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.