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Lidiya A. Koroleva, Alexandra V. Koroleva
Comparative analysis of the
capabilities of molecular spectroscopy methods in studying internal rotation
Abstract
Abstract: In the review the comparison of the methods used to study
internal rotation (IR) in the ground (S0) and excited (S1)
electronic states in the series of α,β-unsaturated carbonyl
compounds: R4R3C = CR2-COR1, where
R1 = H, R1 = F, R1 = CI; R2 = H, R2
= CH3,R2 = F; R3 = R4 =
H = CH3, is made. Differences in the values of (0-v)-transitions of
torsional vibration for s-trans- and s-cis-isomers for some studied compounds
are revealed in the methods of analysis of the vibrational structure of n-π*-transition
of high-resolution UV absorption spectra and IR-Fourier-spectra, used in the
study (IR) in (S0) electronic state. The reasons for such
differences are established. It is shown that in the (S0) state a
more reliable determination of the values of (0-v)-transitions of torsional
vibration of both isomeric forms of molecules was obtained in the method of
analysis of the vibrational structure of n-π*-transition of UV
absorption spectra. A new assignment for transitions of torsional vibration of
the s-trans isomer of acrolein in the spectrum of the Cavity Ringdown
Spectroscopy (CRDS) method in the excited (S1) state is proposed. It
is concluded that the method of analyzing the vibrational structure of n-π*-transition
of high-resolution UV absorption spectra of vapors of the studied compounds is
more reliable and accurate when studying (IR) in both electronic states.
Key words:ν – frequency of torsional vibration, v – vibrational
quantum number, ω – wave number, Deslandres table (DT), the
ground and excited electronic states
Copyright (C) Chemistry Dept., Moscow State University, 2002
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