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Studies in the spectra of iodine and the problem of filling a spectrograph Newton, Theodore Duddell 1941

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STUDIES IN THE SPECTRA. OF IODINE and THE PROBLEM OF FILLING- A SPECTROGRAPH  by-  Theodore Duddell Newton  A Thesis Submitted for the Degree of MASTER OF ARTS 7  in the Department of PHYSICS  The University of B r i t i s h Columbia A p r i l , 1941  TABLE OF CONTENTS  Page Studies i n the Spectra of Iodine 1. Introduction  1  2. Experimental a. The spectrographs b. The electrodeless discharge.. c. The Schuler tube d. The Schuler tube vacuum system.... Photograph of Schuler tube vacuum system, facing... e. The Schuler tube power source Photograph of Schuler tube apparatus, facing  10  3. Compilation of Data.  10  2 3 5 7 7 8  4. Results f  a. b. c. d.  Excitation data. Arc lines.... Grating plates Wavelengths from 2496.07 to 2061.59 A.... 5. Bibliography The Problem of F i l l i n g a Spectrograph Acknowledgement  12 12 12 13 19 20  STUDIES IN THE SPECTRA OF IODINE  1.  Introduction: Our knowledge of the atomic spectra of iodine i s comparatively  limited.  Indeed this whole section of the periodic table has been studied  but l i t t l e u n t i l recent years, though considerable progress has been made lately. The d i f f i c u l t i e s l i e , not i n the excitation of iodine, but i n the extreme complexity of the spectra produced.  In the radiation emitted  by the electrodeless discharge, for example, more than 2000 lines of wavelengths between 6960 A. and 2060 A. have been observed i n the present investigation, and these are a mixture of I, , I„ , I,„  , and I„ , with I„  predominating. Previous to 1930 wavelength measurements were made by Kerris"*" 2  (7468 A. to 2562 A.) and by L. and E. Bloch (6580 A. to 2220 A.)' Since 3 then some lines have been measured i n the fa*r ultra-violet by LaCroute (2258 A. to 766 A.) and others.  In his memoir, LaCroute also gives Zee-  man effect data on many of the strong I„  lines, and makes"an analysis of .  5 classifying 130 lines arising from 54 terms. spectrum, Evans published a l i s t of arc lines and an analysis of the I, spectrum.  the I  l(  1. Eerris, W.;  Zeits. fflr Phys.  60, 20, (1930).  2. Bloch, L. andE.; Ann. de Phys. 11, 141 (1939). Bloch, L. and S.; Ann. de Phys. 16,503 (1931) - a correction. 3. LaCroute, P; Ann. de Phys. 3, 1, (1935). 4. Turner, L.A., and Millikan, S»; Phys. Rev. 27, 397, (1936). McLeod, J.H.j Phys, Rev. 49, 804, (1936). 5. Evans, S.F.;  Proc. Roy. Soc.  A 133, 417, (1931).  - 2The most nearly complete work has been done by Murakawa who has written a series of papers on iodine and related spectra. In 1938 he pub6 lished an analysis  of I, and I„ based mainly on the wavelength measure-  ments of L. and E. Bioch, i n which he classifies 50 lines arising from 30 terms of I, and 300 lines arising from 82 terms of I„ ... The analyses of I, by Ivans and Murakawa are i n only p a r t i a l < agreement, while those of I„ by LaCroute and Murakawa are i n good agreement. No analysis of any meaning has been made on I„, or I, -. v  Mention must be made, however,to&the very comprehensive analyses of related spectra that have been made i n the last few years at 7  8  the U.S. Bureau of Standards. Analyses of Ze„ and Xe„  t  by Humphreys  w i l l be of great assistance to future investigators of iodine spectra. 9 P a r t i a l analyses of Sb, by Rao and Sastry and of Te, by ' B a r t e l t ^ are also available. • 2. Experimental: a) The spectrographs; During the present investigation spectrograms from an electrodeless discharge and from a Schiller tube have been obtained over the wavelength region 6960 A....to. 2060 A. Plates from both types of discharge were obtained on a Hilger E l quartz l i t t r o w spectrograph. This instrument 6. Murakawa, K.; Zeits. fur Phys.  109, 162 (1938).  7. Humphreys, C.J.; Bur. of St., Jour. Res., 22, 19, (1959). 8. Humphreys, C.J.; Bur. of St., Jour. Res., 16, 639, (1936). 9. Rao and Sastry; Nature, Rao and Sastry; Nature,  146, 523, (1940). 143, 576, (1939).  10. Bartelt, 0.; Zeits fur Phys.  88, 522, (1934).  - 3may be used from the visible red to the limit of a i r transparency. Three different settings, each extending over a 10-inch photographic plate give 6960 A. to 3270 A; 3390 A. to 2420 A; and 2490 A. to 2050 A. Spectrograms from the Schuler tube were also made on a medium quartz Hilger E498 spectrograph i n order to obtain this entire spectrum on one plate. A spectrogram was made on the 6-foot concave grating, using a Rowland mount. The region photographed contained nX values from 10,920 to 8,720, approximately, and gave here a dispersion of about 9.25 nA per mm. Photographic plates used were,for 6960 A. to 2420 A.  - Ilford Hypersensitive Panchromatic;Eastman I I F.  for 2490 A. to 2000 A.  - Ilford Q, 1,  The latter plates were found to be of especial value on account of their fine grain and speed i n even t h i s extreme ultra-violet region. b) The electrodeless discharge;  liov. B.C.  i  niimnrii  To  Meqavac  In the electrical circuit shown, the 6 kva transformer produced a secondary voltage rising to 100 kv.  Included i n the primary was a heavy  duty control resistance, variable i n steps from 5 to 12 ohms. Primary currents used varied from 10 to 30 amperes. In the secondary circuit the condenser shown consisted of 6 Leyden jars, arranged i n two banks i n series, each bank being three jars i n p a r a l l e l .  The capacity of this combination  i s approximately .0025 m.f,d. The spark gap consisted of two iron hemispheres, 8 cm. i n diameter and the gap used varied between 1 and 2 cm.: the induction c o i l of 17 turns of #12 bare copper wire was 2.3 cm. i n diameter, 9 cm. long, and was separated from the discharge tube by a thin mica core. The tube i t s e l f was of Pyrex glass with quartz windows waxed on each end.  This was found quite satisfactory since the ends of the tube did  not become hot with even the highest excitation used. The induction c o i l was kept cool by a jet of compressed a i r , or by the action of an electric fan.  The glass tubing lead to the Genco Megavac vacuum pump led through  a trap kept immersed i n an ice-water mixture. In operation, resublimed iodine i n flakes was placed i n the discharge tube and the system evacuated.  Three stages of excitation were pro-  duced, 1) high excitation, using a primary current of 25 amperes, the lowest pressure obtainable, and a spark gap of 2 cm. 2) medium excitation, cutting off pump and allowing the iodine vapor pressure to build up, but maintaining the same primary current and spark gap. 3) low excitation, with pump s t i l l cut off, and using a primary current of 15 amperes, and a spark gap of 1 cm.  Excitation conditions within the tube were checked visually using a hand spectroscope. • • Several sets of plates i n each of the three regions available to the Hilger E l were obtained.  On each plate the high excitation was f i r s t  exposed, then using a shorter s l i t a comparison spectrum of iron arc (or copper i n the region 2490 A. to 2000 A.) was superposed by passing the light from the arc down the tube. Quartz windows were used on both ends for t h i s purpose. The lower excitation spectra from the electrodeless discharge were then placed on the plate i n adjacent positions. With the Rowland grating only the high excitation was used, since wavelength measurements, not excitation data were required. In this case the iodine tube was removed before adding the copper comparison spectrum. No Hartmann diaphragm could be used on this s l i t because of the astigmatic image formed by the grating. However, since the iodine was excited over an extended region, close to the s l i t , and the copper was excited i n an arc of a few millimeters length at some distance from the s l i t , the two sets of spectral lines were of entirely different lengths on the plate and could be easily distinguished. c) The Schttler tube; This method of exciting spectra i s described i n a series of papers by Paschen and Schuler.  1  One paper"*""" i n particular discusses the  source very f u l l y , giving details of best construction as worked out by Schuler.  11. Schuler, H.; Zeits. fur Phys.  35, 323  (1926).  c  The type of tube used consisted of a hollow steel cathode A with a brass water jacket, inlet B outlet C; these were turned by Mr. W. Eraser i n the machine shop of the Physics Department.  Inserted i n the open end of  the cathode was a Pyrex glass tube D. This was provided with three inlets, E, E, G-, & and E connected with the gas circulating system to be described later, while E was covered with a brass cap through which a brass rod connected with an inner brass cylinder H. The discharge occurred from H to A. A quartz window E was waxed on the end of the glass tube; a l l the metal-glass seals were also made with wax, which proved perfectly satisfactory, f o r the water flow through B 0 kept the tube cool even when used with the maximum available power.  d) The Schuler tube vacuum System  Connections to Schiller tube  The purpose of t h i s system was to keep a constant concentration of iodine vapor i n the Sehtiler tube. Argon from the l i t r e bulb A at a pressure of about 2 mm. of'mercury (indicated by the manometer B) was used as a carrier.  Traps 0, D, I , IT, were cooled by solid carbon dioxide i n  Dewar flasks, while traps G- and H contained metallic calcium and copper oxide respectively. Resublimed iodine i n flakes was placed inside the Sehtiler tube. The entire system was constructed of glass tubing save only the connections with the discharge tube i t s e l f , which were rubber so that the tube might be movable. Before operating the system, i t was evacuated and argon introduced through the stop-cock K into the bulb A to a pressure of about 50cm. of mercury. This proved more than sufficient for the entire period of use of the system, which therefore did not need to be opened to the a i r beyond the stop-cock L.  