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Refined analysis of Raman excitation profiles for cis ‐(CH) x and ‐(CD) x polymers
Author(s) -
Tarr Allan W.,
Siebrand Willem
Publication year - 1989
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250200403
Subject(s) - raman spectroscopy , excitation , isomerization , dispersion (optics) , chemistry , allowance (engineering) , distribution (mathematics) , molecular physics , analytical chemistry (journal) , bond length , atomic physics , crystallography , physics , optics , crystal structure , mathematics , mechanical engineering , mathematical analysis , biochemistry , chromatography , quantum mechanics , engineering , catalysis
Model calculations are reported aimed at interpreting the Raman excitation profiles observed by Lichtmann et al . They refine earlier calculations by Siebrand and Zgierski based on displaced harmonic oscillators. A distribution of conjugation lengths is introduced and the dependence of the model parameters, in particular the resonant state energy, on this length is investigated. This, together with an allowance for vibrational frequency changes and non‐Condon effects, yields a much improved fit to the observed profiles. The results suggest a narrow distribution of relatively short conjugation lengths (⩽20 double bonds), contrary to most earlier reported distributions based on the dispersion of Raman bands, but comparable to a distribution based on isomerization kinetics.