Experimental investigation of the rotational- and vibrational-state dependence of the HF–Rg interactions

Abstract

A systematic investigation of the rotational- and vibrational-state dependence of the HF-Rg (Rg = He, Ar, Kr, Xe) intermolecular interactions has been performed using the technique of light-induced drift. Data are presented of the relative change in collision rate upon excitation Δν/ν≡(νe−νg)/νe of HF with respect to Rg. We studied the P- and R-branch of the fundamental vibrational band (v=0→1) with the rotational quantum number J ranging from J=0 through 6 using a continuously tunable F-Center Laser (λ≊2.5 μm). The results indicate that v and J have independent additive influences upon the collision rate ν. This allows one to determine the v- and J-dependence of ν separately. It is found that, upon vibrational excitation v = 0 → 1, ν increases by ≊0.15% for HF-He; ≊1.0% for HF-Ar, Kr and ≊1.5% for HF-Xe. A remarkable J-dependence of ν is observed: for HF-Ar, Kr and Xe, the collision rate ν first decreases by ≊5% for J=0→1, subsequently reaches a minimum for J=2 and then increases again for higher J. By contrast, for HF-He, ν decreases monotonically for J=0 through 5 by ≊ 4%. The influence of the optically induced alignment of J is found to produce a minor contribution only.