In operation, the system was f i r s t evacuated by closing the stopcock M and using the Megavac and mercury diffusion pump i n series.  Then L  was closed, M opened, and argon introduced from A to a pressure of 2 mm. of mercury.  The diffusion pump kept the gas circulating, and i t was purified  by heating traps G and H.  The cold traps prevented the entry of iodine or  mercury vapor into the rest of the system, and removed water vapor formed in the removal of hydrogen by the hot copper oxide. The cathode was then wrapped i n solid carbon dioxide, power supplied to the tube, and the spectrograms exposed. A comparison spectrum was superposed through a short s l i t by swinging the Schuler tube up from in front of the s l i t . e) The power source for the Schuler tube.  Pole t r a n s f o r m e r  i—rmnnnnnrv-. , fl.C.IIOV.  II XL f  Out  put.  The power source shown above used a bridge circuit of four 866 diodes to provide f u l l wave rectification of the complete secondary voltage of the 2 kva pole transformer.  The f i l t e r circuit contained inductances of  30 and 10 henries and two condensers of 2 mfd capacity each. A leak resists ance of 100,000 ohms was used. For purposes of control a resistance variable up to 11 ohms was placed i n the primary of the pole transformer, and a ballast resistance variable up to 8920 ohms was placed i n the output i n series with the SehQler tube.  The filaments of the rectifying tubes were heated by transformers  (only the secondaries are shown) connected i n p a r a l l e l with the primary of the pole transformer.. This power source was constructed by Mr.  Retallack.  The output voltage of the source was about 2000 volts, and was very steady f o r currents up to 250 milliamperes. was used on the tubes.  Only a fraction of this  With the ballast resistance f u l l ,in, from 100 m i l l i -  amperes at 425 volts to 150 milliamperes at 450 volts were supplied to the tube.  With 3100 ohms ballast the power input at the tube varied from 150  milliamperes, 450 volts to 300 milliamperes, 125 volts; these variations being obtained by use of the rheostat i n the primary.  The tube was found  to run most satisfactorily at 100 milliamperes, 425 volts, but plates were taken With a variety of currents to observe the effeet, i f any on the spectra produced. It i s interesting to compare the current voltage relation found ' 12 in this investigation with the results obtained by Rose and Granath. In the investigation of the spectrum of lead, excited i n a  12. Rose and Granath; Phys. Rev. 40, 760, (1932).  •Schtller tube i n an .atmosphere'-of helium, these investigators used a direct current motor, generator as a power source.  They found that as the voltage  at the terminals of the generator was iricreased, the voltage across the tube remained, at f i r s t , nearly constant while the current increased (from .2 amperes at 180 volts to .8 amperes at 210 volts).  Then as the generator  voltage was s t i l l further increased, the voltage across the tube rapidly increased and the current decreased (from .8 amperes at 210 volts to .3 amperes at 700 volts.) In the f i r s t type of excitation the tube remained cool, while i n the l a t t e r type the iron cathode could be made red hot. In the present investigation a l l the currents used would f a l l into the f i r s t stage of: Rose's experiment. But the behavior of the tube was quite different, at least for currents greater than 150 milliamperes. This difference could be due to the different gases used, and to some d i f ferences i n construction of the tube. An enlarged photograph of the Schiller tube apparatus showing the power source, vacuum system, and the s l i t of the Hilger 11 spectrograph, accompanies this report. 3.  Compilation of Data: The existing analyses of iodine and related spectra have been  assembled i n a form convenient for ah attack on the problems of extending , the analyses of I, and I„  and starting the analyses of I,„  and I  w  .  "To this end quadratic arrays of the terms of Sb, , Te„ ; Te, , I„ , Xe,,, ; I, , Xe„ ; have been made, and Moseley curves for the deepest lying terms of the isoelectronic sequence Te, , I„ , Xe,,, , have been drawn.  ';  These papers, representing a considerable amount of work, have been turned over to Dr. A. M. Crooker, who hopes that t h i s project may be  - 11 carried forward. !  The Moseley diagrams 'brought to light an interesting discrepancy in the published papers. The term value for an ion i n a ejigen electronic configuration may 2 - 1 be written i n the form T = R Z cm. where R i s the Rydberg constant fo'r the atom Z i s i t s atomic number n*  i s the effective value of the total quantum number for the given electronic configuration.  