Spectroscopic Evidence of Vibronic Relaxation in Methyl Substituted Benzyl Radicals

摘要

Energy transfer and redistribution processes are believed to play important roles in explaining the reaction dynamics of large aromatic compounds,and have been studied for many decades.The benzyl radical is known to have close-lying 2~2B_2(D_2) and 1~2A_2(D_1) excited electronic states separated by about 22,000 cm~(-1) from the 1~2B_2(D_0) ground electronic state.Ring substitution is also expected to affect the energies of the two excited electronic states differently,which could be mixed by vibronic coupling.In methyl-substituted benzyl radicals,the electronic interaction between the methyl group and the benzene ring is undoubtedly of the second-order compared to that between the methylene group and the benzene ring,since the molecule has a planar structure of 7 delocalized pi electrons in which the CH_2 group contributes an electron.