Cadmium I I was c a r r i e d out with an eye t o increasing the knowledge of t h i s f i r s t spark spectrum's term structure.  The v a l i d i t y o f the various o p t i c a l  doublet laws has been tested f o r such an exemplary i s o e l e c t r o n i c sequence.  ACKNOWLEDGMENTS  The author wishes t o express h i s h e a r t f e l t appreciation t o Dy.A.M.Crooker, o f the U n i v e r s i t y of B r i t i s h Columbia, f o r the expert help and advice given him during the conduct o f the present research.  He wishes also t o acknowledge h i s indebtedness to the National Research Council o f Canada, under whose grant the work has been carried out.  TABLE OF CONTENTS  Page 1 II  Introduction:  Object o f Research  1  Summary o f Previous Work A. The Spectra o f Cadmium  3  B. The Hyperfine Structure o f Cadmium  4  I I I Theory A. Fine-Structure o f "Spectfcal Lines B. Hyperfine Structure o f Spectral Lines C. l8oelectronic Sequences IV  Experimental A. B. C. D.  V  The Electrodeless Discharge The Spectrograph Operation o f the Source Exposure and Measurement o f Plates  32 34 36 37  Results A. Results of Wave-length Measurements B. Investigations of Isoelectronic Sequences  VI  7 17 25  Bibliography  40 41  PLATES  I II  The ELectrodeless Discharge:  the Source C i r c u i t  General View o f Apparatus Q  III IV V VI  VII  VIII  IX  X  XI  Detailed View of Source Cadmium Spectrum : Region  6800A  Dispersion Curve f o r H i l g e r EI Moseley Diagram:  -  3300S  Quartz Spectrograph  F i r s t Form of the I r r e g u l a r Doublet Law  Second Form o f the Irregular-Doublet Law  Regular Doublets:  The Lande Doublet Formula  Energy Level Diagram o f Ag-like I s o e l e c t r o n i c  Sequence  Modified Moseley Diagram of Ag-like Isoelectronic Sequence  Energy Level Diagram of Cadmium I  THE SPECTRA OF CADMIUM I  INTRODUCTION  U t i l i z a t i o n of r e s u l t s obtained from researches i n spectroscopy has been instrumental i n the- formulation of the atomic theory of matter, and indeed has contributed much to our knowledge o f the atom i t s e l f *  Through the study o f the so-called s p e c t r a l  f i n e - s t r u c t u r e , science has learned a multitude of f a c t s about the outer part o f the atom, i . e . about the arrangements and motions of the planetary electrons.  This information has i n t u r n been  invaluable f o r an understanding  o f the p e r i o d i c table*  Such a contribution however, great as i t i s , has by no means exhausted the usefulness o f spectroscopic work.  Given  more modern equipment, possessing such advantages as very great resolving power and dispersion, the spectroscopist has i n many cases been able to resolve the f i n e - s t r u c t u r e i n t o even more d e l i c a t e hyperfine patterns.  This new discovery has lead t o an  increase i n the knowledge (which i s s t i l l f a r from complete) o f the main constituent o f the atom, the nucleus; because, to account f o r the various rules pertaining to the formation o f hyperfine structure, and f o r the exceptions to these r u l e s , theoreticians have been lead t o postulate such nuclear properties as a mechanical moment, a magnetic moment, and even an e l e c t r i c quadrupole e f f e c t . Since the advantages o f the r e l a t i v e l y e a s i l y excited hyperfine spectra u s u a l l y f a r outweigh such disadvantages as pattern  complexity and smallness of component separation, spectral analysis has accounted for the major part of the information presentlyavailable about such nuclear properties* A firm basis f o r the story of those hyperfine states best suited for the determination of nuclear characteristics demands a sound knowledge of the spectral gross structure of the element concerned. I t i s to s a t i s f y such a need that the following study, both experimental and theoretical, of the pertinent element (Cadmium) has been undertaken.  -3II.  A.  SUMMARY OF PREVIOUS WORK  THE SPECTRA OF CADMIUM. The f i r s t exhaustive c l a s s i f i c a t i o n o f wave-lengths  i n the arc spectrum o f Cadmium was made by Paschen 1 have since been supplemented by those o f Fowler  2  His r e s u l t s  and Ruark^.  The most important analysBS o f the v i s i b l e and near-  - violet ultra,regions o f the f i r s t spark spectrum Salis^-, Takahashi-*, and Lang°.  have been made by von  The extreme u l t r a - v i o l e t  lines  have been studied by the brothers Bioch?. E a r l i e r work on the spectrum o f Cadmium I I I consisted mainly o f the c l a s s i f i c a t i o n o f several m u l t i p l e t s by Gibbs and White**, and, independently, by McLennan, McLay and Crawford.9.  1  Paschen, F., Ann.d.Phys., 30, 746 : 1909. Paschen, F., Ann.d.Phys., 21 8°° : 1911.  2 Fowler, A., Report on Series i n Line Spectra, Fleetway Press, 1922. 3  Ruark, A.E., Jour.Opt.Soc.Am., 11, 199: 1925.  4  von S a i l s , G., Ann.d.Phys., 7J>, 145: 1925.  5  Takahashi, I . , Ann.d.Phys.,  6  Lang, R.J., Proc.Nat.Acad.Sci., 1 £ , 414:  7  Bioch, L.and E., Ann.dePhys., £, 325: 1936.  8  Gibbs, E.G., and H.E.White, Phys .Rev., 31, 776: 1928.  42: 1929. 1929.  9 McLennan, J.C., A.B.McLay, and M.F.Crawford, Trans. Roy.Soc.Can., 22, 45:1928.  Recent research on the extreme-ultra v i o l e t has been conducted by Mazumder'-O. Wave-lengths i n the Cadmium IV spectrum  have been  given by Esclangan^" and by the l a t e r work o f Green-^. Theoretical calculations, resulting i n formulae f o r doublet and t r i p l e t separations, screening constants, quantum defects, and the l i k e , have been made largely by Fues*3, Lancufe^, Turner ^, S i g i u r a , Unsold 3  16  17  and Badami . ld  B. The Hyperfine Structure of Cadnriiunu The very considerable work done on the hyperfine structure of Cadmium i s highlighted by the early paper of Schuler  10  Mazumder, K.C, Ind.Jour.Phys., 17_, 229: 1943.  11  Esclangan, F., Jour.de Phys.et radium, 2, 52: 1926.  12  Green, M., Phys. Rev., 60, 117:  13  Fues, E., Arm.d.Phys., 6£, 1: 1920.  14  Landa, A., Zeits. f.Phys., 2£, 46:  15  Turner, L.A., P h i l . Mag., 4J*, 384:  16  Sigiura, Y., Jap.Jour.Phys., 3_, 155:  17  Unsold, A., Zeits. f.Phys., 3J>, 92:  18  Bad ami, E., Proc.Phys.Soc, 4jb 538:  1941.  1924. 1924. 1924. 1926. 1931.  and Brack ?. 1  These investigators found, by a study of the t r i p l e t  a r i s i n g from the t r a n s i t i o n isotopes - H I  2 3p^ ^ ^, that the two  2 3s±—*  and 113 - possess a nuclear "spin" I o f 1/2,  odd  while  the four even isotopes - 110, 112, 114, 116 - have I = 0. Isotope displacement Schuler and Westmeyer20.  i n Cadmium I I has been studied by  Jones  21  has shown that 12 out of 13 l i n e s  o f Cadmium I I he examined possessed no structure; the t h i r t e e n t h ,  2 however, revealed the ground term,  S, as double, which f a c t y i e l d e d  an average value of -^63 nuclear magnetons f o r the magnetic moment  u  x  of the odd isotopes of Cadmium. The hyperfine structure has also been studied by A l b r i g h t , while abnormal i n t e n s i t i e s i n the structure have been 2 2  examined by Schuler and Keyston 3. 2  Apparently there-has not as yet been discovered, i n the hyperfine structure o f Cadmium^ that type of deviation from the i n t e r v a l r u l e which would lead ore to postulate the existence of a nuclear e l e c t r i c quadrupole moment*  19  Schuler, H., and H.Bruck, Zeits.< f .Phys.,56,291:  20  Schuler, H., and H.Westmeyer, Zeits., f.Phys., &,  21  Jones, E.G.,  22  A l b r i g h t , C.L.,  23  Schuler, H., and J.E.Keyston, Zeits.;f.phys., 7JL, 413:  Proc.Phys.Soc, 4J>, 625: Phys. Rev.,  26,  847:  1929. 685:1933.  1933. 1930. 1931.  -6-  Attention i s here drawn- to a very complete bibliography, that of R . C . G i b b s ^ , which thorotighly covers the e a r l i e r work (of the period 1920-31) i n the f i e l d s summarized i n the above sections.  24  Gibbs, R . C . , Rev.Mod.Phys., 4^ 278:  1932.  -7III  A.  THEORY  Fine-Structure of Spectral  Lines,  In t h e i r c l a s s i f i c a t i o n s of simple spectra,  early  workers r e l i e d almost wholly upon the discovery of series of lines.  Such series were found t o have the same general  appearance as the series of hydrogen;  the l i n e s both became  l e s s intense on, and converged to l i m i t s on, the short wavelength side o f the spectrum.  Any  series of hydrogen can  be  found by means of the formula  ~*  (1)  ~n*  where Tg i s the wave-number of the p a r t i c u l a r series l i m i t . I t was  shown soon afterwards that t h i s formula might be  generalized  f o r series of other "hydrogen-like" atoms by  the  expression  ^  TT+a)  (2)  2  where a i s a constant c h a r a c t e r i s t i c of the relevant and M runs through a sequence o f i n t e g r a l values.  