This formula i s made to follow the form of the original simple Bohr theory. Now i n an isoelectronic sequence of large atomic numbers, n* w i l l be practically constant for the same configuration i n each of the ions of the sequence. p Hence the value of T/R w i l l vary as Z . A Moseley curve i s a graph of •/T/R against Z, for the same electronic configuration through an isoelectronic sequence. Such a graph i s practically a straight line, but usually has a slight concavity toward the Z axis. In plotting the values f o r the deepest lying terms of Te, as given by Bartelt, of I,, as given by Murakawa, and of Xe,„ as given by Humphreys, the curves displayed a slight convexity to the Z axis. Now a l l of Murakawa's terms had been lowered by an amount 2720 -1 cm.  over those given by LaCroute.  When LaCroute's values were put i n  place of Murakawa's, the Moseley curves took the correct form. It was therefore concluded that the absolute values of the terms of Murakawa's more extensive analysis should be increased by the above amount of 2720 cm.  -1  - 12 4.  Result s:  a) Excitation data. The excitation plates obtained from the electrodeless discharge were examined carefully i n comparison with the tables published by L. and E. Bloeh, and those tables were, i n general, verified.  This examination  covered the region 6900 A. to 2500 A. b)  Arc Lines. The plates obtained from the Schuler tube were also carefully  examined. It was found that certain of the I,, lines appeared on these plates, though the majority of the lines were I , . The non-existence of arc lines i n the region from 2061 A. to 3400 A. was. confirmed. Evans' l i s t of arc lines stops at 4763 A. at the short wave-length end.  It could not  be decided whether any arc lines occurred between 4763 A. and 3400 A. but i t seemed l i k e l y . A large number of molecular bands also appeared on the Schuler plates of which four occurring approximately at 3250 A., 3260 A., 5212 A. and 3188 A., were most peculiar.  These were not bands, so much as extreme-  l y broad lines, almost continua, 10 to 15 Angstroms i n width. c) G-rating Plates. A plate showing the spectrum of the electrodeless discharge in the nA region 10980 to 8720 was taken on the Rowland grating by Mr. W. M., Barss. This was measured i n the hope of establishing exact wavelengths of some of the stronger wavelengths i n the visible and near ultraviolet. However a l l the lines appearing on the plate had been previously measured by Kerris on a 21 foot grating, so t h i s work added nothing new. In the present investigation a similar spectrogram was obtained  - 13 on an Ilford Ql plate which i s sensitive as low as 2000A. This was done to establish the' wavelength of the very strong arc line at 2061 A. Turner and Millikan had measured, this l i n e , at 2062.25 A. with three others 1876.40 A., 1844.39 A., and 1830.32 A. in vacuum.  LaCroute  had- i n his tables, given these lines the wavelengths 2062.38 A., 1876.56 A., 1844.56 A., 1830.49 A., i n vacuum. Thus LaCroute*s entire l i s t of lines was displaced .13 to .17 A. from Turner's values. To measure the three shortest wavelengths requires a vacuum spectrograph, but the l i n e at 2061 A. could be obtained i n a i r . It was obtained on the Rowland grating, and fortunately occurred, in the f i f t h order spectrum, i n the midst of a group of strong lines, 2564.401 A., 2566.258 A., 2582.808 A., 2593.466 A. which occurred i n the fourth order, and 3424.971 A. i n the third order whose wavelengths had been determined by Kerris with great precision.  I t was thus possible to measure  the l i n e very exactly and the value 2061.59 A. i n a i r obtained. This i s in complete agreement with Turner, and points strongly to the assumption that LaGroutds values are i n considerable error i n this-region.  This  assumption i s further supported by other measurements discussed below, d) Wavelengths from 2496.07 to 2061.59 A. Plates from the Hilger B 1 spectrograph covering this region have been measured. The dispersion on these plates varies from 2.5 A./mm. to 1.5 A./mm., so that precise measurements are possible. In the l i s t s which appear below a l l excitation and intensity assignments have been made from the plates of this investigation, and i n general the excitation data agrees with that of Bloch and Bloch, and of LaCroute, where these l i s t s coincide.  - 14 Wavelengths for a l l lines on the plate were calculated by Hartmann formulas, arid then between 2496.07 A. and 2230.56 A* inclusive, were corrected to the values given by L. and E. Bloch. Lines not given i n their l i s t are marked "new". Lines classified by Murakawa i n the I„ spectrum are marked 'M". These corrections established the fact that there was no displacement between the copper comparison spectrum and the iodine, so that the copper lines were used to correct the wavelengths given by the Hartmann formula i n the region 2229.19 to 2061.59 A. inclusive.  These lines, then,  are entirely new measurements, which should be accurate to within  .02 A,  Lines which have been measured by LaCroute i n this region are marked with an L but his measurements are often i n considerable disagreement with the new values here given. Bloch and Bloch do not extend their l i s t into this region.  