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High resolution electronic spectra of some new transition metal-bearing molecules Rixon, Scott John
Abstract
Spectra of zirconium monocarbide (ZrC), zirconium methylidyne (ZrCH) and lanthanum imide (LaNH) are reported for the first time. All species have been produced under jet-cooled conditions by reaction of gaseous metal atoms with methane or ammonia and examined via laser-induced fluorescence. ZrC has several electronic states below 2500 cm-¹ : Χ³Σ⁺ and three ¹Σ⁺ states, which appear to represent all possible arrangements of two electrons in the nearly degenerate 11σ and 12 σ orbitals (from Zr 5sσ + C 2pσ). For Χ³Σ⁺ (r₀ = 1.807 Å), the small spin-spin constant (λ₀ = 0.514 cm-¹) and large Fermi contact parameter of ⁹¹Zr¹²C (I[sub zr] = 5/2) indicate the configuration (11σ)¹(12σ)¹ . The tightly bound a¹Σ⁺ state (T₀ = 187.83 cm-¹, r₀ = 1.739 Å) has the configuration (11σ)², while anomalous vibrational intervals and ¹²C / ¹³C isotope shifts of the other two states reveal their isosymmetry. This orbital scheme also accounts for the complex structure above 16000 cm-¹; identical, strongly interacting manifolds result from promoting either a electron to the same orbital. ZrCH has a ²П - Χ²Σ⁺ electronic system in the visible region analogous to that seen for isoelectronic ZrN, but they otherwise share little similarity. For Χ²Σ⁺, high-resolution rotational analyses give r 0 bond lengths, while dispersed fluorescence has characterised its vibrational structure. Conversely, many details remain unclear for the excited state. Upper state P = Λ+l+Σ values and Zr isotope shifts have been obtained for many subbands of ZrCH and ZrCD; ¹²C / ¹³C shifts have also been determined for some ZrCH bands. Unexpectedly small values of the spin-orbit constant and Zr-C stretching frequency, and the large Renner- Teller splitting in the 010-000 band are believed to be due to strong vibronic coupling with ²Σ and ²Δ states. The electronic structure of LaNH is similar to isoelectronic LaO, with the added complication of vibronic coupling between the Ã²П and B²Σ⁺ states. This is apparent from anomalies in the B²Σ⁺ - Χ²Σ⁺ hyperfine intensity profiles (I [sub La] = 7/2), the Hund's case (a) coupled B²Σ⁺ (0υ₂0) level structure and the large B²Σ⁺ state bending frequency.
Item Metadata
Title |
High resolution electronic spectra of some new transition metal-bearing molecules
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2004
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Description |
Spectra of zirconium monocarbide (ZrC), zirconium methylidyne (ZrCH) and
lanthanum imide (LaNH) are reported for the first time. All species have been produced under
jet-cooled conditions by reaction of gaseous metal atoms with methane or ammonia and
examined via laser-induced fluorescence.
ZrC has several electronic states below 2500 cm-¹ : Χ³Σ⁺ and three ¹Σ⁺ states, which
appear to represent all possible arrangements of two electrons in the nearly degenerate 11σ and
12 σ orbitals (from Zr 5sσ + C 2pσ). For Χ³Σ⁺ (r₀ = 1.807 Å), the small spin-spin constant (λ₀
= 0.514 cm-¹) and large Fermi contact parameter of ⁹¹Zr¹²C (I[sub zr] = 5/2) indicate the
configuration (11σ)¹(12σ)¹ . The tightly bound a¹Σ⁺ state (T₀ = 187.83 cm-¹, r₀ = 1.739 Å) has
the configuration (11σ)², while anomalous vibrational intervals and ¹²C / ¹³C isotope shifts of
the other two states reveal their isosymmetry. This orbital scheme also accounts for the
complex structure above 16000 cm-¹; identical, strongly interacting manifolds result from
promoting either a electron to the same orbital.
ZrCH has a ²П - Χ²Σ⁺ electronic system in the visible region analogous to that seen for
isoelectronic ZrN, but they otherwise share little similarity. For Χ²Σ⁺, high-resolution
rotational analyses give r 0 bond lengths, while dispersed fluorescence has characterised its
vibrational structure. Conversely, many details remain unclear for the excited state.
Upper
state P = Λ+l+Σ values and Zr isotope shifts have been obtained for many subbands of ZrCH
and ZrCD; ¹²C / ¹³C shifts have also been determined for some ZrCH bands. Unexpectedly
small values of the spin-orbit constant and Zr-C stretching frequency, and the large Renner-
Teller splitting in the 010-000 band are believed to be due to strong vibronic coupling with ²Σ
and ²Δ states.
The electronic structure of LaNH is similar to isoelectronic LaO, with the added
complication of vibronic coupling between the Ã²П and B²Σ⁺ states. This is apparent from
anomalies in the B²Σ⁺ - Χ²Σ⁺ hyperfine intensity profiles (I [sub La] = 7/2), the Hund's case (a)
coupled B²Σ⁺ (0υ₂0) level structure and the large B²Σ⁺ state bending frequency.
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Extent |
17019791 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-12-02
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0085503
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2004-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.