Low energy differential and integral electron-impact cross sections for the2s22p4 3P →2p33s 3So excitation in atomic oxygen

Abstract

Differential and integral cross sections (ICSs) for excitation in atomic oxygen have been measured at electron-impact energies of15, 17.5, 20, 22.5 and 27.5 eV. Differential measurements were conducted with aconventional electron energy-loss spectrometer and a microwave discharge sourceof atomic oxygen. Relative differential cross sections (DCSs) were determinedbetween 15 and 30 eV impact energy. With the help of theoretical predictionsof the shape of the DCS at large angles, measured results were extrapolated to180° scattering angle and relative ICSs were deduced. The relative excitation function was normalizedto the 30 eV impact energy ICS given by Kanik et al (2001 J. Phys. B: At. Mol. Opt. Phys. 342647). Normalization of the ICS values allowed the measured DCSs to be put on theabsolute scale. Theoretical calculations of the DCSs were carried out using theR-matrixwith the pseudostates approach. A total of 22 spectroscopic bound and autoionizing states,together with 19 pseudostates, were included in the close-coupling expansion. Thepseudostates were chosen to simulate continuum target states. Theoretical results, alongwith other available experimental data, have been compared with the current experimentalresults.