In:
The Journal of Chemical Physics, AIP Publishing, Vol. 88, No. 11 ( 1988-06-01), p. 6768-6777
Abstract:
The fluorescence excitation and several dispersed fluorescence spectra for supersonically cooled p-methyl-trans-stilbene and the two m-methyl-trans-stilbenes are presented. Despite significant spectral congestion present in these molecules which contain low frequency modes and internal rotation structure, nearly complete assignments of the excitation spectra are given. One notable transition is assigned as a combination of a nontotally symmetric vibration and a nontotally symmetric level of the methyl rotor. All three species have a ground state barrier to internal rotation of ∼28 cm−1. Excited state barriers and conformational changes observed on excitation are 150 cm−1 and 35° for p-Me, and 80 cm−1 and 60°, and 186 cm−1 and 30° for the two m-Me compounds. The p-Me compound shows a threefold barrier to internal rotation rather than a sixfold one, indicating that the two meta positions are inequivalent. The large differences in barrier height and conformational change on excitation between the two meta isomers, whose origins are separated by 207 cm−1, confirm this inequivalence.
Type of Medium:
Online Resource
ISSN:
0021-9606
,
1089-7690
Language:
English
Publisher:
AIP Publishing
Publication Date:
1988
detail.hit.zdb_id:
3113-6
detail.hit.zdb_id:
1473050-9
Permalink