Int. 3 3 8d 2 3 7d 1" 3 5 3 1 1 1 6 . 00 0 0 3 3d 1 2 0 0 3 1 0 0 1  air  2496.07 95.16 94.71 93.21 92.50 91.61^ 90.40 89.76 89.27 88.99 87.00 86.10 85.23 84.64 84.12 83.40 83.03 82,05 81.09 80.00 79.75 79.43 78.95 78.04 77.64 76.78 76.21 75.73 75,36 4 73.25 1 00 72.84 1 71.53 3 71.21 3 71.01 '1 70.54 1 69.81 2d 69.21 0 67.92 00 67.11 'l' 66.99 2 66.69 3 . 64.95 lOd . 64.67 3 63.98 2 63.30 2 62.50 8 61.10 2 60.43 . 2 60.01 00 59.37  vac. Exc. Remarks Int. 40050.9 65.5 72.7 97.8 40108.3 22.6 42.1 52.4 60.3 64,8 97.0 40211.5 25.6 35.1 43.6 55.2 61.2 77.1 92.7 40310.4 14.5 19.7 27.5 42.3 48.8 62.8 72.1 79.9 86.0 40420.4' 27;.i 48.5 53.8 57.1 64.7 76.7 86.5 40507.7 21.0 23.0 27.9 56.5 61.1 72.5 83.7 96.9 40619.9 31.0 37.9 48.5  Ill III II IV III II III  00 2 00 4 2 4 1 1 4 0, 3 4 3 1  II  17 II III IV IV III III TV It III III II II III .IV III IV IV IV III • IV III III III II III III III III III III IV III III II II HI rv II II in  6  new new  1 1 1 1 4 1 4 4  1 new  3 2 0 3 2  4 ' new  M  M new new  1 3 3 3 ~4 5 .1 1 1 0 2 00 0 4 2 6 2 2 2 "1  air  vac. Exc. Remarks  2458.94 40655.6 58.18 68.2 57.63 77.3 57.27 83.2 56.58 94.7 54.46 40729.8 53.97 38.0 51.08 86.0 50.36 98.0 48.69 40825,8 48.48 29.5 47.89 40.5 47.47 46.1 46.49 62.5 44,12 40902.1 41.83 40.5 41.43 47.2 39.43 80.8 39.23 84.1 38.28 41000.1 37.88 06.8 37,61 11.3 36.20 35.1 35,87 40.6 34.88 57.5 33.99 72.3 32.93 ,90.2 30.92 41124.2 29.49 48.4 26.12 41205.6 23.91 -43.1 23.40 51.8 23.21 55,0 22 o 32 70.2 19.41 41319.8 19.16 24.1 18.49 35 ® 5 17.81 47.2 15.62 84.6 15.08 93.9 14.85 97.8 14.47 41404.4 13.34 23.7 12.52 37.8 11.95 47.6 07.98 41515.9 07.57 22.8 06.45 42.3 05.91 51.7 05.34 61;5  new II  new niIV n II HI in  new II in II in II II II IV IV II ' II in in in in in  M new  M  new in  17. 17 17 III IV III III n II II III  new 17 III  new II III II III III III III  new  Int.  air  1 2404.88 .3 04.03 3 03.63 3 03.06 0. 02.68 0 02.31 1 01.32 1 2400. 56 2 2400.10 1 2399.24 3 98.15 1 97.69 3 97.21 0 96.63 'o 95.74 3 95.20 2 94.94 2 94.42 3 92.92 4 92.35 3 92.01 87.12 3 1 85.28 5 84.03 1 82.35 2 81.79 2 80.99 1 80.71 1 79.42 1 78.00 4 77.09 4 76.47 0 74.54 3d 72.45 3 72.23 2 71.45 1 69.96 2 69.55 0 69.07 1 68.36 3 67.74 0 65.28 Od 63.02 00 62.59 Id 62.44 3 61.35 3 61.15 Od 60.53 3 60.13 2 59.69  vac. 33xc. Remarl 41569.5 84.2 91.1 41600.9 07.5 13.9 31,1 44.3 ^ ' 52.2 65.1 87.9 94.1 41702.5 12.5 28,0 37 i 4 • 42.0 51.0 77.2 82.2 93.1 41878.7 41911.0 33.0 62.6 72.4 86.5 91.5 42014.2 39.3 55.4 66.4 42100.6 37.6 41.6 55.4 81.9 89*2 97.8 42210.4 21.5 65,4 42305.8 13.7 16.2 35.7 39.3 50.4 57.6 65.5  Ill  new  n  17 IT ni  new in in ni ii II HI II  new  new ill.: •II'IT IT  17 III 17 IT 17 II III III III III II II III  new  IT  III IT  II 17 III II III II 17 II  New  II  new new  III III  new  n in in  17 in  new  Int. 1 0 2 3 2 1 1 0 2 1 0 1 5 1 1 5 5 2 2d 7d 0 2 1 1 1 0 1 7d 4 0 2 5 Od 0 0 0 0 4 3 00 1 3 0 2 2d 0 5 1 1 '2  air 2359.25 58.73 57.54 54.35 53.46 52.93 50.80 50.19 48.56 48.03 47.49 47.10 46.32 45.68 45.37 44.58 44.36 43.85 43.40 42.38 41.57 40.85 40.29 39.71 39.33 38,38 36.18 35.45 34.13 33.71 32.99 31.54 30.36 29.47 29.26 29.10 28.92 28.40 27.29 26.11 25.60 24.70 24.27 22.94 22.45 21.60 20.20 19.86 19.04 17.44  vac. Exc. Remarl 42373.4 17 82.7 III 42400.5 II 61.6 II 77.6 n i 87.2 n 42525.7 IT 46.7 i i . 66.2 n 75.8 H I 85.6 i n 92.7 i n 42606.9 i i 18.5 i n 24.1 I I 38.5 i n 42.5 i n • 51.8 i n 60.0 i n 78.5 n 93.3 i n 42706.4 i n 16.6 i n 27.2 17 34.2 17. 51.5 I l l 91.8 III 42805.2 II 29.4 I I 37.1 III 50.3 II 76.9 II 98.6 II 42914.0 III 18.9 III 23.7 III 25.2 III 34.7 III 55.2 III 77.0 III 86.4 III 43003.1 n i 11.0 i n 35.7 i n 44.7 i i 60.5 I I 86.5 I I 92.8 n 43108.0 n 56.4 i n  new new new new  new new  M new M new new new new new new  new new new  - 17 Int. 1 1 0 2 2 00 Id 1 3 6 2 5 Od 0 Od 3 1 2 o'  7 6 6 7 0 0 5 6 2 3 1 1 1 1 1 2 1 2 2d 2 2d 1 1 8 3 1 0 -•2d 0  "6  air' 2317.13 16.83 15.92 15.51 14.88 12,92 10.98 10.45 09.38 08.57 07.93 07.68 05.84 04.58 02.96 00.84 2300.43 2297.43 96.07 94.12 93.68 93.24 92.64 92.44 91,98 91.79 88.68 87.89 86.53 84.90 84.18 83.41 •82.56 81.90 80.76 80.05 78.53 76.24 74.26 69.21 67.91 66.72 66.41 65.69 63.82 63.62 62.91 61.93 61.35 60.01  vac. Exc. Remari 43143.6 49.1 66.1 73.7 85.5 43222.1 57.4 68.3 88.3 43303.5 15.5 20.2 54.8 78.5 45409.0 49.0 56.7 43513.5 39.2 76.2 84.6 93.0 43604.408.2 16.9 20.5 79.8 94.9 43720.9 52.1 65.8 80.6 96.9 43809.6 31.5 45 -il 74.4 43918.556.7 44054.6 79.8 44102.9 09.0. 23.0 59.4 63.3 77.2 96.3 44207.7 33.9  Ill III III II III III II  new new  n  17 in n n II II II  in ii n ii II  new new new new new new  in II-  in in in Hi II II II II  i n HI II II  in  17 III ;II III III III III III III III III III II III II  new new M new M new new new new= new new new  hew new new new  Int. 3 3 Od 0 1 1 1 1 8 0 1 1 2 00 0 0 4d 4 1 Od 0 1 0 2d  air 2257.61 56.68 55.21 54.56 54.22 52.95 51.83 51.11 49.31 46,70 44.67 44.25 41.40 40.51 40.06 39.71 39.37 38.12 37.20 36.67 35.28 32.32 31.30 2230.56  vac. Exc. Remarks 44280.9 I I I new 99.1 I I new 44328.0 n new 40.8 I I new 47.5 I I I ' • new 72.5 I I new 94.5 n new 44408,7 H I new 44.3 I? 95.9 .i n new 44536.1. I I new 44.5 i n new 44601.1 i n new 18.8 i n new 27.8 i n new 34.7 i n new 41.5 n 66.5 i n . 