Doublet rotational energy transfer of the SH (X 2Π, v′′ = 0) state by collisions with Ar

Abstract

The rotational energy transfer (RET) by Ar collisions within the SH X ²Π (v′′ = 0, J′′ = 0.5–10.5) state is characterized. The integral cross sections as a function of collision energy for each rotational transition are calculated using a quantum scattering method in which the constructed potential energy functions are based on a ground state potential energy surface (PES) reported previously. On the other hand, a laser-induced excitation fluorescence technique is employed to monitor the relaxation of the rotational population as a function of photolysis-probe delay time following the photodissociation of H₂S at 248 nm. The rotational population evolution is comparable to its theoretical counterpart based on calculated Λ-resolved RET rate constants. The propensity in Λ-resolved RET transitions is found to approximately resemble the case of OH(X ²Π, v′′ = 0) + Ar. The Λ-averaged RET collisions are also analyzed and result in several propensity rules in the transitions. Most propensity rules are similar to those observed in the collisions of SH(A ²Σ⁺) by Ar. However, the behavior of the conserving ratio, defined as rate constants for spin–orbit conserving transition divided by those for spin–orbit changing transition, shows distinct difference from those described by Hund's case (b).