series  In both the  above formulae, R represents the so-called Rydberg constant. These r e s u l t s , empirical i n nature, showed conclusively  that  spectral l i n e s must be produced by r a d i a t i v e t r a n s i t i o n s between stationary states o f an atom.  -8-  The f i r s t successful attempts t o explain the existence  25  of the above series were made by Bohr and Sommerfeld  26  , who  applied the e a r l i e r quantum theory to the hydrogen and hydrogenl i k e atoms.  The work involved the hypothesis, which was found  to be correct t o a f i r s t approximation, that the total-energy levels of an atom can be completely described by the valence elsctron^'s o r b i t a l angular momentum. In the l a t e r stages of the work, t h i s momentum was "quantized" to possess only integral multiples of h, i.e., kfi, with k i n t e g r a l .  (Subsequent theoretical  developments have made i t desirable to replace k by 1?, where  it s k - 1).  Possible transitions between the energy levels were  found to be given by the selection rule A k  =  +1.  The above mentioned theory does not, however, account for the well-known fact that many of the l i n e s resulting from such transitions are found i n r e a l i t y to consist of two or more components.  To account generally f o r t h i s so-called "fine-  structure", Goudsmit and Uhlenbeck ' suggested that each electron 2,  ,  i n the atom be supposed to spin, and thus t o possess a spin angular momentum) given i n magnitude by ^ n.  Now, since a  25 Bohr, N., Phil.Mag., 26, 1, 476, 857: 1913. 26 Sommerfeld, A., Ann. d.Phys., %L, 1: 1916. 27 £ L  Uhlenbeck, G.E., and S.A.Goudsmit,  953: 1925.  Naturwissenschaften,  -9spinning e l e c t r i c charge gives r i s e t o a magnetic f i e l d , and since an o r b i t a l motion o f a charge i s equivalent t o a current with a r e s u l t i n g magnetic f i e l d , the spin and o r b i t a l angular momenta w i l l combine because of the i n t e r a c t i o n of these two fields. Consider f i r s t the general case o f an atom containing several valence electrons.  (The spin  moment a o f each electron  can be combined v e c t o r i a l l y to form a resultant spin moment S. A s i m i l a r combination o f the o r b i t a l angular momenta, each by JL, gives L.  denoted  The resultant angular momentum as a whole i s then  i n t u r n given v e c t o r i a l l y by  L + S and i s represented by J .  (The type o f electronic i n t e r a c t i o n permitting such i s termed L - S, o r Russell-Saunders, coupling). 8 2  combinations To b r i n g the  r e s u l t s o f such a v e c t o r i a l treatment i n t o accord with those o f the more recent, i . e . quantum-mechanical, calculations, the magnitudes o f the vectors Jt  (L + I ) f i , and  3 , L and S are given by VtP(J + 1) H,  Js (S  1) fi r e s p e c t i v e l y .  The values that'  L can assume are i n t e g r a l , and those o f S are i n t e g r a l , h a l f i n t e g r a l or zero.  The values o f J , which are i n t e g r a l or h a l f -  i n t e g r a l , are determined by the quantum-mechanical condition  28 R u s s e l l , H.N., and F.A.Saunders, 61, 38: 1925.  Astrophys. Jour.,  -10-  |(L + S)| >  J  > |(L  -  (3)  S)J  where the intermediate quantities - between the terminal ones shown -  d i f f e r by unity.  values for J i f L<S,  (Thus there exists 2L + 1 possible  and 2S+1  possible ones i f L > Sj  Each  J, being the result of a different orientation of the quantum vectors L and S, corresponds to a different energy state of the atom i n question,  when the concept of electron spin i s  considered, therefore, i t i s found that transitions between l e v e l s characterized by different J (and L) give r i s e to the ordinary fine-structure multiplets.  The two selections rules  which determine such transitions are given by: A L and  AJ  m  ± 1 or 0, with the additional r e s t r i c t i o n s that  the transitions L • 0 — • forbidden.  - i 1 or 0,  La  0  and J  a  0 —*  J  -  0  be  I t i s to be noted that, f o r the case of a single  valence electron, the nomenclature J , L and S becomes j , £ and s respectively. but two values) JL +  For each value of and  £ - \  t  j can possess  corresponding respectively  to the electron spin p a r a l l e l or a n t i - p a r a l l e l to the o r b i t a l angular momentum. Here then i s the explanation of the doublet levels of the alkali-type atoms'. Not only the r e l a t i v e wave-lengths, but also the relative i n t e n s i t i e s of the fine-structure components may deduced from the L and S (or H and s) values of the levels concerned. A very useful qualitative rule, established on the basis of the older quantum theory, was given by  be  Sommerfeld and  Heisenberg29«  the t r a n s i t i o n s where A J .  The strongest l i n e s are due t o A L ; weaker l i n e s - s a t e l l i t e s  of the f i r s t order - a r i s e when  AJ  S  A L  ±  1; and the  weakest l i n e s - s a t e l l i t e s o f the second order A L ~ 2.  AJ m  occur when  Quantum-mechanical v e r i f i c a t i o n and  30 elaboration o f such r u l e s have been given by Dirac  .  A few of the more important quantitative r e s u l t s w i l l next be given.  F i r s t t o be dealt with w i l l be the  doublet separations i n a l k a l i - l i k e atoms.  The i n t e r a c t i o n  energy, i . e . the energy change-of a fine structure l e v e l characterized by the quantum "magnetic  11  numbers n and £ - due t o the  property of the electron has been calculated by  Pauli31, Gordon^ , Dirac33, D a r w i n ^ and others. 2  The r e s u l t s  of the calculations give the term s h i f t corresponding t o t h i s energy as At m  -Rd  j?2  2  •a? Jttt+1) •(<+!)  -I2 _  (  2  CM:  >  29  Sommerfeld, A., and W.Heisenberg, Z e i t s .  30  Dirac, P.A.M., Proc.Roy.Soc, A 111, 281: 1926.  31  P a u l i , W., Z e i t s .  32  Gordon, W., Z e i t s ,  33  Dirac, P.A.M., Proc .Roy. S o c , A 117.  34  Darwin, C.G., Proc .Roy . S o c , A Ll6, 227:  n , 131: 1922.  f.Phys., f . Phys. 4J*,  ct.Phys.  601: 1927. 11: 1929. 610: 1927. 1927.  1  (4)  -12and ~8 have,of course, the  where the quantum vectors j ,  Jl(3+-±)  magnitudes  respectively,  Jl(t +•  -fi,  1)11, and  JB(S + 1)  <*• i s the "Sommerfeld fine-structnre constant}  1  given by ZCEe ch  2  ~  1 137.3  (5)  (4) i s o f t e n written as AT  ^ a . Cf 2 2  -  -  I  _ -s2  2  ) c w r  ,  ( 6 )  where: a(the f i n e - s t r u c t u r e i n t e r a c t i o n constant) = Rot  2  ^  cmT  (7)  1  I t i s t o be noted that f o r s electrons, having J. s 0 and thus j e ^,  AT  s 0; therefore a l l s states should be s i n g l e , a f a c t  which has been amply confirmed by For any doublet j •  A  J a  - \ f o r the lower l e v e l .  experiment.  JL +- § f o r the upper l e v e l and By substitution of these  values i n (4) one sees a f t e r some mathematical  manipulation  that the numerical value o f the doublet separations f o r a l k a l i - l i k e atoms i s given by:  a  Rri  2  cm-.  n3 J£ ( JC v- 1) Equation (8) may be modified to read  1 s  5.82  Z^ 1  cm"!  n3 Ji <J.+\)  (8)  AV  -  ( Z -  Rdg  8  )4  cmT  1  where s i s a "screening constant" which indicates the shielding of the nucleus by the one or more closed electron sub-shells. Equations (8)  and (9) hold good f o r the case of the non-  penetrating o r b i t s of the valence electron, i . e . those o r b i t s f o r which the observed energies are almost equal to those o f the corresponding hydrogen-like o r b i t s . In the event of penetrating o r b i t s , which by d e f i n i t i o n have term values d i f f e r i n g appreciably from those of the corresponding hydrogen-like o r b i t s , s t i l l another m o d i f i c a t i o n of (8) must be employed.  Landed, upon the basis of the o l d e r  quantum theory, and before the introduction of the concept of electron spin, showed that i n t h i s case the doublet separation i s given by  A\j -  Rd£  £  ^  2  o  £  n*3  cm-1  2  <* ( i  + D  ( )  ^  10  The e l e c t r o n i c o r b i t was considered as being divided i n t o two parts, an inner one, i n which the electron was subject to the a t t r a c t i o n of the charge charge was  35  Z„  .  £  Q  Z  L  , and an outer where the a t t r a c t i n g  w i l l here be equal t o unity f o r a  Lands, A., Z e i t s .  ,f.Phys., 2j>,  46:  1924  -14neutral atom, 2 f o r a s i n g l y ionized atom, and so f o r t h .  With  the introduction o f appropriate screening constants s^ and s , Q  (10) becomes: =  R«*  (% -  2  n * =  n - u  2  2(1  n*3 Here  s„)  ( g  -  S l  )2  cm?!  + 1)  (with u the so-called "quantum defect") i s  the " e f f e c t i v e quantum number" defined by  T R  s j? — > * 2 n **  modification o f the hydrogen-like term value formula. (9),  a  Equations  (10) and (11) are of value i n the treatment of i s o e l e c t r o n i c  sequences, and w i l l be mentioned further under that heading of theory. Next w i l l be given a few quantitative r e s u l t s f a r the t r i p l e t s occurring i n the spectra o f atoms with two electrons.  