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Ab initio calculations and Franck-Condon simulation of the absorption spectra of GeCl2 including anharmonicity

Ab initio calculations and Franck-Condon simulation of the absorption spectra of GeCl2 including anharmonicity
Ab initio calculations and Franck-Condon simulation of the absorption spectra of GeCl2 including anharmonicity
Geometrical parameters, vibrational frequencies and relative electronic energies of the X(-1)A(1), a(-3)B(1) and A(1)B(1) states of GeCl2 have been calculated at the CCSD(T) and/or CASSCF/MRCI level with basis sets of up to aug-cc-pV5Z quality. Core electron correlation and relativistic contributions were also investigated. RCCSD(T)/aug-cc-pVQZ potential energy functions (PEFs) of the X(1)A(1) and a(3)B(1) states, and a CASSCF/MRCI/aug-cc-pVQZ PEF of the A(1)B(1) state of GeCl2 are reported. Anharmonic vibrational wavefunctions of these electronic states of GeCl2, obtained variationally using the computed PEFs, are employed to calculate the Franck-Condon factors (FCFs) of the a-X and A-X transitions of GeCl2. Simulated absorption spectra of these transitions based on the computed FCFs are compared with the corresponding experimental laser-induced fluorescence (LIF) spectra of Karolczak et al. [J. Chem. Phys. 1993, 98, 60-70]. Excellent agreement is obtained between the simulated absorption spectrum and observed LIF spectrum of the a-X transition of GeCl2 which confirms the molecular carrier, the electronic states involved and the vibrational assignments of the LIF spectrum. However, comparison between the simulated absorption spectrum and experimental LIF spectrum of the A-X transition of GeCl2 leads to a revision of vibrational assignments of the of the LIF spectrum and suggests that the X(1)A(1) state of GeCl2 was prepared in the experimental work, with a non-Boltzmann vibrational population distribution. The X(0,0,1) level is populated over 4000 times more than expected from a Boltzmann distribution at 60 K, which is appropriate for the relative population of the other low-lying vibrational levels, such as the X(1,0,0) and X(0,1,0) levels.
ab initio calculations, electronic structure, fluorescence spectroscopy, franck-condon factors, germaniumcorrelated molecular calculations, harmonic vibrational frequencies, triplet energy separations, gaussian-basis sets, germanium dichloride, emission-spectroscopy, fluorescence-spectra, states, surfaces, abinitio
1439-4235
719-731
Mok, Daniel K. W.
1bbfba3e-c2e8-4225-8e07-cb6208ad83e1
Chau, Foo-tim
e15ec394-d11b-4cbe-91f3-cdac037d9d0e
Lee, Edmond P. F.
c54ce72b-3148-46ac-83fd-2d83d23d485f
Dyke, John M.
ffa1efaf-0eb1-4f69-94ef-b276534b5a57
Mok, Daniel K. W.
1bbfba3e-c2e8-4225-8e07-cb6208ad83e1
Chau, Foo-tim
e15ec394-d11b-4cbe-91f3-cdac037d9d0e
Lee, Edmond P. F.
c54ce72b-3148-46ac-83fd-2d83d23d485f
Dyke, John M.
ffa1efaf-0eb1-4f69-94ef-b276534b5a57

Mok, Daniel K. W., Chau, Foo-tim, Lee, Edmond P. F. and Dyke, John M. (2005) Ab initio calculations and Franck-Condon simulation of the absorption spectra of GeCl2 including anharmonicity. ChemPhysChem, 6 (4), 719-731. (doi:10.1002/cphc.200400489).

Record type: Article

Abstract

Geometrical parameters, vibrational frequencies and relative electronic energies of the X(-1)A(1), a(-3)B(1) and A(1)B(1) states of GeCl2 have been calculated at the CCSD(T) and/or CASSCF/MRCI level with basis sets of up to aug-cc-pV5Z quality. Core electron correlation and relativistic contributions were also investigated. RCCSD(T)/aug-cc-pVQZ potential energy functions (PEFs) of the X(1)A(1) and a(3)B(1) states, and a CASSCF/MRCI/aug-cc-pVQZ PEF of the A(1)B(1) state of GeCl2 are reported. Anharmonic vibrational wavefunctions of these electronic states of GeCl2, obtained variationally using the computed PEFs, are employed to calculate the Franck-Condon factors (FCFs) of the a-X and A-X transitions of GeCl2. Simulated absorption spectra of these transitions based on the computed FCFs are compared with the corresponding experimental laser-induced fluorescence (LIF) spectra of Karolczak et al. [J. Chem. Phys. 1993, 98, 60-70]. Excellent agreement is obtained between the simulated absorption spectrum and observed LIF spectrum of the a-X transition of GeCl2 which confirms the molecular carrier, the electronic states involved and the vibrational assignments of the LIF spectrum. However, comparison between the simulated absorption spectrum and experimental LIF spectrum of the A-X transition of GeCl2 leads to a revision of vibrational assignments of the of the LIF spectrum and suggests that the X(1)A(1) state of GeCl2 was prepared in the experimental work, with a non-Boltzmann vibrational population distribution. The X(0,0,1) level is populated over 4000 times more than expected from a Boltzmann distribution at 60 K, which is appropriate for the relative population of the other low-lying vibrational levels, such as the X(1,0,0) and X(0,1,0) levels.

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More information

Published date: 1 April 2005
Keywords: ab initio calculations, electronic structure, fluorescence spectroscopy, franck-condon factors, germaniumcorrelated molecular calculations, harmonic vibrational frequencies, triplet energy separations, gaussian-basis sets, germanium dichloride, emission-spectroscopy, fluorescence-spectra, states, surfaces, abinitio

Identifiers

Local EPrints ID: 20868
URI: http://eprints.soton.ac.uk/id/eprint/20868
ISSN: 1439-4235
PURE UUID: aa7ecb5f-9b3a-40d2-9a2e-80bd8262266a

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Date deposited: 02 Mar 2006
Last modified: 15 Jul 2019 19:25

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