Does a Molecule Remember the Way It Was Energized?

Abstract

Intramolecular vibrational redistribution (IVR) is the key phenomenon in unimolecular decomposition of polyatomic molecules energized in collisions, by photon absorption, or formed by association of radical particles. On an ultrashort time scale, the excitation energy is localized at some place (bond) of the molecule. On a middle time scale, energy irreversibly flows from the excited place to the rest of the molecule. On a long time scale fluctuations of the internal energy are reminiscent of a quasiperiodic process. Almost all the relevant experimental data and model calculations suggest that the information concerning the place of excitation in the molecule is lost during 100 fs - 10 ps after excitation. It seems that due to the rapid IVR the laser selective chemistry has in general no promising perspectives.