Helium Molecular Energy States as Detected by Collisions of the Second Kind in Helium

Abstract

From a survey of the literature on spectra enhanced by collisions of the second kind, which take place in helium, evidence is presented for the existence in measurable concentrations of both the helium molecule-ion and the helium metastable molecule. From the intensity distribution of the enhanced spectra, the repulsive energy between two helium atoms at separations of 1.052A and 1.090A is derived to be 6.8 volts and 5.8 volts, respectively. The rates of formation of the molecular states are discussed in the special case of a steady-state discharge and the molecular states are shown to be very probable at high pressures. From this it is shown that the ion whose mobility is found to be 21.4 ${\mathrm{cm}}^{2}$/sec. volt is probably that of ${\mathrm{He}}_{2}^{+}$ in helium and, hence, the discrepancy between the theoretical and experimental values of the mobilities can be removed by such an interpretation. The existence of neon molecules is also suggested.