Penning ionization of argon by metastable helium atoms : a study of the energy and angular distributions of the ejected electrons

Abstract

Experimental measurements are reported for the Penning ionization of an argon target by impact of metastable helium atoms. The energy spectra of the ejected electrons are obtained at a series of angles in the range 30° to 90°, and the intensities due to the different metastable states compared

Detailed electron spectrometric study of the ionization of H2 by He* (21 S, 23 S)

“…Electron energy spectrum for He*(2~S, 23S)+H2(v"=0) Penning ionization, measured with apparatus II, fit calculation of the vibrational peaks (smooth curves), and residuals between data and sum fit pact of scattered metastabtes (see also, e.g., [9]. Comparison with the earlier PIES data [7,14], which exhibit much higher background below the true gas phase PIES signal, leads to the conclusion that any broad underlying "background", which might be due to gas phase ionization processes, as discussed by Tuffin et al at some length [14,46], is a negligible component under single collision conditions, as realized in the present work. The mixed He*(21S, 23S)+H2 spectrum, measured in apparatus II with an effective resolution of about 35 meV (FWHM) and presented in Fig.…”

“…3.1). For comparison, we have listed the previous published PIES results [6,14], the Franck-Condon factors fv, 0 and the theoretical vibrational populations P(v'; Heir) for HeI~(58.4 nm) photoionization of H2, reported by ONeil and Reinhardt [,50] on the basis of one of the most elaborate calculations carried out so far. The He* (23S) + H z results of Hotop and Niehaus [6], derived from an integral spectrum, which was obtained with a retarding field energy analyzer, show the correct trend, but are somewhat high at v'=0 and low at v'= 3, 4.…”

“…In particular, the four electron systems He* (21 S) + H2 and He* (23S) + H 2 have been investigated by several complementary experimental methods [3, 6, 7, 10, 13--25] and by ab initio theory [26][27][28][29][30]. PIES of H 2 with mixed metastable He*(21S, 23S) beams was carried out by Cermak [13], Yee et al [7], Tuffin et al [14], and Hotop [3]. Quantitative PIES results with a state-selected He*(23S) beam were reported by Hotop and Niehaus [6] and Mfinzer and Niehaus [10].…”

“…Previous PIES work on He*(21S, 23S)+He was hampered by lack of metastable state selection [3,7,13,14], high background rising towards lower electron energies [-6, 7, 13, 14], and, in part, by insufficient resolution [13]. The only published quantitative information on P(v') is due to Hotop and Niehaus [6] for He*(23S)+H2(v'=O--6) and Tuffin et al [-14] for He*(21S)+Hz(v'=O-2).…”

Ion Heating in Dusty Plasma of Noble Gas Mixtures

“…Experimental measurements confirmed that inelastic collisions (both excitation and ionization) play a key role on EEDF when two noble gases are mixed. Ionization of argon by metastable helium atoms is also known to be important energy transfer process in low helium-argon discharges [7].…”