A random phase approximation study of the absorption spectrum of Na 8

Abstract

The electronic excitation energies for the Na 8 T d cluster and the associated oscillator strengths have been determined by effective core potential (ECP) calculations in the random phase approximation. A total of 20 allowed optical transitions have been computed; 1T 2and 2T 2 states correspond to the weak experimental transitions at 1.70 and 2.10 eV, whereas the overlap of transitions to 3T 2 and 4T 2 states accounts for the very intense experimental absorption band at 2.51 eV. The results agree with recent ECP configuration interaction computations and enlighten important discrepancies with results obtained within the spherical jellium local spin density RPA approximation. Excited-state properties and computed oscillator strengths are rationalized in terms of rearrangement and transition densities.