We report a new evidence of vibronic relaxation pathway in methyl-substituted benzyl radicals from the analysis of the origin bands of the vibronic emission spectra observed. The jet-cooled methyl-substituted benzyl radicals generated in a corona discharge experience stepwise vibrational relaxation to the vibrationless state within their own electronic states, from which the crossing from the D-2 to D-1 states is possible through vibronic coupling using the vibrational modes in the D, state. Thus, it has been turned out that the energy difference between the D2 and the D-1 states is an important factor in determining the efficiency of vibronic coupling. (c) 2006 Elsevier B.V. All rights reserved.