Calculation of electron scattering from tin atoms*

The relativistic convergent close-coupling (RCCC) method has been applied to study electron scattering from the atomic tin. Tin is of interest in fusion research as it may be used to monitor the erosion of fusion reactor wall tiles. It is also of interest to the nano-lithography industry, particularly with respect to the production of extreme ultra-violet light (EUV) which is generated using a plasma of tin ions. Both these applications require comprehensive collision data sets to allow accurate modelling of plasmas involving tin. We obtained integrated and momentum transfer cross sections for elastic scattering alongside integrated and differential cross sections for excitations to the 5p², 5p6s, 5p5d and 5p6p manifolds from the ground and first four excited states for projectile energies ranging from 0.1 to 500 eV. Total ionisation cross sections were obtained for the ground and first four excited states, including contributions from direct ionisation of the valence 5p shell and the closed 5s shell, and contribution from excitation auto-ionization. The tin atom is described by a model with two 5p-electrons above a frozen [Kr]4d¹⁰5s² core. Phenomenological one- and two-electron polarization potentials were used to best fit the calculated energy levels and optical oscillator strengths to experiment. Convergence was tested using several models with the number of target states included in the calculations varying from 33 to 399. For total ionisation cross sections, we find good agreement with experiment and other theories while for excitation cross sections the agreement is mixed.