Destruction of Metastable Helium Atoms in Binary Collisions

Abstract

A calculation of the cross section for the reaction He′+He′=He+He⁺+e (destruction of the metastable 2³S state by ionization) has been performed by means of the perturbed stationary state method. The cross section obtained is of the order of magnitude 10^—18 cm² at room temperature and increases slowly with decreasing kinetic energy of the colliding particles. The magnitude of the cross section fits well with a tentative scheme which considers processes of the type A′+B=A+B⁺+e as being intermediate between true resonance collisions and nonresonance collisions. It disagrees by 4 orders of magnitude with experimental findings [A. V. Phelps and J. P. Molnar, Phys. Rev. 89, 1202 (1953)]. The reason for this discrepancy is not known.