Magnetic-sublevel differential cross sections for electron-impact excitation of He n1P levels: Theory and experiment in natural and atomic coordinate frames

Experimental data for the average transferred angular momentum, 〈_⊥〉, have been combined with experimental differential cross section DCS] data for electron impact excitation of the 2¹ P and 3¹ P levels of helium to obtain the individual magnetic-sublevel differential cross-sections, DCS _M ⁿ ], in the natural (and atomic) coordinate system. First-order many-body theory (FOMBT) has been used to obtain corresponding theoretical predictions for DCS _M ⁿ which are compared to these results. This comparison shows that FOMBT generally predictsM=+1 sublevel excitation DCS better than that forM=?1.