e+or-impact excitation of autoionising levels in alkalis: a distorted-wave approach

Distorted-wave calculations are performed for electron (and positron) impact excitation of lowest-lying autoionising levels in alkalis (Li, Na, K, Rb and Cs). Appropriate initial- and final-state static potentials have been used for distorting the incident and scattered projectile electron (and positron) waves, respectively. In the case of lithium the effect of the polarisation potential (in addition to static potentials) is also considered for the distorting potential of the projectile electron. Results for differential and total cross sections, anisotropy parameter ( beta ), polarisation fraction ( pi ) as well as for lambda and chi parameters are reported. Comparison of the present results with earlier available experimental and theoretical results is presented.