PHOTOISOMERIZATION OF DIPHENYLBUTADIENE IN LOW-VISCOSITY NONPOLAR-SOLVENTS - EXPERIMENTAL MANIFESTATIONS OF MULTIDIMENSIONAL KRAMERS BEHAVIOR AND CLUSTER EFFECTS

被引:63
作者
GEHRKE, C
SCHROEDER, J
SCHWARZER, D
TROE, J
VOSS, F
机构
[1] Institut für Physikalische Chemie der Universität, Universität Göttingen, D-3400 Göttingen
关键词
D O I
10.1063/1.457697
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The photoisomerization of diphenylbutadiene was studied by picosecond absorption spectroscopy over wide pressure and temperature ranges in liquid and supercritical alkanes, CO2, SF6, and He. The reaction shows typical features of a thermal unimolecular reaction on the S1 potential energy surface. The rate can be expressed by a combination of standard unimolecular rate theory and Kramers-Smoluchowski theory. However, multidimensional behavior manifests itself in the transition to the gas phase low pressure range as well as to the high density Kramers-Smoluchowski range: in the former case, the low pressure limit of a unimolecular reaction of the polyatomic molecule is approached; in the latter case, the effective imaginary barrier frequency shows a marked apparent temperature dependence. The experiments also suggest contributions of reactant-solvent cluster interactions, which modify the barrier height even in nonpolar solvents. © 1990 American Institute of Physics.
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页码:4805 / 4816
页数:12
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