Differential cross sections and angular distributions of H-from dissociative electron attachment to H2 between 3.75 eV and 13 eV

An electron-impact spectrometer has been modified for the study of negative-ion fragments. This instrument has been used to observe differential cross sections and angular distributions of H- ions produced by dissociative attachment to H2 through the 2Σ+sub(u) and 2Σ+sub(g) resonances. The influence of thermal motion of the target molecules as well as momentum transfer on the angular distributions is examined. The measured angular distributions are analysed using the pure resonant scattering with potential scattering theoretical model which is discussed. The following information is extracted from this analysis. Firstly, the phaseshifts for non-resonant elastic scattering of the s- and d-waves are related by delta0 - delta2 approximately equals 1.35 rad in the 11 eV region and, secondly, the coupling matrix element of the d-wave is about 1.2 times larger than that of the s-wave for the 2Σ+sub(g) (1ssigmasub(g)) (2psigmasub(u))2 resonant state, and 1.8 times smaller for the 2Σ+sub(g) (1ssigmasub(g)) (2pπsub(u))2 resonant state. Vibrational structure observed in the differential cross section between 11.30 eV and 13.30 eV is interpreted as resulting from predissociation of the 'a' resonance bands by the H2-2Σ+sub(g) repulsive state. (author)