Electron excitation coefficients and cross sections for excited levels of argon and xenon ions

Abstract

In this paper, we present experimental results for the excitation coefficients of Ar+ and Xe+ ions to several excited states above their respective ground states. The data have been obtained from two different drift tubes and were analysed using Monte Carlo simulation, which involved an accurate representation of non-equilibrium effects and a complete set of initial cross sections. For some levels, it was possible to cover a sufficient range of E/N so that the electron energy dependent cross sections could be derived. For the remaining levels, normalization of the assumed shape of the cross sections could be performed by using excitation coefficients in a limited range of E/N. As expected, for all observed excited states, the cross section increases sharply from the threshold energy, reaches a maximum at about 40–50 eV and then decreases slowly for higher energies. The peak cross sections fall between 3 × 10−22 and 15 × 10−22 m2 for argon and between 3 × 10−22 and 21 × 10−22 m2 for xenon. The peak values of the cross sections are in reasonable agreement with the data previously obtained using the electron beam technique (binary collision), but the energy dependent profiles of the cross sections are significantly different. The absolute emission coefficients of three Xe2+ lines, excited from the ground state xenon atom, have also been deduced. They are about one order of magnitude smaller than those of the stronger Xe+ lines.