Electron impact dissociation cross sections in hydrogen and deuterium, leading to Balmer alpha and beta emission

Dissociation of H 2 and D 2 by electron impact, leading to the emission of Balmer alpha and beta radiation, has been studied for electron energies up to 100 eV. Normalised excitation functions, their isotope ratio, and polarisation are reported. Care was taken to eliminate magnetic and electric fields, and to allow for molecular radiation near the Balmer lines. Compared with previous reported work the shape of the cross sections found is substantially the same, while showing an additional threshold near 43 eV, but the isotope ratios are markedly different at low energies while agreeing at higher energies. Complete polarisation measurements are reported for the first time.