Absolute cross sections for near-threshold electron-impact excitation of the3s21S→3s3p1Pand3s21S→3s3p3Ptransitions inSi2+

Abstract

Absolute total cross sections for electron-impact excitation of the 3s{sup 2}{sup 1}S{r_arrow}3s3p{sup 3}P and 3s{sup 2}{sup 1}S{r_arrow}3s3p{sup 1}P transitions in Si{sup 2+} were measured using the merged electron-ion beams energy-loss technique. The results are compared to R-matrix close-coupling theory, which predicts a strong resonance enhancement of the cross section near the threshold for excitation of the {sup 3}P state and this is confirmed by the experiments. The observed disagreement between theory and experiment for the dipole excitation is suggested to be due to resonance interference. {copyright} {ital 1997} {ital The American Physical Society}