Intensity of the → symmetry-forbidden electronic transition in acetone by direct vibronic coupling mechanism

Rocha, Alexandre B.; Bielschowsky, Carlos Eduardo

doi:10.1016/s0009-2614(01)00213-5

Cited by 16 publications

(13 citation statements)

References 20 publications

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“…The published works have concentrated on the first excited singlet, [41][42][43][44][45] which is known to be, as in formaldehyde, the 1 ͑n → * ͒ state, or on the vertical transitions energies. The published works have concentrated on the first excited singlet, [41][42][43][44][45] which is known to be, as in formaldehyde, the 1 ͑n → * ͒ state, or on the vertical transitions energies.…”

Section: B General Considerations On the Excited Statesmentioning

confidence: 99%

Ab initio n-electron valence state perturbation theory study of the adiabatic transitions in carbonyl molecules: Formaldehyde, acetaldehyde, and acetone

Angeli

Borini

Ferrighi

et al. 2005

The Journal of Chemical Physics

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The application of the recently developed second-order n-electron valence state perturbation theory (NEVPT2) to small carbonyl molecules (formaldehyde, acetaldehyde, and acetone) is presented. The adiabatic transition energies are computed for the singlet and triplet n-->pi(*), pi-->pi(*), and sigma-->pi(*) states performing a full geometry optimization of the relevant states at the single state CASSCF level and taking into account the zero point energy correction in the harmonic approximation. The agreement with the known experimental values and with previously published high level calculations confirms that NEVPT2 is an efficient tool to be used for the interpretation of molecular electronic spectra. Moreover, different insight into the nature of the excited states has been obtained. Some of the transitions presented here have never been theoretically computed previously [(3)(pi-->pi(*)) and (3)(sigma-->pi(*)) adiabatic transitions in acetaldehyde and acetone] or have been studied only using moderate level (single reference based) ab initio methods (all adiabatic transitions in acetaldehyde). In the present work a consistent disagreement between NEVPT2 and experiment has been found for the (3)(pi-->pi(*)) adiabatic transition in all molecules: this result is attributed to the low intensity of the transition to the first vibrational levels of the excited state. The n-->pi(*) singlet and triplet vertical transition energies are also reported for all the molecules.

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Section: B General Considerations On the Excited Statesmentioning

confidence: 99%

Ab initio n-electron valence state perturbation theory study of the adiabatic transitions in carbonyl molecules: Formaldehyde, acetaldehyde, and acetone

Angeli

Borini

Ferrighi

et al. 2005

The Journal of Chemical Physics

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“…Note that, for the expansion of the transition dipole squared in Eq. (8), it is necessary to consider only positive values of the displacement along a normal coordinate since M 2 0k (Q L ) is an even function [25] of the normal modes considered here.…”

Section: A Benzene C 6 Hmentioning

confidence: 99%

“…The electronic dipole transition moments, necessary to obtain the OOS, were calculated with the multireference configuration interaction MRCI/6-311+G method. A total of 72821 configurations were used for the MRCI [25], which used molecular orbitals constructed with the modified virtual orbital (MVO) approach [59]. The vertical energy thus obtained for the n → π transition was 4.43 eV, the harmonic frequencies were scaled by 0.9496 [60], values used for the OOS calculation.…”

Section: B Formaldehyde H 2 Comentioning

confidence: 99%

“…This article reviews previously employed methods to study several electronic transitions, valence or inner-shell, optically forbidden or not, through photon absorption [24][25][26][27][28] and electron impact [29], enhancing intensity through vibronic coupling. We illustrate its usefulness through the valence transitions of benzene (C 6 H 6 ) [28], formaldehyde (H 2 CO) [24], acetone (C 3 H 6 O) [25] and formic acid (HCOOH) [30] that we have studied.…”

Section: Introductionmentioning

confidence: 99%

“…We illustrate its usefulness through the valence transitions of benzene (C 6 H 6 ) [28], formaldehyde (H 2 CO) [24], acetone (C 3 H 6 O) [25] and formic acid (HCOOH) [30] that we have studied.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical investigations on valence vibronic transitions

Borges¹,

Rocha²,

Bielschowsky³

2005

Braz. J. Phys.

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This article reviews previously employed methods to study several valence electronic transitions, optically forbidden or not, enhancing intensity through vibronic coupling. Electronic transition dipole moments were calculated using several ab initio methods including electron correlation. In this method the square of the electronic transition dipole moments are directly calculated along the normal coordinates of vibration and then expanded with a polynomial function. Afterwards, analytical vibrational integration using harmonic wave functions, of the square of the transition moments function, allows us to obtain partial (i.e. for each vibrational mode) and total optical oscillator strengths (OOS), for the vibronic transition of interest. We illustrate the accuracy of the method through valence transitions of benzene (C 6 H 6 ), formaldehyde (H 2 CO), acetone (C 3 H 6 O) and formic acid (HCOOH).

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