Simulation of Ã 1B1→X̃ 1A1 CF2 single vibronic level emissions: Including anharmonic and Duschinsky effects

Abstract

CASSCF/MRCI/aug-cc-pVQZ͑no g͒ and RCCSD͑T͒/aug-cc-pVQZ potential energy functions were reported for the à 1 B 1 and X 1 A 1 states of CF 2 , respectively. Vibrational wave functions of the symmetric stretching and bending modes of the two states of CF 2 were obtained in variational calculations, employing Watson's Hamiltonian for a nonlinear molecule and anharmonic vibrational wave functions expressed as linear combinations of harmonic basis functions. Franck-Condon factors ͑FCFs͒ were computed for à 1 B 1 →X 1 A 1 CF 2 single vibronic level ͑SVL͒ emissions and the SVL emission spectra were simulated with the computed FCFs. When compared with the observed spectra, the simulated spectra obtained in the present investigation, which include allowance for anharmonicity and the Duschinsky effect, were found to be significantly superior to those reported previously, based on the harmonic oscillator model. Using the iterative Franck-Condon analysis procedure, with the geometry of the X 1 A 1 state fixed at the recently determined experimental equilibrium geometry, the geometry of the à 1 B 1 state of CF 2 , which gave the best match between simulated and observed spectra, was found to be r e (CF͒ϭ1.317 Å and e (FCF)ϭ121.25°.

Franck–Condon simulation of the photoelectron spectrum of AsCl2 and the photodetachment spectrum of AsCl employing UCCSD(T)‐F12a potential energy functions: IE and EA of AsCl2

“…those used in RCCSD(T) calculations), namely ACVTZ and ACVQZ (see Table 1 and footnotes d, e, f, and g for details), were used in UCCSD(T)-F12a and UCCSD(T)-F12b calculations, respectively. The combinations of the F12a variant of the UCCSD(T)-F12x method with the ACVTZ basis set, and of the F12b variant with the ACVQZ basis set, have followed the recommendation of the authors of MOLPRO (see MOLPRO online user manual 19 [30][31][32] and hence will not be repeated here. Nevertheless, some technical details specific to this study are summarized in Table 2.…”

The geometry of the NO2− anion: ab initio calculations and Franck–Condon analysis

“…Botschwina et al [15] are one of the few research groups performing anharmonic FCF calculations in this way. Recently, details of a few other types of anharmonic FCF methods have been published [12][13][14][16][17][18]. Franck-Condon factor calculations that consider anharmonicity effects will be the focus of our future work.…”

“…Geometry optimization and harmonic vibrational frequency calculations were carried out on theX 2 [8,[10][11][12][13][14] was also carried out.…”

Ab initio calculations and Franck–Condon analysis of photoelectron spectroscopy of CH3OO− and CD3OO−

“…With quantum chemical computing programs being readily available, geometries and normal modes of small to medium size molecules in different electronic states can now be calculated routinely. Based on these methods, numerous applications of FC calculations have been presented in the literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14], and most of these studies just focus on the interpretation of experimentally known spectra. Because the geometry difference between two electronic states is a major factor that influences FC intensities, the simulation of vibronic spectra of ployatomic molecules can be regarded as a valuable test with respect to the quality of calculated geometries and as a starting point to obtain improved structures.…”

“…In addition, spectral simulations of vibrational structure based on computed Franck-Condon factors (FCF) could provide fingerprint type identification of an observed spectrum, in terms of both the carrier and the electronic states in the transition (see, for examples, [9,10], and references therein). Also, it has been demonstrated that spectral simulations can be very useful in establishing vibrational assignments in an electronic spectrum observed with complex vibrational structure [1][2][3][4][5]7,10,11].…”