Electron capture cross-sections between 3He+ ion and rubidium vapor in the energy range 1.0–19 keV

Electron capture cross-sections have been measured for 3He+ ions in Rb vapor. The deduced data were used for evaluating the performance of the proposed polarized 3He ion source (SEPIS) based on the spin-exchange collisions. Measurements of the 3He+ beam components after passing through the target were made as a function of the Rb target thickness at energies ranging from 1.0 to 19 keV. The Rb vapor thickness was varied by changing the Rb cell temperature and the thicknesses were calibrated by observing the Faraday rotation angles of a probe laser (λ=782.0nm) penetrating the Rb vapor under the presence of a magnetic field (∼0.26T). Assuming that the double electron capture and stripping of 3He0 atoms are neglected, the electron capture cross-sections σcσc were deduced. It was found that the observed energy dependence of σcσc significantly deviated from that of the He+4+Cs system which was measured in the past.Lastly, the observed energy dependence of σcσc was compared with the theoretical calculation assuming the semi-classical close-coupling method based on the molecular-orbital expansion. It was found that the calculated results, as a whole, reproduced the experimental results except for the data collected at 1 keV. This qualitative reproduction partly supports the appropriateness of the above theory which predicts the large spin-exchange cross-sections at low energies.