84.8 i n new 95.4 n new 44723,2 n new 82.5 i n new 44803.0 i n new 44817.8 I I new  8 \ 2229,19 44847.4 I I 00 27.34 82.6 I I 1 25.71 44915.5 H I in 4 24.53 4 23.80 54.0 i n 0 22.78 74.7 i n 0 21.90 92.5 i n 3 19.86 45023.8 i n 1 19.47 41.7 i n 1 19.24 46.4. i n 2 17.26 66.3 I I 1 16.40 45104.1 i n 2 14.46 43.6. i n 4 . 13.30 67.3 i n b 11.49 45204.3 n l 11.11 12.0 I I Id 10.33 28.0 I I Od 08.82 58.9 n 0 07.77 80.4 n 0 06.75 45301.3 i n 5 03.38 70.6 i n 0 2200.49 45430.2 n 1 2198.16 78.4 n 0 96.96 45503.2 n  L L L L L L  L L  - 18 Int. 2 Od 2 2 2 0 I 5" 0 6 2 2d 2 3 0 0 0 0 4 1 5 5 1 1 0 Od 0 00 00 0 2 '2 2  air 2196,68 94.55 92.51 92.23 90.29 88.00 87.62 84.89 84.36 82.48 81.29 79.35 77.35 77.19 76.91 75.59 73.21 72.52 72.19 71.85 69.09 68.74 66.36 65.10 64.50 64.05 62.60 61.34 61.12 60.28 58.01 52.14 51.38  vac. Exc. Remarks Int. 45509.0 53.1 93.-5 45601.4' 41.7 89.5 97.4 45754,4 65.6 45805.0 30.0 70.8 45913.0 16.3 22.2 50.1 46000.4 15.0 22.0 29.2 87.8 95.2 46145.8 72.7 85.5 95.1 46226.1 53.0 57.7 75.7 46324.4 46450.7 67.1  :, i i II  in ii in in in in in in in in  L  L L  n  in in in. n in . II  L  in in in ill in in . II ,  in in in III : III III III  L L L  air  4 2150.13 48.73 o 2 47.22 1 41.30 1 41.00 2 35.85 2 33.76 2 30.36 0 27.52 1 25.84 2 25.26 4 22.07 2 19.86 b 18.70 .l 17.01 2d 14.76 3 09.67 0 07.30 I 06.96 3 06.03 1 05.12 o04.42 0 2104.23 b 2099.22 3 96.78 3 93.75 0 92.39 2. - 91.30 '5 86.83 3 80.58 0 74.77 0 68.46 20 2061.59  vac. Exc. Remarks 46494.1 46524.4 57.1 46685.8 92.4 46804.9 50.8 46926.4 88.2 47025.3 38.1 47108.9 58.0 83.8 47221.4 71.7 47385.7 47439.0 46.6 67.6 88.1 47503.9 08.2 47621.6 77.0 47746.0 77.0 47801.9 47904.3 48048.1 48182.7 48329,6 48490.7  II III III n  L L L  II  in in in n in  L L L  HI  n n  L L  II  n ' n in in in in n in II  n ii in in u  in in in in i,  L L . L L L L L L L L L L L L L L  - 19 BIBLIOGRAPHY Angenetter, II. "Zeeman Effect i n Xe„ Spectrum" Zeitschrift fur Physik, 114, 636 (1939) Barss, W. M. "Spectra of Iodine" A thesis for degree of Master of Arts, University of B r i t i s h Columbia, (1939) Bartelt, 0. "Arc Spectrum of Tellurium" Zeitschrift fur Physik, 88, 522 (1934) Bloch, L. and C. "Spark Spectra of Iodine" Annales de Physique, 11, 141 (1929) and Annales de Physique, 16, 503 (1931) Deb, S. G. "On the Arc Spectrum of Iodine" Proceedings of the Royal Society of London A 139, 380 (1933) Evans, S, F. "The Are Spectrum of Iodine" Proceedings of the Royal Society of London A 133, 417 (1931) Humphreys, J . C. "Second Spectrum of Xenon" Journal of Research of the National Bureau of Standards, 22, 19 (1939) and  "Third Spectrum of Xenon" Journal of Research of the National Bureau of Standards, 16, 639 (1936) 1  Humphreys, J.C.; Meggers, W.I..; LeBruin, T.L. "Zeeman Effect i n Xe„ and Xe,„ Spectra" Journal of Research of the National Bureau of Standards, 23, 683, (1939) "Tabelle der Saaee^ungszanlen" Published i n Leipzig, 1925. _ Kerris, W. "Measurements i n the Spark Spectra of Iodine" Zeitschrift fur Physik, 60, 20, (1930)  Krishnamurty, S. G. "Regularities i n the Spectrum of Trebly Ionized Iodine" ' ; Proceedings of the Physical Society, 48, 277 (1936) . LaCroute, P. "Zeeman Effect i n Bromine and Iodine" Annales de Physique, 3, 1, (1935) . McLennan, J . G.; and McLay, A. B. "Structure of the Arc Spectra of the Elements of the Nitrogen Group" Transactions of the Royal Society of Canada, XXI, Sect. I l l , 63 (1927) McLeod, J . H. "Lines i n the Ultraviolet Spectrum of Iodine" Physical Review, 49, 804, (1936) M.I.T. Wavelength Tables Published by the Massachusetts Institute of Technology, 1939. Murakawa, K. "On the Spectra of I„ , 1 , and Cl„ " Zeitschrift fur Physik, .109, 162, (1938) Rao and Sastry and  "Spectrum of Te„ " Nature, 146, 523 (1940) Nature, 143, 376 (1939)  Robertson, J . K. "The Electrodeless Discharge i n Certain Vapors" Physical Review, 19, 470 (1922) Rose, J". L. and Granath "Fine Structure i n Pb„ " Physical Review, 40, 760 (1932) Schuler, H. "A New Light Source" Zeitschrift fur Physik, 35, 323 (1926) Shenstone, A, G. "Atomic Spectra" Reports on Progress i n Physics, of the Physical Society, London; Vol. V, 1938 Turner, L. A., and Millikan, G. "Arc Lines of Iodine i n the Schumann Region" Physical Review, 27, 397 (1926)  THE PROBLEM OF FILLING A SPEQTRO GRAPH The problem of f i l l i n g a spectrograph with light from a spatially extended source has been considered by Nielson^ from the standpoint of geometric optics, i.e. neglecting diffraction at the s l i t .  