Energy spectrum of protons produced in collisional dissociation of fast H2+ ions

Abstract

Energy distributions of protons produced in dissociative collisions of H2+ with H2, Ar and Xe have been measured in the forward direction at 10 keV. An experimental method giving the corresponding excess kinetic energy spectrum in the centre-of-mass system of H2+ is briefly discussed. The measured spectra are explained in terms of electronic and vibrational transitions to dissociative states of the H2+ molecular ion. The dissociation cross section by vibrational transitions in the 1sσg state is estimated to be, respectively, σv = 1.4 × 10-18 cm2, σv = 4.3 × 10-18 cm2 and σv = 5 × 10-18 cm2 for hydrogen, argon and xenon targets. The dependence upon the target density is interpreted as a double collision dissociation process of the type H2+ -> H20* -> H+. The influence of ion source parameters is also studied. Comparison is made with theory and the agreement is found to be good if one makes allowance for the dependence of dissociation upon the internuclear axis orientation.