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, O-el, total ionization, Q(ion), and total (complete), Q(T), 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 (Q(el)) and its inelastic counterpart (Q(inel)). The sum of Q(el) and Q(inel) gives the total (complete) cross-section, Q(T), 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. Qin,' includes (Ion and we have developed a semi-empirical method, called complex scattering potential-ionization contribution (CSP-ic) to extract ionization crosssections 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. (C) 2010 Elsevier B.V. Al! rights reserved.