Scattering of electrons by Ca, Sr, Ba and Yb atoms in the 0-200 eV energy region in the optical potential model

A phenomenological complex optical potential is used to investigate the elastic and inelastic scattering of electrons by Ca, Sr, Ba and Yb atoms in the energy range E<or=200 eV. The values of adjustable parameters in the polarization potential were found using known electron affinity to the Ca, Sr, Ba and Yb atoms. It is also shown that peaks near elastic thresholds in cross sections, which have been found in experiments, arise from 2D shape resonances at energies equal to 0.87 eV, 0.60 eV, 0.34 eV and 0.89 eV and with widths equal to 0.98 eV, 0.68 eV, 0.13 eV and 0.89 eV for Ca, Sr, Ba and Yb, respectively. Comparisons with experimental data and other theoretical results are given.