RelativisticR-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 ³{P}J$, J=0,1,2 shape resonances: the effect of the induced core polarization on the electron-electron correlation leads to 6s6${p}³PJᵒ resonances in contrast to previously predicted bound states of Cs^-, and relativistic interactions are responsible for the autoionizing decay of 6p² ³{P}J$ states below the first excitation threshold.