Tai-Yuan David Lin

High-resolution fluorescence excitation spectra of jet-cooled benzyl and p-methylbenzyl radicals

Abstract High-resolution, rotationally resolved, laser-induced, fluorescence excitation spectra of the A 1 and 6a 1 0 bands of benzyl and the 0 0 0 band of p -methylbenzyl radicals were obtained in supersonic expansions. All three spectra were assigned and fit, using the rigid rotor Hamiltonian as well as methyl group internal rotation theory. The results of the rotational analysis provide good rotation constants for benzyl and p -methylbenzyl and establish unambiguously that the symmetry of the excited electronic state in this transition of p -methylbenzyl is 2 A 2 (in C 2v ). The heights of torsional barriers that hinder the internal rotation of the methyl group in p -methylbenzyl also are determined. The torsional results are compared to those obtained previously for this radical in a vibrational analysis and to other open shell radicals.

The laser-induced fluorescence spectra of jet-cooled arylmethyl radicals

Abstract Laser-induced fluorescence excitation and resolved emission spectra have been observed from the arylmethyl radicals, triphenylmethyl, diphenylmethyl, diphenylchloromethyl, and diphenylethyl. The free-jet-cooled radicals exhibit spectra with rich but well resolved vibrational structure, some of which is likely attributable to hindered twisting of the phenyl rings. Precise frequencies for the origins of the electronic transitions as well as fluorescence lifetimes for these radicals are reported.