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Crystalline state photoreaction in 4‐methylcinnamic acid: a Raman phonon spectroscopic study
Author(s) -
Ghosh Manash,
Chakrabarti Subhasis,
Misra T. N.
Publication year - 1998
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/(sici)1097-4555(199804)29:4<263::aid-jrs233>3.0.co;2-n
Subject(s) - phonon , raman spectroscopy , chemistry , intramolecular force , exciton , lattice (music) , crystal (programming language) , crystal structure , excitation , spectroscopy , crystallography , photochemistry , molecular physics , condensed matter physics , optics , stereochemistry , physics , quantum mechanics , computer science , acoustics , programming language
The solid‐state photodimerization reaction mechanism in 4‐methylcinnamic acid crystal was investigated. Raman and infrared spectroscopy were used to study the intramolecular vibrations of the reactant and the product in order to characterize them. The absence of any large Stokes shift between the excitation and emission bands of the monomer crystal shows that the exciton–phonon coupling is weak. Raman phonon spectroscopic studies reveal that the reaction proceeds by a homogeneous mechanism in the initial stage and subsequently by a heterogeneous mechanism. The appearance of new sharp phonon bands suggests that the product lattice is ordered. No mode softening is observed. Hence the reaction seems to be topochemically controlled and lattice phonons do not take part in the reaction. © 1998 John Wiley & Sons, Ltd.