He has assumed  an indefinitely narrow s l i t . It became of interest to determine how his results would be modif i e d by considering a s l i t of f i n i t e width. This correction seemed of possible importance since theslit length, i n work with Raman spectra, i s often related to the s l i t width by a factor of as low as ten. The problem i s , then, to determine the amount of light that w i l l enter a collimating lens of focal length t_ masked by a diaphragm of width 2a and height 2b, these chosen to coincide with the aperture of the prism, and so to simplify the problem. The s l i t i s taken 2s long and 2c wide. For the sake of simplicity the source w i l l be assumed to be a self-luminous gas extending indefinitely i n a l l directions outward from the s l i t . This may be experimentally realized f o r lateral extension by making the Raman tube everywhere of diameter sufficient to include the planes T and T_' , W and W , of the diagram below.  This i s necessary i n any case i f l i g h t  scattered from the walls and cooling jacket i s to be kept from entering the spectrograph. The effect of the f i n i t e length of the tube w i l l be developed later.  # J. Rud Nielson, Journal of the Optical Society of America, 20, 201 (1930)  Equations of the planes,T,- |xf - (a+c)z=cf T',-lxf + (a+c)z= -cf  W,- (yf - (b+s)z=sf W,-lyf + (b+s)z = -sf  S,- fxf - (a-c)z =-cf S',-txf + (a-c)z = cf  V,- fyf - (b-s)z =-sf V*,-lyf + (b-s)z = sf  A rectangular coordinate system with origin at the centre of the s l i t , X-axis across the width of the s l i t , Y-axis along the length of the s l i t , and Z-axis along the axis of the collimator has been adopted. The lines of intersection of planes S and S', at z = e = cf and of planes a-c V and V*, at z = g = sf , are of interest. b-s Only those parts of the source which l i e inside planes T and T*, W and W* can send any light through the collimating lens. Since there i s symmetry with respect to the Z-axis, only the octant for which z * 0, y ^ 0, x ^0, w i l l be considered.  - 22 The planes T,  S, S» and W,  V, V' divide t h i s octant into  twelve regions. These w i l l be indicated by a system of sub- and superscripts. Subscript 1 indicates z £ e "  2  •"  "  3  «  e< z * g z> g  Double superscripts i _ and p_ w i l l be used to indicate whether or not the region includes the Z-axis. For example f 1,°  would be a function pertaining to the region  for which e < z £ g ; 0 ^ x « -c + (a-c)z/f (inside S) and s - (b-s)z/f ± y £ S + (b + s)z/f If  (outside V', but of course inside W.)  I(x,y,z) denote the luminous intensity per unit volume of the  source, here considered constant, then the amount of light entering an element of area d^dc at the point (f>,«f, 0) of the s l i t , from an element of volume dxdydz at the point (x,y,z) of the source i s z  1  I(x,y,z)[ (x-o) + (y-<r) + z J  z dxdydzd/>d<r  (1)  4TT  Integration with respect to /o and C between limits which are obvious from the geometry and different for each region (see Nielson) yields an expression of the form 1  I(x,y,z) z0(x,y,z)  dxdydz  (2)  4TT  Using for abbreviation,1  A{(a-x) (b-y)l = tan" (a-x) (b-y) (f+z) [ (a-x) + (b-y)*f (f+z) ]* 2  2  uf(c-x) (b-y)] = tan"' (c-x) (b-y) [(f+z) (c-x) + z (b-y)%- z M f t z m 1  1  1  v  4  rf(a-x) (s-y)} = tan"' (a-x) (s-y) „ [z (a-x) + (ftz)* (s-y) + z (f+z)*J2  z  z  l  fo[(c-x) (s-y)} = tan"  1  (c-x) (s-y)  z [ (c-x)*+ (s-y)N- z*-]* and forming the other functions by the indicated substitutions, The functions (|> (x,y,z) of (2) become 0" =$a-x) (b-y)] X{(a-x) (b+y)} + A {(a+x) (b*yjj + A{ (a+x) (b+y)} +  4 f a - i ) (s-y))+ Aj(a-x) (b+y)} + ^ [ (a+x) (s-y)} 4 A{(a+x) (b+y)} 6t  0, =)*|c-x) (b-y)]+^j(c-x) (b+y)} + A j (a+x) (b-y)} + A ( (a+x) (b+y)] (s-yj}+ tf(c-x) (b+y)}+ ^ f (a+x) (s-y)}f * f (a+x) (b+y)j  0°°=p\lc-x)  (4"=^(c-x) (b-yjj+|^[(c-x) (b+y)}+ ^ J (c+x) (b-y)] pf(c+x) (b+y )j f  0"HP{(P-X) (s-y)}+ftj(c-x) (b+y)} + ^ J (c+x) (s-y)J+ /stj"(c+x) (b+y)j  (  t$''=p\{c-x)  (s-yjj+ [(c-x) (s+y)] + p[ (c+x) (s-y)} + ^[(c+x) (s+y)] (0  oL  ^ =pf(c-x) (s-y)}+^(c-x) (s+y)] + t>[(a+x) (s-y)] + t/[(a+x) (s+y)j  Integration of the functions (2) with respect to y and z_ keeping always i n the octant x£0, y 2 0 , z i O yields expressions of the form 1  I (x,y,z) (/> (z) dz  (3)  4TT  where there are twelve different functions if/ , one f o r each region. These are i n general very complicated, and to save space, only those referring to region _2, f o r which e< z£g w i l l be given. The others are similar, but this region i s of greatest interest, f o r i t i s here that most Raman tubes w i l l be situated. According to calculations from certain assumed values of f_, a_, b_, c_, s_, made later,  e = 1.35 cm. and g = 25.7 cm.  