Application of the finite-element-discrete-model method for calculating resonance properties

A enhanced procedure implementing the finite-element-discrete-model method [R. K. Nesbet, Phys. Rev. A 24,1184 (1981)] for determining atomic or molecular shape resonances and widths is described. The present procedure includes an approximation for the static exchange plus polarization model involving Moller-Plesset perturbation theory. Applications to Mg, N-2, CH2O, and uracil are described. Compared with experiment, the results for Mg are within 5 meV for the resonance position and 75 meV for the width. The vertical geometry results for N-2 and CH2O compare well with experiment insofar as can be determined in the presence of nuclear motion complications. Uracil is calculated as an example where the large dipole moment (4.8 D) has an impact on threshold properties and possible dipole bound states.