Integral cross sections for electron-impact ionization–excitation of laser-excited barium

Abstract

We have measured electron-impact ionization–excitation (IE) cross sections for the Ba+ (…6p 2P) level out of the excited (…6s5d 1, 3D1, 2) and (…6s6p 1P1) levels of the neutral Ba atom in the energy range of 20–50 eV. Cross sections for IE out of the (…6s6p 1P1) level are approximately 50% larger than those from the (…6s2 1S0) ground state, while cross sections for IE out of the D levels are approximately 50% that of IE out of the ground state. The dependence of these cross sections on the initial P state alignment has been found to be small.