I f ^ s -z(f+z)A + zG(z) +• (f+z)J(z) - 0(z)  0  l£ * z*A + zC - zG(z) - zJ(z)  log k  - K(z) + 0(z) + 2sz*  ... . k (f+zfA - (f+z)B - (f+z)G(z) + H(z) - (f+z)J(z) + 0(z) H^-ztf+zjA  + zB - (f+z)C + D +• (f+z)G(z) - H(z) + zJ(z) + K(z) - 0(z) - 2s z* log k  Where,-  ^  A = es tan~ _ l  x  eg  £ log Ce'-sN g*c% g e ]' '+ ge 1  cs x  -1  [e*s + g*c + g^e -]*  l  e  /,  1  [ s + g ]*''  +-a logos'-* g ^ - t g -^]** es g [e'+ e ] ^  - 1 [ e'-sN g c 4 g^e*]* ge  1  t  x  l  1  x  cf log raV-v g*c 4 g d ] ^ eg g d ]^ d [ sV g ] ^  B = csf tan"] cs dg [d's'+g'cN  v  x  i  1  +  x  1  fs log [d*s% g*c * gMf't ds g [cV+ d*]*a  x  g d*]*  l  -  f [d sNgV+ gd  C csf tan"' es cf log f e * s +• e»k 4 e k ^ - f ck ek [e'-s - + c k + e^V e [s^k -]* x  x  x  a  1  v  4  x  fs log [e*s* + c ^ •+ e^k*] k [c + e*]^ 1  1  1,1  1  es - f_ [ e ^ 4 c^k 4 e*k ] ek 1  D , csf * tan" cs dk [d*s 4 c k + d*k*]*v  f^s k  x  1  l  yi  c f log [ d ' s N c^k* 4 d V ] d [s ^ k ]^ 1  v  1  log [ d ' s N c"k*4 dVl^tds £c»- + d ]*-  4  ck  1  - f _ [ d s + <?k -f d'k'J* dk l  x  x  x  G(z) = cs / f - z) tan~^_ cs (f A ° z/g) e Ik g/ [e s (fA -• z/g) 4 (f + z> ( c H e ) ] ^ %  l  2  1  c (f+z) log [e^sMfA - z / ) \ (f4zf ( c H -ef)]Vc(f-rz) e *~ CsMfA - z/g)"+ (f+z)-J^ f i  x  + s(fA - z/g) log re^sMfA - V g ) % (f+z)* (c"4e )]^es(f/k-z/g) (f + z)[c + e J>i i  - 1 [ ( e s ( f A " z/g) + (f 4 z ) M c 4 & ) ] l  x  x  l  x  K  e J(z) _ cs (2 - z/e) tan"]! cs(2 - z/e) g £c g (2 - z/e) + z * ( s S g ^ ] ^ l  l  L  z  + c(2 - z/e) log C c V ( 2 - z/e)% z (s* + g )!^* cg(2 - z/e) fs» + g*j* 1  - 25 1  x  sz_ log Cc'*g*(2 - z/e)*t z (s -i- g^l^+'sz .g " [c (2 - z/e) * + z ]^ 1  1 [ 0 ^ ( 2 - z/e)" g  -  H(z) = csf +  +  1  zMs% eft]*  (t/k - z/g) tan"'  cf (f + z) log d + fs(f/k - z/g)  os(fA - z/g) r  [d's^f A - z/g) t-(f + z)*" (oN fl]*+o(f » z) [s*(fA .-cz/g)^ (f + z)*J*x  x  logrd*s (fA - z/g)% (f+z) |eS d^]^ds(£ " 2} (f + z) r ct d*J* g k  x  l  l  - f [ d V ( f A - z/g) - + (f-f z) (cN d ) J * d 1  K(z) = csf (2 - z/e) tan"' cs(2 - z/e) k Ce k (2 - z/e) + z (sV K")]*t  + cf (2 - z/e)  1  l  >  log fc'-k -(jg - z/e)*> z ^ s V k*)j^4 ok(2 - z/e) —  -  1  k ]^  £3*-+  7-  2  «fz log Cc*k (2 - z/e) + zMs -* k*)j' 4 sz k " CC- (2 - z/e) - +. z^jn. x  +  x  /v  2  1  l  - f [cV-{2 - z/e)* + z ( s N l £ ) ] k 0(z) = cs(2-z/e) (f/k-z/g)  / l  tan^ cs(2-z/e) (f/k-z/g) fsz*(f/k-z/g)%c (f +z)«- (2-z/e)>+ z (ftz)*]* l  1  r  v  + c(f+z) (2-z/e) log fsz*(f A - z / g ) \ c (f-fz) (2-z/e)4z {ttzfl + c(f t z) (2 [sMfA-z/g) + (f+z)*]V x  1  +-sz(fA-z/g) logf szKf A - z / g ) \ c\f +.z)** (2-z/eft zlf-cz)^sz(^ (f+z)C c (2-z/e) 4-z J/v l  v  l  ,  1  -[s^z^fA-z/g)^ c (f+z) (2-z/e) - zMf+z) "]^ L  +  e -  cf a -c  g  d-  cf a+  k = sf b+ s  =  sf b- s  %  1  _  s  - 26 It w i l l be observed that %  l  = f * A - fB - re + D  *  and i s independent of z and the same statement holds for the other regions; u  i.e.  y,+  1^4  * ip.oo  +ip/-_np^- 1^"«  _ =f  £  =  +  2  Li  y  3  +  j \ +  w  - fB - f C + D  A  This interesting result verifies Nielson* s theorem,The t o t a l amount of light entering the collimating lens through the s l i t i s the same f o r vertical sections of the source of equal length, and i s independent of the distance from the s l i t , provided that the section i n cludes a l l the space defined by the planes T, T', and W, W . By using approximations f*A  &  - fB - fC +• <P = 4 abcs  - 2ab£S_(a + b  c  1  + s)  f 4-  ft  4  -t- 65 abcs ( a S b  c + s^  1G5 abcs_(a -c -+ b s )+- 103 abcs (a + a*) (bSs*) f f* a  +  2  i  2  a  fc  To a f i r s t approximation then, we have that the light entering the collimating lens from a region of the source lying between the planes z=z,,  z =z 1 4TT  z  is I(x,y,z) •  4 abcs f  1  This i s for only one octant.  (z -z,)  —  a  •  (4)  •  The other three octants w i l l each contribute  an equal amount. Hence i f we write 2c= w to agree with Nielson's notation, (4) becomes, for a l l four octants of the source,1_ I(x,y,z) TT  2 absw f*  ( z - z,) t  which i s exactly the same as Nielson's result. The finer approximations show a deviation from the results yielded  - 27 by Nielson's formula when treated i n the same way, but the deviations are comparatively small; indeed the whole of the correction terms are small when one i s dealing with a collimator of long focal length. Numerical evaluations of the functions  (2) yield expressions  verifying Nielson's results from that process. The table below indicates the widths of the various regions at different distances from the s l i t .  These are calculated for a spectro-  graph for which 2c -=. 0.030 cm. height of s l i t  _  2s--0.50  cm.  width of collimator diaphragm - - - - - - - - - - 2a = 3.8  cm.  height of collimator diaphragm - - - -  2b --= 3.8  cm.  - - - - - - - - - - - f =:170  cm.  focal length of collimator  e= cf = 1.35 a -c  cm.  g- sf = 25.7 b -s  cm.  z dis- x, width of x boundary Xj.- X, y, width y boundary tance inner re- of outer width of of inner of outer from gion region outer region region slit region t  x  y*- y. width of outer region  1.0 cm. 0.0039 emu 0.026 cm. 0.022 cm. 0,24 cm.  0.26 cm. 0.022 cm.  1.35  0.0  0.050  0.030  0.24  0.27  0.030  10.0  0.096  0.13  0.032  0.15  0.38  0.22  25.7  0.27  0.31  0.035  0.0  0.58  0.58  30.0  0.32  0.35  0.035  0.041  0.63  0.59  60.0  0.65  0.69  0.40  0.33  1.01  0.68  AGKNOWLE33GMEHT  The writer wishes to acknowledge his indebtedness to Dr. A. M. Crooker for his advice and assistance i n both the problems herein discussed.  

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