Out of resonance infrared fluorescence of SF6, 12CF3I, 13CF3I in quasicontinuum states. I

Abstract

IR fluorescence of SF6 has been monitored in the spectral range 700–1300 cm−1 with a high sensitivity device, after IR multiphoton excitation at several vibrational energies up to 17 000 cm−1. Preliminary results have also been obtained for 12CF3I and 13CF3I. The sensitivity achieved allows us to focus on the out of resonance fluorescence which turns out to be directly proportional to the local intramolecular couplings represented by the parameter γ(E→E′)=πρ(E′)‖V(E→E′)‖2. The method is partly free from an inhomogeneous contribution and the result can be compared to the Lorentzian model of intramolecular redistribution. It is shown that the γ(E→E′) parameter exhibits a hierarchy of structures, the strongest couplings leading mainly to a perturbative redistribution, while the weakest couplings are responsible for the dissipative redistribution. The homogeneous dissipative part γd appears to be smaller than 1–1.5 cm−1.