NUMERICAL STUDY OF SELECTIVE DOUBLE-ELECTRON CAPTURE BY ALPHA-PARTICLES IN COLLISIONS WITH HYDROGEN MOLECULES IN A COOLED PLASMA

A numerical study based on a collisional radiative model is performed to understand the enhanced He I (n = 3 --> n = 2) line intensities rec ently observed in an He plasma in contact with hydrogen gas: accidenta l resonant double-electron capture into the excited states by alpha pa rticles in the process He2+ + H-2 --> He(1s3l) + H+ + H+ whose cross- sections are very large at low energies. The calculated results agree fairly well with the observed temporal evolutions of the enhanced He I line intensities. (C) 1997 Elsevier Science S.A.