Mass-Spectrometric Study of the Bimolecular Formation of Diatomic Argon Ion

Pulsed mass-spectrometric studies of the bimolecular formation of Ar2+ show that the reaction proceeds via three excited states of argon which have excitation functions that peak at 18, 28, and 65 eV. In kinetic studies, effective radiative lifetimes and specific reaction rates have been determined at these electron energies. The rather large rate constants observed (1.3–2.0×10−9 cm3 molecule−1·sec−1) yield collision diameters in good agreement with those predicted by simple theoretical considerations of the radii of argon atoms in the 3p5 4d and 3p5 5p configurations, such configurations being of the lowest energy compatible with the smallest reported appearance potential of 14.7 eV for Ar2+.