Accession Number : AD0277175

Title :   AN EXPERIMENTAL STUDY OF ATOM-ION COLLISIONS PRODUCING LYMAN ALPHA RADIATION

Corporate Author : WASHINGTON UNIV SEATTLE

Personal Author(s) : DUNN,GORDON H.

Report Date : 11 APR 1962

Pagination or Media Count : 1

Abstract : An ion beam apparatus useful for studies of electron-ion and ion-neutral collisions was built and put into successful operation. Absolute cross sections for the production of Lyman alpha radiation from the impact of ions on neutrals were measured as a function of ion energy. Results are discussed from the standpoint of the adiabatic theory, and general agreement with the theory is noted. The mechanism responsible for production of Lyman alpha in the He(+) -H2 impact is identified as a dissociative charge exchange to an excited state. Reasons are set forth which show that the total charge exchange between He(+) and H2 at the low energies is probably due to a sum of processes of the type measured here, i.e., dissociative charge exchange to excited states. This is in contrast to an earlier interpretation by Hasted who suggested that it is due to dissociative charge exchange to the 2p sigma sub u state, one yielding a proton and a ground state atom. The He(+) -H2 and H2(+) -He collisions are discussed from the standpoint of similarities between them. The probability was measured for obtaining countable ultraviolet radiation from the impact of H2(+) on a metal surface. The experimental value of 1/5000 photons/ion is high compared to Shekhtar's value of 5 x 10 to the -7th power calculated for neutralization of an ion at a metal surface by radiating the excess energy. (Author)

Descriptors :   *ULTRAVIOLET SPECTROSCOPY, ATOMS, DISSOCIATION, HELIUM, IONS

Distribution Statement : APPROVED FOR PUBLIC RELEASE