The following conclusions, which are discussed very  f u l l y by Pauling and Goudsmit of  valence  L - S coupling.  are based upon the v a l i d i t y  I f but one of the electrons i s i n an s o r b i t ,  the i n t e r a c t i o n energy due t o electron spin produces a term s h i f t given by 4»  -  -a  1 ; >  l  J  2  -  (rv>n-s^  L  2  2  ) a*  42  (  )  1  2  )  where: *L.-=  +**  2  -  * i )  4  c m  "  1  (33)  36 Pauling, L., and S.A.Goudsmit, The Structure o f Line Spectra, McGraw-Hill, 1930,  -15The above (with  a screening constant) holds f o r non-penetrating  o r b i t s ; f o r a penetrating S o r b i t (13) becomes, o f course, Ro Z  ?  2  n^  2  Z:  cm"  2  1  (U)  i t f ^ 1) Of,/'*) 2  For n e i t h e r electron an s - electron, the term displacement i s expressed by AT  = -(EL. -f- a ) f l - L 2  - S ) cm?'  2  (15)  2  i n which a^, equalling 2  I*  Bo^Z^) .6 (s^l)i-S(S^l)-8 (8 -^l)J (i ^l>L(l^l)^(^l) 2  1  BltjUi+U  2  1  .04*1) • 2S(S-»-l)  cmT  1  1  • 2L(L+1) (16)  and a , given by (16) with subscripts 1 and 2 interchanged,are the 2  i n t e r a c t i o n constants o f the two electrons. The t o t a l t r i p l e t separation f o r the case o f one selectron i s  AvZ  Roc (Z - S j ) ^ cm?  1^(4  (17)  1  f 1)  and i s found by s u b s t i t u t i o n o f the maximum and minimum values (of J ) ,JL]_-P-"L and  - 1  respectively, i n (12).  I t i s to be  noted that (17) i s i d e n t i c a l i n form with ( 9 ) , the equation f o r the a l k a l i doublet separation. For two l i k e electrons, t h e t o t a l t r i p l e t width i s , from (15), given by 2 - 1 AVZ Roc (Z - \ ) (L + j )  cmT  (18)  ••16" One of the simplest methods o f determining whether the electron coupling i s of the L -"S, or Russell-Saunders, type i s to t e s t f o r the presence of the so-called i n t e r v a l r u l e , ,37 discovered by Lande.  This r u l e states that f o r any t r i p l e t , or  f o r any multiplet of a higher order, the separation o f two terms, associated with quantum numbers J and J - 1  adjacent  respectively,  i s proportional to J , i . e . to the l a r g e r J value.  For the energy  of any multiplet term may be expressed by \ •Where T  G  +  | £ J( J + 1) - L(L + 1) - S(S +-1)  ^  i s the hypothetical value of the doublet centroid.  The separation of two m u l t i p l e t components characterized by J and J - 1  values  i s therefore |  £ J ( J *• 1) - ( J - 1)  AJ  5  (19)  which i s j u s t Lande*s empirical r e s u l t . In the following table are compared observed and t h e o r e t i c a l i n t e r v a l r a t i o s f o r various t r i p l e t s o f the Cadmium I spectrum: Configuration  3pg - 3j»o  5S5P  1171.1  5s5d  -  5s6d  -  37  o n ^p03 o ° p  541.9  _ 3  „ -?n  D  .  .  -  Observed Interval . Ratio  J+1 J  -  -  2.16  2  -  18.2  11.7  1.55  1.5  -  8.2  5.8  1.41  1.5  Lande, A., Z e i t s . ;f.Phys., 15.,  189:  1923.  -17I t should be mentioned i n conclusion that  L-S  coupling, upon whose v a l i d i t y the r e s u l t s o f the foregoing treatment of f i n e - s t r u c t u r e are based, holds s t r i c t l y only i n the case of the l i g h t e r elements, i . e . those with small nuclear charge.  Here the e l e c t r o s t a t i c i n t e r a c t i o n between the  d i f f e r e n t extra-nuclear electrons i s much greater than the various spin-orbit i n t e r a c t i o n s . However, i n the heavier elements, the l a t t e r i n t e r a c t i o n s tend to predominate; such a tendency gives r i s e t o the so-called " j - j coupling", i n which the  3**8  of each  i n d i v i d u a l electron are strongly coupled together to form the resultant J .  Most s p e c t r a l l i n e s and energy l e v e l s can be  c l a s s i f i e d by means of e i t h e r coupling scheme, or by some intermediate modification o f these schemes. B.  Hyperfine Structure o f Spectral L i n e s . Instruments of high-resolving power, such as  Michelson  interferometers, revealed i n many s p e c t r a l l i n e s a complex structure with component i n t e r v a l s ranging from about 0.1 about 1.0  cm"  1  i n magnitude.  to  The smallness o f the i n t e r v a l s  i t s e l f suggested that the so-called "hyperfine-structure" could hardly be a t t r i b u t e d to the electron spin which helps to explain completely ordinary fine-structure.  Thus i t seemed necessary  either to postulate some further fundamental property of the electron besides i t s mass, charge and spin, or, more acceptably, to ascribe the phenomenon to the  nucleus.  -18Two means have been proposed by which the nucleus could be responsible f o r the hyperfine e f f e c t .  The f i r s t concerns  the existence o f isotopes and gives r i s e t o the so-called "isotope e f f e c t " .  The second, and more important, postulates the  existence o f a nuclear magnetic moment.  The l a t t e r theory only  w i l l be considered here* The hypothesis was f i r s t put forward by P a u l i ^ . I t assigned to t h e nucleus an angular momentum I equal t o ( i n the form agreeing with quantum-mechanical r e s u l t s ) Jl ( I +-1) n . With t h i s angular momentum was t o be associated a magnetic moment; i t was presumed that, when the f i e l d o f the nuclear magnetic dipole acted upon the valence electron - ( S ) , a s p l i t t i n g o f the f i n e structure electronic term occurred.  I , and the r e s u l t a n t electronic  angular momentum given, as before, by J , were assumed to combine forming a resultant atomic moment F -  J F (F +-1) i i .  Experience  with similar l i n k i n g of L and S suggested that p o s s i b l y the s e l e c t i o n  F • rules AF > case.  0 - *  ± 1 or 0 (with F • 0 forbidden)  might hold i n t h i s  S i m i l a r l y one would expect 2 1 + 1 hyperfine l e v e l s f o r 1< J  and 2J -+-1  levels for J ^ I .  Analogous  to the case o f ordinary  f i n e - s t r u c t u r e , however, the v a l i d i t y of such r u l e s and o f the Lande i n t e r v a l r u l e i n hyperfine structure would demand that the i n t e r a c t i o n energy between the nuclear magnetic d i p o l e and the valence electrons be proportional to the cosine o f the angle  38  P a u l i , W., Naturwissenschaften,  12, 741: 1924.  -19* -*•  ->  between the quantum vectors I and J* I t has been shown  by  Fermi^?, B r e i t ^ , Goudsmit^", and others that - i n the case of a single valence electron - the term s h i f t corresponding to the interaction energy i s indeed given by: -v ->. „ cm-1 Als a ( I •j ) t  S  |  + 1)  £F(F  - -1(1+1)  - j(  j  cm-1  (20)  where: a(the interaction constant) s Rd? 3  a  g(I)  cm"*l  (21)  U * i ) j ( J + 1) 1838  for a non-penetrating o r b i t , and a =  Rd  £  2  n*  £  U+i)  3  o  cm  ~*  1838  j  (22)  for a penetrating o r b i t . The so-called "nuclear g-factor (g(l)) i s the r a t i o of M  the nuclear magnetic and mechanical moments, and i s defined by the equation: tf  T 1  "  gC ) 1  J L J 2 Me  I U + l) &  (23)  where M i s the proton mass. 39  Fermi, £., Zeits. f . Phys., 60,  40  Breit, G., Phys.Rev., 3J,  41  Goudsmit, S.A.,  Phys. Rev.,  51: 3J>  320:  1930.  1931. 663:  1931.  -20By substitution i n (22) of the Lande alkali-doublet formula given previously by (10)^ one obtains the r e l a t i o n : a - g ( l ) AV {£ 1838 Z  +  U+1t)  cmS  1)2  (24)  i (J^D  B r e i t ^ and Racah^ have pointed  out that «. r e l a t i v i s t i c  2  correction must be made i n the theory, especially for the case of the heavier elements. The correction can be given by multiplying (19) b y K  where:  K . 4.1 (4p and  2  ,p  2  = (J + if  - ( ^ )  (25)  2  - DP  \s  | U+-D - ( o c i i ) j - i - ^ - ( ^ ) j 2  2  8  2  2  (26)  For the special case of an s valence electron, where equation (24) theoretically should not hold, a satisfactory modification has been given by Goudsmit, namely that a - &l 1838  8RA £. £ 2 K 2  1  (27)  0  3n *3  In the event that the atom considered has two or more valence electrons direct application of the above expressions  42 B r e i t , G., Phys. Rev., ^,6?i: 43 Racah, G.  1931.  Z e i t s . f .Phys., JL, 431: 1931.  -21i s impossible.  B e t h e l points out that frequently i n t h i s  case the i n t e r a c t i o n i s due t o the presence o f a single penet r a t i n g s e l e c t r o n i n the group o f valence electrons; here the separation f o r a given state can be obtained simply i n terms o f the i n t e r a c t i o n constant o f the s electron. For 2 s-electrons the i n t e r v a l factor can be given by one-half the sum o f the i n d i v i d u a l e l e c t r o n i c factors.  The very much more complicated  cases concerning other configurations have been treated i n great d e t a i l by Crawford, B r e i t , W i l l s and others  45, 4?.  