RELATIVISTIC R-MATRIX CALCULATIONS FOR ELECTRON ALKALI-METAL-ATOM SCATTERING - CS AS A TEST CASE

We have reformulated the Dirac R-matrix method for low-energy electron scattering by (effectively) one-electron, alkali-metal-like systems and developed an independent computer program for this special purpose. A highly accurate and relativistic representation of the target was used to perform a multichannel close-coupling calculation of cross sections for electron scattering. Our results include the negative-ion affinity and elastic, inelastic, and total cross sections for incident electrons with 0 to 2.8 eV kinetic energy. We find that core-polarization and relativistic effects lead to multiplets of very narrow P-3(J), J = 0, 1, 2 shape resonances: the effect of the induced core polarization on the electron-electron correlation leads to 6s6p P-3(J)o resonances in contrast to previously predicted bound states of Cs-, and relativistic interactions are responsible for the autoionizing decay of 6p2 P-3(J) states below the first excitation threshold.