Ionization-excitation magnetic sublevel cross sections for He+ (2p)2P0 states following fast electron and proton impact

The first experimental magnetic substate scattering-angle-integrated cross sections following ionization-excitation of He(1s(2))S-1 to He-(2p) P-2(0) in the e(-) + He collision system have been determined using a combination of total cross sections and polarization fraction measurements in the extreme ultraviolet range. The derived magnetic sublevel cross sections, sigma(0) and sigma(1), for M-L = 0, +/-1 have been studied over a wide range of electron velocities (2-8.5 a.u.). These results are compared with previous cross sections for equi-velocity proton impact. In addition, our experimental data are compared with earlier theoretical predictions, our recent second-Born calculations fully including off-energy shell terms, and new R-matrix results. We have extended our polarization measurements for H+ + He collisions and found excellent agreement between theory and experiment at nearly all impact energies. However, the present second-Born and R-matrix results deviate slightly from the experimental electron data. (C) 2003 Elsevier Science B.V. All rights reserved.