The c h i e f reason advanced f o r the d e t a i l e d study of the hyperfine structure of an element i s that such study i s , as previously mentioned, often instrumental i n the determination o f three very important nuclear properties. The presence o f two of these i s revealed by the holding o f the i n t e r v a l r u l e , that o f the remaining one by departures from t h i s r u l e .  The two cases  w i l l be discussed b r i e f l y . (a)  V a l i d i t y of the i n t e r v a l r u l e .  Already a t our d i s p o s a l i s the f a c t that there e x i s t s l e v e l s f o r I < J , and 2J +1 l e v e l s f o r I > J,  21+1  I being the  resultant nuclear angular momentum o r "spin".  I f the number of  hyperfine components of any hyperfine state i s l e s s than 2J-f i ,  44  Bethe, H., Rev.Mod.Phys.,  8, 206-226:  45  Crawford, M.F., Fhys.Rev., 41,  46  B r e i t , G., and L.A.Wills, Phys .Rev. 4Jt 470:  47  Crawford, M.F., and L.A.Wills, Phys .Rev.  768:  1936. 1935. 1933.  48, 69:  1935.  -22-  one can immediately I.  determine the fundamental nuclear property  Here the so-called " f l a g patterns , i n which the separations 11  decrease uniformly across the pattern, are exceedingly h e l p f u l . In spectra o f the one-election type, there are o f t e n no states of s u f f i c i e n t l y l a r g e J which.have an appreciable hyperfine structure.  By appealing to the i n t e r v a l r u l e one can here determine  the F values o f the hyperfine s t a t e s . Thus, i f J i s known, the spin I can r e a d i l y be found.  The i n t e r v a l rule cannot,  unfortunately, be applied,to a state having J : | . The second o f the nuclear properties which may be determined by u t i l i z a t i o n o f the i n t e r v a l r u l e i s t h e magnetic moment  u j . For the case o f one valence electron, combination  of (23) with (24) and (27) gives the following formulae f o r the magnetic moment:  u  T 1  and  «/ a l * • Z± U + J 0 +1)^1838 — ±I ( £ + 1) K  =  3aln*  3  (28)  1838 (29)  Thus, by experimental determination o f the i n t e r v a l factor a, the magnetic moment can often be r e a d i l y found by (28) or (29). In the event that the atom possesses two o r more valence electrons, the work o f Crawford et a l ( l o c . c i t . ) can be used t o f i n d r e l a t i o n s which give the hyperfine structure s i z e i n terms o f the i n t e r a c t i o n constants of the various electrons involved.  -23'  Then the magnetic moment can be found by again resorting to (28) or ( 2 9 ) .  (b)  Departures from the i n t e r v a l r u l e *  In general hyperfine m u l t i p l e t s obey the i n t e r v a l rule f a r better than do fine-structure m u l t i p l e t s ; t h i s very r e g u l a r i t y makes the few exceptions the more s t r i k i n g .  One explanation  of these exceptions concerns the appearance, i n hyperfine structure, of the perturbation e f f e c t .  Such perturbation  could occur i f two hyperfine l e v e l s s a t i s f i e d c e r t a i n quantum conditions, the most important being that the values o f F be identical.  However, whereas two f i n e - s t r u c t u r e components may  perturb one another when as much as 2000 caT^ apart, the l e v e l s o f the f i n e r structure must l i e but a few u n i t s apart.  There-  fore i t i s much l e s s probable that an unknown l e v e l could l i e i n a p o s i t i o n to produce the observed d i s t o r t i o n . Recently deviations from the i n t e r v a l r u l e have been found f o r which the perturbation e f f e c t i s an inadequate explanation.  Instead of the displacements of the l e v e l s from the  m u l t i p l e t centroid being proportional simply t o the cosine of the angle between  I and  J , a second term, proportional to the  square o f t h i s cosine, appears.  The form such deviations take  suggests that the new disturbing force i s e l e c t r o s t a t i c i n o r i g i n and i s due to a lack o f spherical symmetry i n the nuclear electric f i e l d .  A so-called " e l e c t r i c quadrupole moment" i s  -24th en said to be brought about by the spherical asymmetry of the nuclear protonic charge. Casimir4d  has shown that for a single valence electron the energy change of a hyperfine state P(assodated with the atomic state  j s^-  i) due to the presence of a quadrupole  moment Q can be given by: A V  F  S  - ^  Q  ( 3 cos*e-l)  2  (  i>  )  r3e(c-^i)-^i.i(i^-i)(.i^i)1  l  IJC2I-DC2J-1) IB  where C-F(F-*-l)-I(l+l)-j( j + l )  J ( 3Q)  The quantity |3 cos. d^lj. an 2  t  average over the extra-nuclear electronic charge density, i s to be calculated for each relevant electron configuration. It i s seen from (30) that, for j - ^, 4W  A  equal to zero.  becomes  Thus a quadrupole effect w i l l be absent i n the  case of single S or f | electrons. Also i t can be shown that other states w i l l produce effects which are roughly proportional to the ordinary fine-structure doublet separation; relatively large effects can be expected for the low electrons i n the heavier elements.  recommend ed.  48  p^ and cL  The extension of the theory  to the case of two or more valence electrons i s too to be given here.  therefore  complicated  Careful perusal of the original a r t i c l e i s '  Casimir, H.B.G., Physica,  2,  71&r  1935.  -25By choosing a hyperfine state, therefore, i n which any deviation from the interval rule i s d e f i n i t e l y not due to perturbation effects, one can u t i l i z e such deviation to calculate the quadrupole moment Q of the nucleus. The result can often be used with good effect i n determining the nuclear charge d i s t r i bution;  f o r Q having a positive, negative or zero value indicates  respectively a prolate, oblate, or spherical charge distribution i n the direction of nuclear "spin". C. Isoelectronic Sequences. The term "isoelectronic sequence" refers to a sequence of atoms possessing an i d e n t i c a l number of extra-nuclear electrons but, of course, different nuclear charges. Because of t h i s fact, the energy levels of each atom in. such a sequence, and also the spectral l i n e s resulting from transitions between these levels, show surprising s i m i l a r i t i e s from element to element.  Millikan  and Bowen^ and others have shown that the regular - and i r r e gular - doublet laws of X-ray spectra could be applied to the optical doublets produced by a l k a l i - l i k e atoms. The application of these laws to a l k a l i doublets w i l l be discussed here i n some detail.  49 M i l l i k a n , B.A., and LS.Bowen, Phys .Rev. 24., 209: 1924.  -26(a)  The Irregular o r Screening-Doublet  Law.  50  This law was discovered i n 1920 by Hertz-  who had observed  p a r a l l e l l i n e s i n an X-ray l e v e l scheme.  The law, which a p p l i e s  to those l e v e l s having the same n, S and J values, but values of L d i f f e r i n g by unity, can be given - i n i t s extension t o i s o e l e c t r o n i c sequences - thus:  The difference between the  square roots o f the term values of Hie l e v e l s having the same p r i n c i p a l quantum number n i s independent o f the atomic number £ • The formulation o f i b i s r u l e can be simply given i n the following manner.  From the term-value R  T ;  (  Z  ~ /  )  equation o f Hertz  2  (  3  1  )  (where <ris the screening constant accounting f o r the d i f f e r e n c e between the term values of any atoms and those of hydrogen-like atoms given by  RZ  T -  JJZ  /X V  With  and <T  Z  r  V  hcR  ) "  one obtains _ i _ n  ( 2 - ^  the screening constants f o r the two l e v e l s of  a doublet, the term difference between t h e l e v e l s can be given by A/X * R  50  =  c;~ <r^ ~ — —  n.  Hertz, G., Z e i t s .  —  A(T  f.Phys.  n  ~  19:  a constant  1920.  (32)  -27The following s o - c a l l e d "Moseley Diagram" depicts the v a l i d i t y of the irregular-doublet law f o r a t y p i c a l 3-electron system.  The doublet f i n e - s t r u c t u r e separations are so small i n t h i s system that they are omitted i n the f i g u r e .  (The dotted l i n e s  represent the i d e a l "hydrogen-like" condition that the two K electrons l i e close enough to the nucleus to reduce the nuclear charge by two).  I t i s to be observed that the p l o t t e d l i n e s have  t h e i r slopes c l o s e l y equal t o 1, and that l e v e l s with the same n n are c l o s e l y p a r a l l e l , i n good agreement with the demands of the theory.  The heavier the element, i . e . the greater the  nuclear charge, the more pronounced become the deviations of the l i n e slopes from the value 1. n A second, and often more u s e f u l , form of the  -28i r r e g u l a r doublet law i s given by the following statement: The frequency differences between two l e v e l s having the same value o f n are l i n e a r functions o f the atomic number 2 .  This  condition a r i s e s from the f a c t that, while s e l e c t i o n r u l e s do' not allow both l e v e l s o f a screening doublet t o combine with a t h i r d l e v e l , the two are permitted t o combine together.  