Simple method for Calculating Electron Affinity: Results for Ca, Sr and Ce

We have benchmarked the recently developed Regge-pole methodology for electron- atom elastic scattering on the most recent measurement of the electron affinity (EA) of the Ca atom [1]. The predictive power of the methodology is then demonstrated by calculating the binding energy of the ground state of the very complicated Ce$^-$ ion, with a g-orbital attachment, a shape resonance at 0.37 eV and a Ramsauer-Townsend minimum at about 0.09~eV [2]. Our calculated EA for Ce agrees very well with the latest measured value [3], but disagrees with that of Ref. [4]. Low-energy electron scattering partial, total and differential cross sections for e$^-$-Ca, e$^-$-Sr and e$^-$-Ce will be presented and discussed.\\ $[1]$ V. V. Petrunin, H. H. Andersen, P. Balling and T. Andersen, Phys. Rev. Lett. {\bf 76}, 744 (1996)\\ $[2]$ Z. Felfli, A. Z. Msezane and D. Sokolovski, J. Phys. B {\bf 41}, Fast Track,At Press (2008)\\ $[3]$ C. W. Walter {\it et al}, Phys. Rev. A {\bf 76}, 052702 (2007)\\ $[4]$ V. T. Davis and J. S. Thompson, Phys. Rev. Lett. {\bf 88}, 073003 (2002)