Improved study of the ionization of hydrogen atoms in thermal energy collisions with metastable He(23S) atoms

The first electron spectrometric study of the ionizing reaction of metastable He(23S1) atoms with ground state hydrogen atoms has been carried out with sufficiently high resolution to partially resolve the rotational structure due to formation of rovibrationally excited HeH+(υ,J) ions at two different beam source temperatures (300 K and 90 K). The electron energy spectrum has been reproduced in model quantum calculations, using a new large scale ab initio calculation of the He(23S)+H(12S) 2Σ-potential. The imaginary part has been adjusted to yield a satisfactory fit to the measured spectrum. The collision energy dependence of the associative ionization electron spectra and of the total and partial ionization cross sections is discussed in some detail. No significant signs for limitations of the used local complex potential method, indicated by results of an earlier study of the He(23S)+H(12S) system, have been found in the present work, in which the calculations were carried out with an improved and corrected program. (orig.)