Total Cross Sections for the Scattering of Potassium by He, Ne, Ar, Xe, andH2in the Thermal Energy Range

Abstract

Absolute values of the cross sections for the scattering of potassium by helium, neon, argon, xenon, and molecular hydrogen have been determined in the thermal energy range. The atomic beam was velocity-selected using a Stern-Gerlach magnet with a resolution of approximately 10%. A capillary flow method was used to determine the target-gas density with resonably high accuracy. Temperature effects of the target gas were taken into account, using the tables of Berkling et al., and the target-gas temperature was varied to extend the relative-velocity range employed. The potential constants for K-A and K-Xe are in reasonable agreement with those obtained from the cross-section measurements of Rothe and Bernstein, and Helbing and Pauly. The values obtained for K-A, K-Xe, and K-${\mathrm{H}}_2$ are 571.6, 1024, and 106.2×${10}^{-60\mathrm{}}$ erg ${\mathrm{cm}}^6$, respectively; K-Ne exhibits an approximate $v^{-\frac{2}{3}}$ velocity dependence over the range 400 to 1450 m/sec; while the K-He cross section is essentially velocity-independent over the range 650 to 2000 m/sec.