Such  t r a n s i t i o n s have not as yet been observed i n X-ray spectra, probably because of the low i n t e n s i t y o f the r e s u l t i n g l i n e s ; however, they have been observed i n o p t i c a l spectra.  The  deri&tion o f t h i s second form o f the irregular-doublet law can be given as follows.  In an i s o e l e c t r o n i c sequence, a p a i r o f  "Moseley l i n e s " may be written as  I f the l i n e s are p a r a l l e l ,  -  =  n.  Thus the frequency of  the r e s u l t i n g l i n e w i l l be given by:  C 2 x  -h  (33)  This form of the irregular-doublet law i s therefore invaluable f o r predicting frequencies and wave-lengths o f u n i d e n t i f i e d l i n e s i n multiply ionized atoms. (b)  The Regular-Doublet Law.  -29Th e term  M  s p i n - r e l a t i v i t y " doublet or "regular" doublet  r e f e r s t o a p a i r o f energy l e v e l s having the same n, S and L values, but values o f J d i f f e r i n g by u n i t y . law can be stated i n the following form:  The regular doublet  The doublet separation  Av, i n wave numbers, i s approximately proportional to the fourth power of the e f f e c t i v e quantum number  2 - s, where  s  isa  screening constant expressing, as before, the s h i e l d i n g e f f e c t of the closed electron sub-shells.  Sommerfeld, using the concept of  the r e l a t i v i s t i c change of electron mass with v e l o c i t y , was able to determine the mathematical form o f the law. The formula, written i n modern quantum notation, i s given t o a f i r s t approximation by Av  „  2,„  N  4  -1  (34)  Z R<* CZ - s) cm. XL JL (1+1) 3  I t was applied o r i g i n a l l y to the theory of hydrogen f i n e - s t r u c t u r e and of X-rays; s t i l l l a t e r i t was applied by M i l l i k a n and Bowen to o p t i c a l doublets.  I t i s t o be noted t h a t t h i s formula i s  i d e n t i c a l with the one, given by ( 9 ) , i n whose derivation the more recent concept of electron spin was u t i l i z e d * The a p p l i c a t i o n o f t h e formula t o o p t i c a l doublets i n i s o e l e c t r o n i c sequences showed that the screening constant decreases s l i g h t l y but regularly as Z increases; and, while  s s  i s quite regular w i t h i n a s i n g l e i s o e l e c t r o n i c group, i t varies from sequence to sequence i n a t o t a l l y i r r e g u l a r manner*  The formula,  of course, w i l l hold only f o r the case of non-penetrating o r b i t s  o f the valence electron. The above theory i s quite adequate f o r elements i n the short periods.  For the long periods, however, another formula  has been found to give more s a t i s f a c t o r y r e s u l t s .  I t may  be  mentioned here that Sommerfeld developed h i s doublet formula on the assumption that the o p t i c a l l y active electron moves i n a uniform f i e l d equal to that of a point charge  ( Z-  s)£.  A  refinement of the theory which gives b e t t e r r e s u l t s i n the case of the so-called penetrating o r b i t s advocates use of the Lande doublet formula previously given by equations (10) and (11)  A\t zR°? Z  Z  2  i  -  2  o  Roc ( Z - 5 ) 2  (2-S )2  2  ±  c  -  as  cm;l  ,  n*3i(i+i)  n  1(1+1)  *3  where n * , the e f f e c t i v e quantum number, w i l l d i f f e r by a r e l a t i v e l y large amount from n. The values of S± -  2 - Z±  should, f o r P terms,  t h e o r e t i c a l l y l i e between 2 and 10 to account f o r screening o f the nucleus by the K s h e l l of planetary by part of the L s h e l l as w e l l . should give values of  electrons and perhaps  By s i m i l a r reasoning, D terms  S± greater than 10.  In most cases the  Lande formula confirms these assumptions by giving r e s u l t s of the proper order  (Table I I c . ( l ) ) .  The formula i s also u s e f u l  i n that i t v e r i f i e s two seemingly unrelated empirical rules of spectroscopy, namely that:  -31(I)  In a sequence of i s o e l e c t r o n i c spectra, the doublet  i n t e r v a l w i l l be approximately proportional to Zo, n  vary but l i t t l e throughout the sequence,  since-2^  (Table I I c.(l)).  (II) Inside a single term sequence, the doublet i n t e r v a l decreases roughly i n the r a t i o  1  n  (Table I I c.(2) ) .  -32-  IV  A.  EXPERIMENTAL  The ELectrodeless Discharge* The electrodeless discharge has been used - as a  method o f exciting the arc andspark spectra o f various e l e ments - with great success by several investigators-* . 1  The main  advantages of t h i s type of l i g h t source are twofold: (1)  The excitation can be controlled i n some degree by the  strength and frequency of the source current, and (2)  The pressure broadening o f the spectral l i n e s can be  reduced t o a minimum, thus ensuring more accurate determination of the wave-lengths of these l i n e s . In t h i s means o f e x c i t a t i o n , the gaseous discharge i s , as the name suggests, maintained i n a closed tube without electrodes.  The tube i s placed within a c o i l carrying a high-frequency  current, which may be generated by a vacuum-tube o s c i l l a t o r o r , as i n the present investigations, by the c i r c u i t t o be described presently.  The current i n the c o i l sets up an o s c i l l a t i n g high-  frequency e l e c t r i c f i e l d within the tube;  t h i s f i e l d produces  s u f f i c i e n t electron v e l o c i t y t o excite the atoms or molecules of the vapor within the v e s s e l .  The electron v e l o c i t i e s depend upon  the f i e l d strength, the length o f time of a p p l i c a t i o n o f the  51 e.g. Bares, W., Thesis, The Spectra o f Iodine, The University of B r i t i s h Columbia, A p r i l , 1939.  f i e l d , and the distance an electron can t r a v e l before c o l l i d i n g with a molecule.  These factors can be controlled by adjusting  both the strength and frequency o f the current and the gas pressure.  Lower pressures w i l l i n general give r i s e t o greater  excitations because o f the l a r g e r amount o f energy obtained by the  electron i n the r e s u l t i n g greater mean free path.  Thus any  gas, or any metal which may be vaporized by temperatures t o which the  tube can be subjected, can be studied i n the above manner. The discharge tube used i n the present i n v e s t i g a t i o n s  was constructed o f translucent quartz combustion tubing; i t measured about 35 centimetres i n length and 2.5 centimetres i n diameter.  The type o f tubing used was required because o f the  r e l a t i v e l y high temperatures needed f o r the vaporization o f Cadmium:(whose b o i l i n g point i s 767°C).  Clear, f l a t quartz  windows were fused t o the ends o f the v e s s e l , and a side tube was provided near one end. The work was done by Mr.A.W.Pye of the  Physics Department workshop o f t h i s u n i v e r s i t y . The e x c i t a t i o n c o i l - denoted by A i n Plate I -  consisted of about twelve turns o f #12 bare copper wire; i t was separated from the discharge tube i t s e l f by a t h i n sheath of mica.  The experimental arrangement permitted the c o i l t o  be e a s i l y detached - a t B and B  1  - from the remainder o f the  circuit. The transformer T possessed a secondary winding giving a voltage output o f approximately 100KV with a power  -34-  rating o f about 6KVA.  A heavy-duty control rheostat E of 3 - 1 2  ohms was placed i n series with the transformer primary, i t s e l f connected across a 1 1 0 - v o l t A.C.supply.  The e x c i t a t i o n currents  used could thus vary i n range from about 10 to a maximum o f over 30 amperes. The capacitance C o f the c i r c u i t consisted of 4 large Leyden j a r s constructed by shellacing t i n f o i l to Pyrex containers. These j a r s are connected, i n p a r a l l e l , as shown.  The spark gap S  consisted o f two i r o n cones and u t i l i z e d a screw arrangement permitting the size o f the gap t o be varied a t w i l l .  The leads i n  the c i r c u i t were kept as short as possible t o prevent any undesirable capacitance e f f e c t s .  B. The Spectrograph. Spectrograms o f the r a d i a t i o n were made on a Hilger £ 1 Quartz Litttow-type  spectrograph having a f o c a l length of 165  centimetres f o r the sodium D - l i n e . Because o f i t s quartz o p t i c s , t h i s instrument could be used i n both the v i s i b l e and u l t r a v i o l e t regions o f the spectrum.  The dispersion ranged from  about 1 . 5 A/mm. a t 2000 A. to about 50 S/mm.  at 68O0X.  Before the focussing proper o f the spectrograph could be undertaken, i t was necessary t o locate the l i g h t source upon the o p t i c a x i s of the collimating l e n s . doing i s given by Sawyer-* . 2  52  A simple method f o r so  The i l l u m i n a t i o n used i n t h i s and  Sawyer, E.A.Experimental  Spectroscopy, Prentice-Hall, 1944.  -35the following adjustments, an ordinary i r o n arc, was selected because i t provided a good number of intense l i n e s w e l l d i s t r i b u t e d throughout the spectrum. In the present model o f the spectrograph there were three variables to be considered i n the focussing, namely: (1)  The prism r o t a t i o n  (2)  The prism t r a n s l a t i o n , and  (3) The plate-holder r o t a t i o n . These settings oould not be f i x e d f o r any one s p e c t r a l region because o f the e f f e c t on them o f temperature and pressure variations. A f t e r the desired region had been established on the prism r o t a t i o n drum, the approximate s e t t i n g o f the prism t r a n s l a t i o n and of the plate-holder r o t a t i o n could be made visually.  The f i n a l accurate s e t t i n g o f the prism t r a n s l a t i o n  was made photographically - by the taking o f a series o f equally-spaced  exposures i n the region o f best focus.  The  necessary amount o f plate-holder r o t a t i o n t o g i v e the correct plate t i l t could then be interpolated i n turn from these exposures.  The taking o f another p l a t e - t h i s time u t i l i z i n g  the discharge i t s e l f - t o discover the best exposure times generally completed the adjustment o f the spectrograph.  This  s l i t was v i s u a l l y adjusted t o optimum width, and l e f t unchanged f o r a l l regions.  -36-  Q. Operation of the Source. The tube was positioned, as depicted i n Plates I I and I I I , by plywood stands which held the tube spectrograph s l i t .  c o a x i a l with the  The m e t a l l i c Cadmium to be vaporized was  introduced i n t o the discharge v e s s e l by means o f small fragments. These fragments were concentrated at the centre of the tube, which was then connected to a Megavac pump producing a pressure of only 10"Anm. o f mercury.  I t was found that s u f f i c i e n t e x c i t a t i o n  could not be achieved by the applied e l e c t r i c f i e l d alone.  A  source o f heat, i n the form o f an ordinary Bunsen burner, was therefore u t i l i z e d .  The burner was also equipped with a  " f i s h - t a i l " cap - as c l e a r l y shown i n plate I I I - to help l o c a l i z e the heat upon the p o r t i o n of the tube i n which the Cadmium was concentrated* Even more e f f e c t i v e use o f the heat was obtained by enclosing the discharge tube i n a "box" - open at the bottom - made of Transite board.  This arrangement, shown  i n Plate I I , reduced the l o s s o f flame heat by r a d i a t i o n and other means. Wiring the burner to the remainder o f the c i r c u i t prevented any sparking which might occur because o f the proximity of c o i l and burner.  I t was found necessary t o evacuate the tube  quite thoroughly before the e l e c t r i c f i e l d and the heat were applied;  otherwise a deposit o f Cadmium Oxide would produce a  s t a i n , upon the quartz end windows, which was almost impossible of  removal.  -37The vapor pressure i n the tube was controlled quite adequately by means o f a v a r i a b l e pinch-clamp attached t o the pump 8 rubber intake tube. 1  To s t a r t the discharge, i t was  found necessary t o "clamp o f f " the tube from the pump so that the cadmium vapor pressure could- be b u i l t up. . Upon examination o f the ensuing r a d i a t i o n with a  hand spectroscope, one could  adjust the pressure and the current strength t o give the maximum e x c i t a t i o n and i n t e n s i t y .  During the p l a t e exposures, the  tube's end windows were often "fogged" by a f i l m o f Cadmium; t h i s condition seriously reduced the i n t e n s i t y of the r a d i a t i o n from the tube.  The windows, however, could be cleared quite  adequately by the a p p l i c a t i o n ..for a few seconds, o f a Bunsen flame.  D. Exposure and Measurement o f P l a t e s . When the above work was completed, three s p e c t r a l regions of the e x c i t a t i o n were photographed - namely 6800t  3300A, 33008 - 25008 and 25008 - 200o8.  -  The plates used i n the  f i r s t two regions were o f the Eastmann II-F type; i n the l a s t mentioned region results.  I l f o r d QI plates were found to give excellent  The thinness o f the emulsion used i n the l a t t e r type,  however, necessitated very c a r e f u l handling i n order to avoid scratching. An exposure time o f between 3 i and 5 minutes, depending upon the f l u c t u a t i o n s i n the i n t e n s i t y of the discharge, was  -38found to be s u f f i c i e n t f o r a l l regions photographed.  The  exposures were taken at f u l l s l i t length, and i n the centre of each was  superposed a  comparison spectrum.  This l a t t e r  was obtained by decreasing the s l i t length and then  shining  a x i a l l y through the discharge tube the l i g h t of e i t h e r an i r o n arc ( f o r the regions 68O08 copper arc ( f o r the region  330o8 and 330G-2 - 25008) or o f a  2500-8  -  200oX).  An exposure time  of about 25 seconds was found to s u f f i c e f o r the i r o n a r c , while f o r the copper a period of about 3 minutes was needed. In Plate IV i s shown a sample spectrogram (of the region  68008 - 33008). The positions of the l i n e s on the best p l a t e f o r each region were measured by means o f a to .001 mm.  Hilger comparator reading  The wave-lengths of a l l "prospective  11  Cadmium  l i n e s were calculated by means o f the standard Hartmann formula:  ar a+  £—  0  d  + do  The comparison spectra were used merely f o r tentative i d e n t i f i c a t i o n of l i n e s and not as "Hartmann standards"; t h i s r e s t r i c t i o n was due t o the f a c t t h a t a difference i n exposure times^admium and of comparison spectra produced, because o f temperature e f f e c t s , a s l i g h t r e l a t i v e s h i f t between l i n e s of the two spectra.  To f a c i l i t a t e the i d e n t i -  -39 f i c a t i o n of Cadmium "Hartmann standards", a dispersion curve f o r the H i l g e r spectrograph was drawn up (Plate V ) .  V.  A.  RESULTS  Results o f Wave-length Measurements* The wave-lengths o f approximately 330 l i n e s appearing  on the plates covering the three regions were measured by the means previously described*  In Table I , the following r e s u l t i n g  information on the Cadmium spectra i s given: (1)  The state of i o n i z a t i o n , where known, giving r i s e  to the relevant l i n e . (2)  The i n t e n s i t y o f each l i n e , obtained by v i s u a l means;  the i n t e n s i t y scale ranges from 0 f o r exceptionally weak l i n e s to 10 f o r very strong ones* (3)  The wave-lengths ( i n a i r ) i n A.ttj these are o f two kinds;  (a) Those - about 150 i n number - whose values were found t o agree with values given by previous investigators. (b) A few - about 21 - whose values agreed neither with any Cadmium wave-lengths (known a t t h i s writing) nor with the wave-lengths of any possible impurity l i n e s . (4)  Remarks, l i s t i n g as "new" the type of l i n e mentioned  i n 3(b). The work done corroborates the f a c t o f the r e l a t i v e paucity of l i n e s i n the Cadmium spectrum. were concentrated i n the range  ^The so-called "new" l i n e s  60008 -  3900&;  and very few  -41Cadmium I I I l i n e s j and bat one Cadmium IV l i n e , were excited. The impurity l i n e s and bands were, throughout the whole spectrum, produced mainly by the c h i e f constituents o f a i r , i . e . oxygen, nitrogen, and the i n e r t gases. B. Investigations o f Isoelectronic Sequences. I t i s r e a d i l y seen from theory that the hyperfine i n t e r v a l s occurring i n the spark spectra of an element w i l l be l a r g e r than those associated with the arc spectrum; has been generally confirmed by experiment.  Thus a study o f the  hyperfine structure of, i n t h i s case, Cd I I , should a f a r more accurate determination magnetic moments o f Cadmium.  t h i s fact  facilitate  o f t h e nuclear mechanical and  A study of the i s o e l e c t r o n i c  sequence Agl, Cd I I , I n d . I l l , Sn IV and Sb V was therefore undertaken i n the b e l i e f that i t would prove valuable i n the necessary preliminary study o f the grosser spectral structure of Cd I I .  Also the v a l i d i t y o f the various aspects o f the  regular - and i r r e g u l a r - doublet laws could be tested i n the case of such an exemplifying  sequence.  Tables IIA, IIB, and A  I I C ( l ) represent term tables f o r the above " s i l v e r - l i k e " i s o e l e c t r o n i c group.  Plates VI, V I I and V H I g r a p h i c a l l y  i l l u s t r a t e the form o f the doublet laws.  Plates IX and X  i l l u s t r a t e two forms o f the energy l e v e l diagram; the l a t t e r form i s e s p e c i a l l y u s e f u l i n evaluating terms and l i m i t s of spectral series.  (To add to the general information  concerning  -42-  the various Cadmium spectra, an energy l e v e l diagram of Cdl has also been prepared - from the r e s u l t s o f Table H E ) . The above work has availed i t s e l f o f the published material o f Pauling and Goudsmit^.  53 Pauling, L., and S.A.Goudsmit, The Structure o f Line Spectra, McGraw-Hill, 1930.  TABLE  ORIGIN  INT.  Cd I Cd I I Cd I I Cd I I Cd I Cd I I Cd I I Cd I Cd I Cd I Cd Cd Cd I I Cd Cd Cd Cd Cd I I Cd I I Cd Cd I Cd I Cd I Cd I Cd I I Cd Cd Cd I I Cd I Cd I I Cd Cd Cd Cd Cd I I Cd Cd I I Cd I I Cd Cd  3 6 10 4 10 6 4 4 5 5 1 0 6 2 1 1 2 10 7 1 9 10 10 0 1 1 10 4 2 2 1 4 3 1 4 4 8 1 4 0  A air  6778.10 6759.26 6725.83 6464.98 6438.4696 6359.93 6354.72 6325.19 6111.52 6099.18 6003.03 5938.34 5843.175 5796.51 5780.47 5664.90 5393.92 5381.82 5337.492  REMARKS  new new new new new new  new  4148.51 4141.58 4140.50 4134.78 4130.57 4126.20  new  4123.72  ORIGIN Cd I I Cd I I Cd Cd Cd Cd I I Cd Cd  5311.57 5085.824 4799.918 4678.156 4614.17 4605.81 4511.34 4414.63 4412.31 4302.82 4285.07 4278.03 4245.869 4243.39  I  new  new new  Cd Cd Cd I I Cd Cd Cd I I Cd Cd I I Cd I Cd I I I Cd I Cd I Cd I Cd Cd I I Cd I I I Cd I I Cd Cd I Cd I I Cd I I I Cd I I Cd I Cd I Cd I I Cd I I Cd I I Cd I I Cd I I Cd n Cd I I  INT.  6 3  3 0 7 1 1  3 4 7 2 3 3 4 4 2 1 7 9 10 3 8 0 1 2 3 9 1 1 10 10 8 0 0 2 7 0 4  A air  4102.00 4094.50 4091.22 4049.15 4043.20 4029.08 4017.98 4006.68 3993.80 3977.47 3957.40 3950.45 3935.09 3827.41  REMARKS  new new new new new new new new  3776.32  3768.10 3649.597 3626.70 3614.45 3612.875 3610.51 3576.51 3535.687 3529.80 3524.072 3518.99 3500.00 3495.34 3486.00 3483.04 3467.656 3466.201 3464.37 3422.964 3420.16 3417.396 3402.16 3388.85 3385.40  new  TABLE I  ORIGIN Cd Cd Cd Cd II Cd III Cd III Cd I I Cd I Cd I Cd II Cd II Cd III Cd I I Cd I I Cd Cd Cd I Cd Cd III Cd III Gd Cd Cd II Cd I I Cd Cd I Cd I I Cd Cd II Cd III Cd III Cd I I Cd III Cd I Cd I Cd III Cd I Cd III Cd II Cd IV  INT, 1 4 3 2 1 2 0 9 10 4 10 5 2 0 0 2 9 2 2 2 2 3 1 0 3 8 1 3 1 0 1 0 0 10 10 0 1 1 2 2  ^air 3385.346 3370.91 3359.82 3343.15 3333.20 3283.82 3279.17 3261.057 3252.525 3250.301 3250.17 3217.80 3185.55 3174.489 3173.613 3160.814 3133.167 3129.206 3124.4 3121.80 3118.915 3095.45 3092.393 3089.856 3084.866 3080.827 3068.790 3064.955 3059.22 3053.10 3048.82 3008.02 2987.20 2981.89 2981.34 2971.20 2961.47 2948.16 2929.285 2919.13  REMARKS  new  ORIGIN  Cd II Cd I Cd I Cd I Cd I Cd. I I Cd I I Cd III Cd I Cd II Cd I Cd II Cd I Cd I Cd I I Cd I Cd I Cd I Cd 1 Cd I Cd I Cd I Cd I Cd II Cd I I Cd I Cd I I Cd I I Cd I I Cd I I Cd II Cd II Cd III Cd Cd I I Cd I I Cd II  INT. ^ a i r  1 10 6 1 9 10 5 2 5 1 10 9 3 3 1 10 $ 7 1 2 5 0 7 10 8 2 2 5 2 8 3 1 5 6 5 4 1  2914.69 2880.77 2868.26 2862.31 2836.907 2834.19 2823.19 2780.28 2775.047 2767.49 2763.89 2748.58 2733.86 2712.57 2707.1A 2677.64 2660.40 2639.50 2632.244 2629.05 2602.18 2592.14 2580|30 2573.09 2552.18 2544.71 2509.25 2495.73 2470.61 2469.84 2419.40 2377.63 2350.30 2329.282 2321.15 2312.84 2295.32  REMARKS  TABLE I  ORIGIN Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd Cd  I II II II II II II II II II II  INT.  A air  9 0 2 9 5 0 4 2 6 8 1 5 9 3 3 7 1  2288.018 2272.38 2267.47 2265.017 2239.86 2236.32 2210.37 2195.35 2194.63 2188.55 2176.88 2155.70 2144.382 2129.12 2112.17 2096.63 2036.79  REMARKS  TABLE  ajT  FIRST FORM OF IRREGULAR-DOUBLET LAW:  (1) Config.  Atom  %  (2)  4d  10  5s -  2  S|  4d  10  HA Independent of 2, An -  ^  (3)  5p - P ° £  4d  2  r(cm-i)  T(cm-i)  (4J Config.  Atom  4d  Z  10  247 379 476 573 670  .746 1.115 1.435 1.73 .2.02  31552.1 92241.3 168948 259112 367734  6s  T(cm~J)  Agl 47 18548.5 Cd II 48 53386.4 I n d i u m 99255 Sn IV 50 154540 Sb V 51. 224713  -  2  .536 .920 1.240 1.535 1.83  177i5. 304 411 509 606  (5) 4d 6p - 2P°|  n  I VE 1  136 .411 231 .697 315 .952 393 1.189 473 1.435  jCcm" ) 1  12808.2 41665.8 81545 130826  -  5p  - F°3_ 2  JT/R  1  -  .528 .90 1.23 1.52 1.81  175 299 406 503 598  2  j VR 113 204 286 362  30631.5 89758.1 164606 252594 358746  4d-10 6p ... p o  1G  S|  10  Ttcm-l)  ^R  Ag I 47 61104.4 Cd II 48 135376.6 Ind.III49 226133 Sn IV 50 328671 Sb V 51 449300  0.  T(cm~V)  .342 .618 .864 1.09  -  12604.3 40992.5 80208 128649  -  3 / 2  V  112.3 202 283 359  -  R .339 .611 .856 1.08  -  TABLE  IIA  FIRST FORM OF IRREGULAR-DOUBLET. LAW:  (Continued) independent of 2,  A]T R  An . 0 .  V  (8)  (7) Config.  Ad  Atom  2  Ag I  47  1 0  l U m - l ]). 12360  Cd I I 48 46685.3 I n d l l l 49  Sn I V  Sb V  5d  97675  50 1 6 3 3 7 4  51 247393  -  J T  2  D  3/2  J W  111.2 .318 215.8 .653 312.5 .945 404.2 1.22 497.4 1.50  4d  1 0  T(cm-l)  12339.9 46531.0 97385 163267 246564  5d  (9) -  JT  111.1 215.7 312.1 404.1 496.6  2  D  5/2  JW& .318  .651 ..944 1.22 1.50  4d  1 0  T(em-l)  9217.3 29077.1 56706 91063 •*  7s - Sh 2  J T  95  170.5  238  302  .290 .516 .719 .913  TABLE- IIA  (Continued)  FIRST FORM OF IRREGULAR-DOUBLET LAW:  (10)  .  %  Kern"*})  Ag I 47 Cd I I 48 I n d l l l 49 Sn IV 50 Sb V 51  6899.8 26202.1 55602 93885  Atom  2  1G  JT/R  JT  83 .250 161.8 .488 235.8 .711 306.4 .923  4d 6d  4d  Atom  TUm-})  Ag I 47 Cd I I 48 I n d l l l 49 Sn IV 50 Sb V 51  6990.4 27955.1 64154 211243  -  2  D  5/2  J T  T(cm~!)  6890.5 26128.6 55420 93553  83  161.7 235.4 ' 305.8  JT7R .251 .487  .710 .925  (13)  Config. jg  -  10  (12) 10  independent of 2,-An = 0.  (11)  4d 6d -- D3/2  ConfiK.  jTyR  4f  " *°5/2 2  JT/R  83.6 .252 167.2 .504 253 .765 460 1.39  -  4 d 4f 10  -  2F°7/2 JT/R  X(cm"i) 6990.4 27942.3 64154 211231  -  83.6 167.2 253 460  -  .252 .504 .765 1.39  -  TABLE  HB  ALTERNATIVE FORM OF IRREGDLAR-DOUBLET LAW (V  a l i n e a r function of Z)  TRANSITION  V(CM."' ) Ag I  A  4 d 5 s S i - 4dl05p 2 p |  B  4d 6s S i - 4d 6p  C  4dl05p P2. - 4 d 5 d D3_ 2 2  D  4 d 6 s S f - 4 d 6 d 2D3_ 2  10  2  Cd I I  Indlll  Sn IV  Sb V  29552,3  44135.3  57185.0  69559.0 81566.0  5943.7  12393*9  19047.0  25891.0  18291.6  43227*1  67221.0  89327.0; 112182.0;  11648.7  27184.3  43653.0  60655.0  Jo 10  2  2  10  2  10  10  10  2  P|  2  '  TABLE REGULAR-DOUBLET LAW:  Configuration  4d 6p  4V .  10  ^V(cm-l)  Atom  Agl Cdll Indlll SnIV SbV  47 48 49 50  51  Configuration  203.4 673.3 1337 2177  2.927 3.246 3.480 3.663  4d 5p 10  Atom (observed) Agl Cdll Indlll SnIV SbV  47 48 49 50  51  920.6 2483.2 4342 6518 8988  4V  n 1.865 2.181 2.418 2.602 2.731  p| - P|  4d  2  3.073 2.754 2.520 2.337  -  (1)  Application of Lande Doublet Formula t o Second Long Period  u n - n  n'  observed  2  IIC  / 2  Z~  s Z-Z i =  1 2 3 4 5  46 46 46 46 46  41.87 44.38 46.38 47.94  ±  5.13  3.62 2.62 2.06  10  aV = ^ 7 2  6d  k¥(cri~-) Observed  9.3 73.5 182 332  2o P  i  u= n-n  3.135 2.819 2.582 2.398 2.269  5/2 o= Z-Z, S  1 2 3 4 5  46 46 46 46 46  Si s  Z-Z  ±  45.31 1.69 47.00 1.00 48.43 .57 49.71 .29 50.16 .84  u n-n* =  3.988 4.093 4.214 4.324  2.012 1.907 1.786 1.676  ^5/2 Z o  s -  z\ 46 46 46 46 46  Z. 1  Z-s,  24.66 22.34 36.04 11.96 39.50 9.5 8.41 41.59  TABLE U C (2) CADMIUM n  p  2  n*  -  Config.AY em-1. •n #3 (4*Pf -|)  5p 6p 7p 8p 9p  2483.2 10.37 673.3 34.20 115.4 78.24 54.4 147.5 31.6 246.9  -lx Config. AV( cm'  5d 6d 7d 8d 9d lOd  ,*3  .2 2 154.3 28.82 73.5 68.57 39.8 132.9 23.5 14.9 228 9.9 359.7 534.2  TABLE LTD TERM TABLE FOR. AG-LIKE lSCELF™nwTn AG I Config  Symbol J  < = ?z 0 4d^5s 5p  -pO  6s 6p  2 2po  1 2  S  5d  2  7s 4f  I  6d  2  8s 7d  2 2D  5f  2po  9s 8d  ?D  D  3  D  S  2  S  f  3/2 g 3/2 5/2  £ 5/2, 7/2 3/2 5/2 *  3/2 5/2 V2, 7/2  1  3/2 5/2  CD U  (Z-47)  Term Value (cm"!)  STayngame  n  *•  Config  J  Symbol  n  *  •  61104.4 31552a 30631.5  1.340 1.865 1.893  4d 5s  18548.5  4d 5s  6900.4  2.432 2.927 2.951 2.980 2.982 3.450 3.988  6899.8 6890.5 5523.3 4404.1 4398.6  3.988 3.991 4.457 4.992 4.995  78 4f  S 2  6d  2n  4394.8  4.997  7P  2po  3680.5 3054.6 3050.9  5.460 5.994 5.998  8s 5f  2S 2po  12604.8 12360.0 12339.9 9217.3  Term Value (cm" ) 1  2 )  12808.2  (Z«4B)  10  5F  9  2  4d 6s 5d 10  6  P.  2 2po S  2  D  2 2D S  2po  F  0  1  i  136376.6 92241.3 89758.1  1.794 2.ia 2.211  34094 23060 22440  3/2 5/2  67117.8 61483.0 53386.4 46685.8 46531.0 41665.8 40992.5  2.551 2.672 2.867 3.066 3.071 3.246 3.272  16779 15371 13347 11671 11633 10416 10248  £  29077.I 27955.1 27942.3 26202.1 26128.6  3.885 3.962 3.963 4.093 4.099  7269 6989 6986 6551 6532  A. s 3/2  24001.7  4.277  6000  23886.3 18335.5 17828.7  4.287 4.893 4.962  5972 4584 4457  i  3/2 5/2  *  3/2 2  I*  5/2 7/2 3/2 5/2  i  5/2  TABLE IID AG I ifig  Symbol  J  Continued....  (2°47)  Term Value (cm-1) =T/ 2)  CD II (?*4B) n*  Config  Symbol  J  (  Z  Term Value (cm- ) 1  n*  b 10s 9d  2 2D  3/2  i  f  S  lis lOd  2  12s lid  ?  