Ionization–excitation of helium to He+(2p)magnetic sublevels following electron, proton, and molecular hydrogen (H2+ andH3+)impact

Abstract

Experimental magnetic sublevel scattering-angle-integrated cross sections followingionization–excitation of He(1s2)1S to He+(2p)2Po ine− + Heand Hm+ + He (m = 1–3)collision systems have been determined using a combination of totalcross sections and polarization fraction measurements in the extremeultraviolet range. The derived magnetic sublevel cross sections, σ0 and σ1, for ML = 0 +/- 1have been studied over a wide range of velocities (2–8.5 au) for electron impact onhelium. These results are compared with previous experimental proton crosssections (2–6 au) as well as new measured data for hydrogen molecularimpact (1.4–4.0 au) for equi-velocity. In addition, our electron and protonmeasurements are compared with earlier theoretical predictions, our recentsecond-Born calculations fully including off-shell energy terms, and presentpredictions from a hybrid first-order and second-order distorted-wave plusR-matrix (close-coupling) model(DWB1 + RMPS andDWB2 + RMPS).Finally, we have extended our polarization measurements for H+ + Hecollisions and found excellent agreement between theory and experiment at nearlyall impact energies. However, the present second-Born and DWB1 + RMPSresults deviate slightly from the experimental electron data while the DWB2 + RMPScalculations tend toward the experimental data of Forand et al (1985 J. Phys. B:At. Mol. Phys. 18 1409).