Ionization, excitation, and chemical reaction in uniform electric fields

In a previous communication, Part II, Lunt and Meek described the calculation of the energy efficiency, ƞ, for the excitation of the 3Σg+ state of the hydrogen molecule, transitions from which to the lowest triplet state, 3Σu+, are accompanied by the emission of the continuous spectrum; these values of ƞ refer to excitation effected by an electron swarm moving in a uniform electric field, X, through hydrogen molecules in the ground state at the pressure p. The calculations show that ƞ is a function of Xp-1 and are based on the assumption of a Maxwellian electron energy distribution, an approximate estimate for the probability cross-section for the excitation of the 3Σg+ state by electron impact, and Townsend’s data for the dependence of the electron drift velocity, W, and the mean electron energy, V¯, on Xp-1. Since the only optically allowed transition which molecules in the 3Σg + state can suffer is that giving rise to the continuous spectrum, it follows that the energy efficiency for the emission of this spectrum must be equal to that for the excitation of the 3Σg + state.