Journal of Chemical Physics, Vol.105, No.15, 6375-6384, 1996
Experimental Investigation of the Rotational-State and Vibrational-State Dependence of the HF-Rg Interactions
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 Delta nu/nu=(nu(e)-nu(g))/nu(e) 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 (lambda approximate to 2.5 mu m). The results indicate that v and J have independent additive influences upon the collision rate nu. This allows one to determine the v- and J-dependence of nu separately. It is found that, upon vibrational excitation v = 0-->1, nu increases by approximate to 0.15% for HF-He; approximate to 1.0% for HF-Ar, Kr and approximate to 1.5% for HF-Xe. A remarkable J-dependence of nu is observed : for HF-Ar, Kr and Xe, the collision rate nu first decreases by approximate to 5% for J=0-->1, subsequently reaches a minimum for J=2 and then increases again for higher J. By contrast, for HF-He, nu decreases monotonically for J=0 through 5 by approximate to 4%. The influence of the optically induced alignment of J is found to produce a minor contribution only.
Keywords:LIGHT-INDUCED DRIFT;INFRARED-LASER SPECTROSCOPY;SCATTERING CROSS-SECTION;FREE-JET EXPANSION;FUNDAMENTAL BANDS;VANDERWAALS MOLECULES;INTERMOLECULAR FORCES;INELASTIC-SCATTERING;AR-HF;GAS