Optical Selectivity and Absence of Intramolecular Vibrational Redistribution in Near-Resonance Laser Excitation

摘要

The problem of optical selectivity in laser excitation of polyatomic molecules and the elimination of intramolecular vibrational redistribution (IVR) processes is discussed. The recent prediction by Tannor, Blanco, and Heller, that off-resonance excitation may achieve such a selectivity in alkylbenzenes, is known to have some serious difficulties, since it is based on the assumption that the doorway state in these systems is localized in the benzene ring and that a dynamical IVR takes place. This assumption is not supported by the existing experimental data. Moreover, our ealier analysis shows that elimination of IVR may be achieved only when the excitation is detuned away from any molecular state (not just the doorway state). When the quasicontinuum of background molecular levels is properly taken into account, the apparent selectivity predicted by TBH disappears. (Reprints)