Dissociative excitation of H2: Spectral line shapes and electron impact cross sections of the Balmer lines

Abstract

The Balmer lines of H, when produced by electron impact dissociative ionization of low pressure H2, are much broader than the Doppler width of thermal H atoms. Indeed, they each have (a) a central peak and (b) broad wings, which result from two different groups of dissociative states. Excitation cross sections show structure as a function of electron energy. This helps to identify the states as follows; Predissociated and directly dissociated Rydberg states produce the central peaks and doubly excited states produce the wings.