Eur. Phys. J. A (2006) 27: 181-185
https://doi.org/10.1140/epja/i2006-08-027-4

Nuclear Physics in Astrophysics II

Radiative and non-radiative electron capture from carbon atoms by relativistic helium ions

¹ The Andrzej Soltan Institute for Nuclear Studies, 05-400, Otwock - Świerk, Poland
² Department of Physics, Osaka University, 560-0043, Osaka, Japan
³ Research Center for Nuclear Physics, Osaka University, 567-0047, Osaka, Ibaraki, Japan
⁴ Laboratory of Applied Physics, Kyoto Prefectural University, 1 Hangicho, Shimogamo, Sakyo-ku, 606-8522, Kyoto, Japan
⁵ IPNS (Institute of Particle and Nuclear Studies), KEK (High Energy Accelerator Research Organization), Oho 1, 305-0801, Tsukuba, Ibaraki, Japan
⁶ Department of Physics, Nara Women's University, Kitauoya-nishimachi, 630-8506, Nara, Japan
⁷ Kyoto Prefectural University, 606-8522, Kyoto, Japan
⁸ Kobe Tokiwa Jr. College, 653-0824, Nagata, Kobe, Japan

Received: 11 July 2005
Accepted: 20 December 2005
Published online: 29 March 2006

Abstract

Interaction of radiation with helium atoms and/or ions is of interest in various astrophysical applications. The reverse reactions of fast 150MeV/amu ³He⁺⁺ ions with solid C targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The singly ionized helium ions resulting from capture of the target electrons to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at θ = 0^° with respect to the beam. The yield ratios of singly-to-doubly ionized helium ions emerging from thin carbon foils, He⁺/ He⁺⁺, have been measured as a function of the foil thickness. Extrapolating the results to zero target thickness permits to determine the cross section values separately for electron stripping from ³He⁺ ions and for electron capture to ³He⁺⁺ ions. The radiative and non-radiative contributions to the capture cross section were determined in a separate experiment in which the 84 keV (C.M.) photons were observed in coincidence with the He⁺ ejectiles. The results are compared with theoretical predictions. Need for improved calculations is noted for all the three processes involved, i.e. for the radiative and non radiative electron capture as well as for the electron stripping.