CALCULATED CROSS-SECTIONS FOR ELECTRON-CAPTURE BY PROTONS FROM HELIUM INTO THE H(N = 3) LEVEL

Cross sections have been computed for electron capture by protons from helium atoms in the range of projectile energies 20<or=E<or=150 keV. The semiclassical impact parameter method was employed, using a basis of travelling atomic orbitals on both nuclei. Exchange effects, arising from the identity of the two electrons, have been incorporated, and their importance is assessed. The theoretical results are compared with recent measurements of density matrix elements for capture into the n=3 states of hydrogen. © 1990 IOP Publishing Ltd.