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

Abstract

In this article we report calculations of the total elastic, Q 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. Q inel includes Q ion 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.