12d  2  2  S  D  S  D D  h  3/2 5/2  *•  3/2 5/2 3/2  2626.7 2241*7 2239.9 1968,0 1714.9 1713.8 1524.8 1353.9 1353.4 1100.5  T 0  6.464 6.997 6.999 7.467 7.999 8.002 8.4845 9.003 9.005 9.986  5g  2G  7d  2D  8p  2po  9a 6f  2S 2po  6g  2G  8d  2D  9p  2po  10s 7f  2 2po S  7/2 7/2, 9/2 3/2 5/2  *  3/2 £  5/2 7/2 7/2, 9/2 3/2 5/2 A  2 3/2  5/2 7/2  17624.0  4.991  4406  16854.0 16814.2 15722.4 15668.0 12624.3 12386.8 12403.0 12223.2  5.103 5.109 •5.284 5.293 5.896 5.953 5.949  4214 4204 3931 3917 3157 3097 3101  5.993  3056  11762.4 11738.9 11151.4 11119.8 9223.2 9092.5 9126.5  6.109 6.115 6.274 6.283 6.899 6.948 6.935  2941 2935 2788 2780 2306 2273 2282  TABLE CD I I ( 2 = 48 ) Config  4d 7g 10  9d lis 8f 8g lOd 12s lid  Symbol j  2Q D  2  2  2 2  (Continued)  Continued  Term Value  (CM-T)  7/2, 8977>9 9/2 8678.8 2 3/2 5/2 8663.9 i 7033.8 S e 2F° 5/2 6957.5 7/2 2G 7/2, 6872.1 9/2 6667.6 D 3/2 5/2 6657.7 S 5540.6 h D 3/2 5275.8 5/2 5283.3  IID  T  Config  Symbol  j  Term Value  (car* )  n  6.992 2244  4d 5s  2169 2166 1758 1739  5P  7.U2 7.118 7.900 7.943  10  2  S  2po  4f  2F©  5d  2  D  7.992 1718 8.114 1667 8.120 1664 8.901 1385 9.122 1319 9.115 1321  6s 6p 5f 6d 7e 6f 6g  2  S.  2po 2o F  2  D  S 2po  2  £  328671  2.311  20542  i 3/2 5/2 7/2 3/2  259112 252594 211243 211231 163374  16194 15787 13203 13202 10211  5/2  163267  2.603 2.6365 2.883 2.883 3.278 3.280  £  154540 130826 128649 115411 115246 93885 93553 91063  3.370 3.663 3.694 3.900 3.903 4.324 4.332 4.391  9659 8177 8041 7213 7203 5868 5847 5691  74993  4.839  4687  4.994  4400  3/2 5/2 7/2 3/2 5/2 i 5/2, 7/2 7/2, 9/2  704CO  10204  TABLE IND Config  Symbol j  1 0  2  5 8  Term Value  n  5P 6s 5d  2  P°  S  2  2  64154  3.924  7128  56706 55602 55420  4.173 4.214 4.221  6301 6178 6158  40320  4.949  4480  39600  4.994  4400  £  36738  5.185  4082  5/2) 7/2,  35833  5.250  3981  27471  5.996  3052  |  3/2  3/2 5  6p 4f  2  7s 6d  2  |  „ Fo  3/2 5/2, 7/2  9  2  s  £  D 0  5f 5g 8s 7d  2  F° ^  2  S  2 9  6g  /  2  Po  2  ^  D  Config  3/2 5/2 5/2, 7/2  3/2) 9/2  226133 168948 164606 99255 97675 97385  Symbol  Z o  81545 80208  i £  D  SB  2.090 25126 2.418 18772 2.449 18289 3.154 11028 3.180 10853 3.184 10821 3.480 9061 3.509 8912  s  (Continued)  I I I ( 2 a 49)  (CM-1)  4d  LTD  10  5p 5d  1  s  2po  j  5  6s 4f  2  Z  (BTl)  449300 367734 3/2 358746 2fl 3/2 247393 246564 o / 2S £ 224713 F ° 5/2, 7/2 180973 2  ( - 31)  Term Value J  4d 5s  V  2  3.336 3.494  17972 14709 14350 9896 9863 8989  3.893  7239  2.471 2.731 2.765  3.330  TABLE TERM TABLE.FOR CADMIUM.I. -  Config  2 >5p 5P  6s 6s 6p 5d 5d 6p 7s 7s  7p  6d 6d  Symbol  h  3po lpo  3s  !S 3po ID  3D lpO  % 3po X  D  3D  J  0 0 1 2 1 1 0 0 1 2 2 1 2 3 1 1 0 0 1 2 2 1 • 2 3  Term.Value (CM**)  II E GIVING EFFECTIVE QUANTUM NOS. n*  1  72538.8 42424.5 41882.6 40711.5 28846.6 21054.7 19229.3 14147.9 14077.2 13903*1 13319.2 13052.4 13040.7 13022.5 12633.2 9975.6 9452.1 7542.9 7517.5 7446.0 7404.9 7185.3 7179.5 7171.3  1.230 1.608 1.619 1.642 1.950 2.283 2.389 2.785 2.792 2.809 2.870 2.900 2.901 2.903 2.947 3.317 3.407 3.814 3.821 3.839  3.850 3.908 3.910 3.912  Config  5s8d 9p  Symbol  ID  3po  8d  3D  9p 10s 10s 9d 10p  lpo  9d 10p Us lis lOd lOd Hp 12s 12s lid  3s is  ID  3po  3  D  lpo  3s is  ID  3D lpo  3s !s  3-D m  J  2 0 1 2 1 2 3 1 1 0 2 0 1 2 2 1 1 0 2 2 1 1 0 2  Term Value (CM~1)  •U  3246.3 3224.3 3217.4 3198.6 3139.2 3138.5 3134.5 3103.1 2732.9 2665.7 2362.9 2331.5 2331.5 2331.5 2294.5 2276.2 2037.6 1995.6 1796.9 1751.3 1738.8 1576.8 1546.7 1419.3  5.814 5.834 5.840 5.857 5.912 5.913 5.917 5.947 6.337 6.416 6.815 6.861 6.861 6.861 6.916 6.943 7.339 7.416 7.815 7.916 7.944 8.342 8.432 8.793  TABLE Config  Symbol  j  Term Value (CM^l)  IIE  (Continued)  Config  Symbol  J  = |r2  Term Value (CM"1) • I  ?  Q  7P  4f 8s 8s 8p  7d  8p  lpO  3p° 3s  3 ->po s  ID  3po  7d 3D 8p 5f 9s 9s  lpO 2po 3 is  S  1. 2,3,4 1 0 0 2 1 2 1 2 3 1 2,3,4 1 0  7044.6 6957.1 5857.3 5634.1 4709.2 4701.7 4696.7 4663.6 4549.9 4546.3 4541.3 4483.4 4445.1 3856.6 3739.2  3.947 3.972 4.328 4.413 4.827  4.331 4.834 4.851 4.911 4.913 4.916 4.947 4.969 5.335 5.417  12p lid 13s 13s 12d 14s 14s 13d 13d 15s 15s 14d 14d  15d 15d I6d 17d 18d 19d  lpO 3  D  3D  3  S  is.  ID  3D  3  S  is ID  1  D  •4) 3D 3D 3D 3D  3D  1 2 1 0  2 1 0  2 2 1 0  2 2 2 2 2 2 2 2  1380.9  1379.3 1257.0 1239.$ 1114.3 1023.2 1010.8 942.5 920.3 849.2 846.4 782.7 771.6 669.6 658.1 566.7 492.1 430.6 383.1  8.915 8.920 9.343 9.408 9.924 10.356 10.419 10.790 10.920 11.368 11.386 11.841  11,926  12.802 12,913 13,916  14.933  15.964  16.925  THE ELECTRODELESS DS I CHARGE  To" MEGAVAC" PUMP  PLATE V  v  DISPERSION DE E l QUARTZ HILGER SPECTROGRAPH SO  "t  CC  *>UJ 1— U J  z: i  sect LU  .  Q _ OO  l ^~ o cc 1—  < 1 IO  — u VE-LE"NGTh (AUx Z0  I  i  i I  i  30,  40  SO  &P  "J  M O S E L E Y DIAGRAM FOR AG-' UKF ISOELECTRONIC SEQUENCE FIRST FORM OF I R R E G U L A R - D O U B L E T LAW  t & ] \ INDEPENDENT Of c An-0 J  PLATE VIII  J7  SO  4?  z  r  44  /  R E G U L A R - D O U B L E T LAW: LANDE DOUBLET FORMULA APPLIED TO AG-LIKE ISOELECTRONIC SEQUENCE.  1-7  8-CdZ  49  IUuF  i0Sn.lt>  ENERGY-LEVEL DIAGRAMS OF SOME SILVER-LIKE ATOMS. A g l (47)  Dk  5 P ' 2  <  "f  i  1 . *  a s  J  J-e  7  e  3  ft ••s  -81 -J  fii  (  6.  -  •  7  7,  —  p  4  i  \  S n ] ? (50)  z  >  p,I  1  i  l  i  -  1, . A  OO  -  7  CO  so 1-0  c Si  1  -*•  5  6  5  fa  35  J-C Z75  5.  #  n  j  k  ---  •-  S b Y (51) *<  5  6'.  5  s  Z-5  Mi HI  5  20 SO 700 5  IS  fa  WO  «.  est  134  MODIFIED MOSELEY DIAGRAM OF AN AG-LIKE ISOELECTRIC SEQUENCE  ELATE X I  ENERGY LEVEL DIAGRAM OF CADMU IM I '5 or)-  j-  'D  3  P  ~s  8 •'  7  f  J  0  9,  8J i fi  a ^  9* ! 6 7  2  3  23+  n'  A  &  '  z  7<  r  fc  : i  .5  6 20,000  D  3  5  c>  1  10,000  'P  ~  4-  0  u  40 SO  2-4  6l  20 Jo,ooo  40,000  5  —  --  /e  S0,000  60,000  70, OOO  5^  A  VI  BIBLIOGRAPHY  1. Albright, C.L., Phys. Rev., 3±, 847:  1930.  2. Bacher, R.F., and S.A.Goudsmit, Atomic Energy States, McGraw-Hill, 1932. 3. Badami, E., Proc.Phys. S o c ,  41, 538:  1931.  4. eg. Barss, W., Thesis, The Spectra o f Iodine, (The University o f B r i t i s h Columbia, A p r i l , 1939. 5. Bethe, H., Rev.Mod.Phys., 8, 206-226: 6. Bioch, L. and E., Ann. de Phys., 5_,  1936.  325:  7. Bohr, N., Phil.Mag., 26, 1, 476, 857: 8. B r e i t , G., Phys.Rev., 3J, 9. 10.  51:  1913.  1931.  —  , see Goudsmit, S.A., Phys.Rev.42,  —  , and L.A.Wills, Phys.Rev. 4Jt»  11. Casimir, H.B.G., Physic*, 2,  719:  12. Crawford, M.F., Phys. Rev. /£, 13. 14.  1936.  768:  636:  470: 1933.  1935. 1935.  and L.A.Wills, Phys. Rev., 48, Darwin. C.G.. P r o c R o y . S o c . A 116 .  227:  69:  281: 1926.  16.  °l-  P r o c R o y . S o c , A 112,  17. Esclangan, F., Jour.de Phys. et radium,  0:  1935.  1927.  15. Dirac, P.A.M., P r o c R o y . S o c , A 111. _  1933.  1  927.  Z> 52:  1926.  18. Fermi, E., Z e i t s , f.Phys., 60, 320: 1930. 19. Fowler, A., Report on Series i n Line Spectra, Fleetway Press, 1922. 20. Fues, E., Ann.d.Phys., 6£, 1: 1920. 21. Gibbs, R.C., Rev. Mod.Phys., Jt, 278, 1932. 22.  —  and H.E.White, Phys. Rev., 31, 776:  1928.  BIBLIOGRAPHY 4JJ,  23. Gordon, W., Zeits.f.Phys. 24. Goudsmit, S.A.,  Phys.Rev.,  25. Green, M., Phys.Rev.,  27. Jones, E.G.,  11:  3_7_,  3.,  1929.  663:  117:  60,  26. Hertz, G., Z e i t s . f .Phys.  (Continued)  1931.  1941.  19:  1920,  Proc.Phys.Soc, 4J>,  625:  1933.  28. Lande, A., Z e i t s . f .Phys.,  1£,  189:  1923.  29.  2j>,  46:  1924.  —  Z e i t s . f . Phys.,  30. Lang, R.J., Proc.Nat.Acad.Sci., 31. Mazumder, K.C,  15_,  414:  1929.  Ind.Jour.Phys., 17.,  229:  1943.  32. M i l l i k a n , R.A., and I.S.Bowen, Phys.Rev., 2^,  209:  1924.  33. McLennan, J.C., A.B.McLay, and M.F.Crawford, Trans.Roy. . Soc. Can., 22, 45: 1928. 34. Paschen, F., —  35.  Ann.d. Phys., Ann.d.Phys.  20,  2£,  36. P a u l i , W.,  Naturwissenschaften,  37.  Zeits.f.Phys.,  —  40. Ruark, A.E.,  860:  41,  38. Pauling, L., and S.A.Goudsmit, Spectra, McGraw-Hill, 1930. 39. Racah, G., Zeits.f.Phys.,  746:  1909. 1911.  12,  741:  601:  1927.  1924.  The Structure of• Line  71.,  Jour.0pt.Soc.Am.,  41. R u s s e l l , H.N., and F.A.Saunders,  431:  1931.  11,  199:  1925.  Astrophye.Jour.,  . 61, 38: 1925. 4 2 . von S a i l s , G., Ann.d.Jhys.,  76.,  145:  1925.  43. Sawyer, R.A., Experimental Spectroscopy, Prantice-Hall, 1944. 44. Schuler, H., and H.Brfick, 45.  ~  Zeits.f.Phys.,  56,  and J.E.Keyston, Zeits.f.Phys., 71,  291: 413:  1929. 1931.  BIBLIOGRAPHY  (Continued)  46. Schuler, H., and H.Westmeyer, Zeits.f.Phys. 82, 47. Sigittra, Y.,  48. Sommerfeld, A., 49.  Ann.d.Phys., 51>  155: 1  :  42:  Ann.d.Phys.,  Turner, L.A., Phil.Mag.,  48.,  384*.  1933.  1924. 1916.  and W.Heisenberg, Zeits.f.Phys., 11,  —  50. Takahashi, Y., 51.  3_,  Jap.Jour.Phys.,  685:  131:  1922.  1929. 1924.  52. Uhlenbeek, G.E., and S.A.Goudsmit, Naturwissenschaften,  23_,  953:  ,1925.  53. Unsold, A., 54. White, H.E.,  .  Zeits.f.Phys.,  3±,  92:  1926.  Introduction to Atomic Spectra, McGraw-Hill,  1934.  

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