Velocity Distribution of Metastable H Atoms Produced by Dissociative Excitation ofH2

Abstract

The velocity spectrum of metastable H(25) atoms produced by electron bombardment of H2 has been measured by a time-of-night technique. Two distinct groups of metastables have been detected. The slower atoms are interpreted as arising from transitions to attractive states just above the H(lS)-{-H.(2S) dissociation limit. The faster atoms are thought to arise from transitions to doubly excited repulsive states which have not previously been detected.

Dissociation of Molecules by Slow Electrons

“…All of the data show an unexpected cutoff on the low-energy side of the slow group of 2s atoms. It was first (97) suggested that the deficiency in the low-energy tail of the "slow" metastables could be accounted for if those states which mainly contribute to the production of slow metastables possessed a potential maxima at large internuclear separation. The fact that all of the data show a low-energy cutoff in the "slow" H(2s) distribution appears somewhat controversial [see· the comments by Glass-Maujean(80)j.…”

Fast metastable hydrogen atoms from H2molecules: twin atoms

“…1) is equivalent to the classical one [29] for timeof-flight (TOF) studies of H(2s) produced by electron impact on H 2 , i.e., a hydrogen jet crossing at right angles with an electron beam. To reduce the spread of the velocity distribution of the hydrogen molecules, as well as to use well-defined initial molecular states and have sufficient target density, the hydrogen beam is produced by a Campargue-type supersonic jet source [30].…”

Ab initiocalculations of perturbed core-excited resonances in H2associated with H ,n=3: analogies and differences with doubly-excited helium

“…Core-excited autoionization resonances in H 2 were first discovered experimentally in 1967 by Leventhal et al [1] in observations of metastable H(2s) atoms produced by electron impact and they were first characterized theoretically in 1969 by O'Malley [2]. Even earlier, in 1961, Davidson [3] deduced the double-minimum nature of the first excited 1 AE þ g state of H 2 from quantumchemical calculations, thus obtaining indirect evidence for the lowest core-excited resonance of this molecule which, for R>3 au, becomes electronically bound and produces the outer well of the double minimum state.…”