TITLE

Rotationally resolved structures in the fifth and sixth torsional states of à [sup 1]A[sup ″] acetaldehyde: Internal rotation above the torsional barrier

AUTHOR(S)
Chou, Yung-Ching; Huang, Cheng-Liang; Chen, I-Chia; Ni, Chi-Kung; Kung, A. H.
PUB. DATE
November 2002
SOURCE
Journal of Chemical Physics;11/1/2002, Vol. 117 Issue 17, p7906
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The fluorescence excitation spectrum of acetaldehyde in its transition ùA'-&Xtilde;¹A' is analyzed for torsional states above the barrier. States with torsional vibrational quantum numbers v[sub t]=5A, 5E, and 6A at term energies 660-927 cm[sup -1] are assigned. This region is 100-370 cm[sup -1] above the torsional barrier. These states lie between the limits of torsional vibrational motion and free internal rotor motion, so that the close-lying 5A[sub 2] and 6A[sub 1] states mix for K>0, and K states in the E sublevel are widely split. From an analysis of calculated eigenfunctions, the composition of K=1 sublevels reaches nearly equal proportions of odd (A[sub 2]) and even (A[sub 1]) torsional wave functions when levels exceed the top of the torsional barrier, whereas the K=1 eigenfunctions of v[sub t]=4A[sub 1] lying near consists of mostly even (A[sub 1]) functions. Avoided crossings with ΔK=0 and Δm=0 mod 3 selection rules are observed between K=2, E sublevels of 14[sup 0+] 15[sup 4] and 14[sup 0+] 15[sup 5] and between K=2, E sublevels of 14[sup 0-] 15[sup 4] and 14[sup 0-]15[sup 5]. The K energy-level structure of 14[sup 0+] 15[sup 5] deviates significantly from the expected parabolic shape. The K structures and the K state at the lowest energy differ appreciably for the two inversion doublets 14[sup 0+] and 14[sup 0-].
ACCESSION #
7532248

 

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