ChemInform Abstract: STATE‐TO‐STATE DYNAMICS OF IR MULTIPHOTON ABSORPTION IN THE A1A2 STATE OF THIOPHOSGENE: ABSORPTION CROSS SECTIONS

Abstract

Infrared multiphoton absorption (IRMPA) in the first excited singlet state of Cl2CS has been studied. Absolute cross sections for absorption to a fixed energy level, the nonradiative limit, from initial levels of increasing energy have been obtained. Although intuition suggests that as the energy required to reach the nonradiative limit decreases the apparent cross section should increase, this is not observed. Instead, the relative probability of absorption from all initial states is nearly the same as that from the ground vibrational level. Because the density of states in Cl2CS (? 1A2) is higher at 3000 cm−1 than in SF6, where intermode coupling is postulated to be important in the dynamics of absorption, the results suggest that at energies ?2500 cm−1 intramolecular relaxation is competitive with absorption. This interpretation is in agreement with predictions from the current theory of IRMPA.