Dissociative electron capture of H2+ into H− fragments

Lee, A.R. and Jonathan, P. and Brenton, A.G. and Beynon, J.H. (1987) Dissociative electron capture of H2+ into H− fragments. International Journal of Mass Spectrometry and Ion Processes, 75 (3). pp. 329-343. ISSN 0168-1176

Abstract

Translational energy spectra of H− ions have been measured for capture dissociation of 6 keV H2+ molecular ions in collision with H2 gas. Voltage separation of the ion spectra has been obtained by the application of a biasing potential to the collision gas cell, allowing the sequence of processes taking place in different regions of the spectrometer to be identified. The energy release distribution of the H− spectra and a correlation with the corresponding component of the H+ spectra indicate that the majority of H− are produced from single electron capture-dissociation of H2+ in a double-collision mechanism, H2+ + H2 → H2* + [H2+] and H2* + H2 → H− + H+ + [H2], in which high Rydberg states of the H2* molecule are involved. The H− and corresponding H+ spectral peaks are narrow, with an FWHM of ∼ 0.14 eV in the centre-of-mass system for the H+ and H− ions released from dissociation of H2*, consistent with the suggested mechanism.