Calculations of total and ionization cross-sections on electron impact for alkali metals (Li, Na, K) from threshold to 2 keV

In this article we report calculations of the total elastic, Qel, total ionization, Qion, and total (complete), QT, cross-sections for the targets Li, Na, K having low ionization thresholds and high polarizability upon electron impact for energies from circa threshold to 2000 eV. We have employed the well-known spherical complex optical potential (SCOP) formalism, which provides total elastic cross-section (Qel) and its inelastic counterpart (Qinel). The sum of Qel and Qinel gives the total (complete) cross-section, QT, which is found to be very high at the lower energies (around 5 eV). This is attributed to high polarizabilities and low ionization thresholds of these atoms. Qinel includes Qion and we have developed a semi-empirical method, called complex scattering potential-ionization contribution (CSP-ic) to extract ionization cross-sections from calculated total inelastic cross-section. Present calculations also provide information on the total excitation processes of these targets. The calculated cross-sections are examined as functions of incident electron energy along with available comparison and overall good agreement is observed.

Graphical abstractWe report calculations of Qel, Qion and QT, cross-sections for Li, Na, K atoms upon electron impact for energies from threshold to 2000 eV. We have employed well-known SCOP and CSP-ic method formalism to compute Qel, Qinel and Qion. QT is very high at the lower energies. The figure compares the total ionization cross-section for e–Li scattering with available data. The present results are in very good accord with theoretical values of McFarland [9]. At peak the present results are slightly higher than results of McFarland [9]. The experimental results of McFarland and Kinney [7] and Brink [8] are also in very good accord with present data for the entire energy range.Figure optionsDownload full-size imageDownload high-quality image (142 K)Download as PowerPoint slide