ELECTRON DETACHMENT IN LOW-ENERGY COLLISIONS OF HALOGEN ANIONS WITH ATOMIC-HYDROGEN

Total electron-detachment cross sections sigma(e) for collisions of F-, Cl-, Br-, and I- with atomic hydrogen have been measured for relative collision energies E ranging from 0.1 to 20 eV. For F-, Cl-, and Br-, sigma(e), is found to decrease with increasing E and is fairly well described by a simple orbiting model in which an effective polarizability is used to describe the interaction of the anion with atomic hydrogen at small internuclear separations. For the system I-+H, sigma(e), increases with increasing collision energy. The measured sigma(e) for Cl-+H is also found to agree well with calculations based on an effective-range approximation. Charge-transfer cross sections have been measured for F-, Cl-, and I-+H and are found to be small.