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Ab initio study on the electronic structures of styrene in the Franck‐Condon region
Author(s) -
Amatatsu Yoshiaki
Publication year - 2002
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10077
Subject(s) - complete active space , ab initio , chemistry , atomic physics , ring (chemistry) , benzene , styrene , ab initio quantum chemistry methods , multireference configuration interaction , excitation , ethylene , computational chemistry , molecular physics , physics , molecule , quantum mechanics , density functional theory , basis set , biochemistry , organic chemistry , copolymer , catalysis , polymer
The electronic structures of styrene in the Franck‐Condon region have been theoretically examined by means of ab initio complete active space self‐consistent field (CASSCF) and the second order multireference Møller‐Plesset calculations. The optimized structure of styrene in S 0 is planar but the torsional motion of the phenyl group is very floppy. The S 1 state is assigned to the local π–π* excitation within the benzene ring. On the other hand, S 2 , above S 1 by 0.561 eV, is assigned to a state that resembles the so‐called V‐state of ethylene. The transition intensity of S 0 –S 1 is weak, while that of S 0 –S 2 is strong. This is in good agreement with the experimental absorption spectrum where the S 0 –S 1 and S 0 –S 2 transitions are in the energy range of 290–220 nm. The optimized geometry of S 1 , characterized by an enlarged benzene ring and its vibrational analyses, further justifies the assignment of the S 1 state. © 2002 Wiley Periodicals, Inc. J Comput Chem 9: 928–937, 2002