Scattering of Potassium from Halogen Compounds at Hyperthermal Energies

A potassium atomic beam with energies from 0.5 to 12 eV has been produced by sputtering. The differential elastic cross sections for scattering from C6H12, CCl4, SiCl4, SnCl4, Cl2, and Br2 have been measured. The known behavior of these systems at thermal energies is reproduced to some extent, but there are distinct differences at higher energies for SnCl4, Cl2, and Br2. These may possibly be explained by the onset of nonadiabatic transitions between almost-crossing energy surfaces.