ANGULAR-DISTRIBUTIONS FOR SINGLE-ELECTRON AND DOUBLE-ELECTRON CAPTUREIN SLOW C(4-NE COLLISIONS())

In an earlier experiment by H. Cederquist et al. [J. Phys. B 18, 3951 (1985)] an unusual Q-value distribution for true double-electron captu re was reported for 400-eV C4+-Ne collisions: strong population of rea ction channels resulting in Q values between 27 and 35 eV followed by weakly populated channels in the region 18-25 eV and then again a stro ng channel at Q=16 eV. The last channel is nearly degenerate in Q valu e with the dominant single-electron capture reaction. Here, we report measured angular distributions for scattered projectiles in single- an d double-electron capture at collision energies 0.6-1.0 keV. At 0.6 ke V both single- and double-electron capture exhibit strong forward peak s for Q approximately 16 eV. The intensity for the latter, but not the former, decreases drastically when the energy is raised to 1 keV. The energy dependence of the angular distribution for double-electron cap ture with Q > 20 eV can be qualitatively understood in simple terms; s ingle-electron captures to 2s and 2p orbitals, however, yield unexpect edly wide and structured angular distributions.