AN ABINITIO CONFIGURATION-INTERACTION STUDY OF THE EXCITED-STATES OF THE NA4 CLUSTER - ASSIGNMENT OF THE ABSORPTION-SPECTRUM

The vertical spectra for excited states of the Na4 cluster in its rhombus geometry and in its distorted tetrahedron geometry have been determined by ab initio large-scale CI methods. The excitation energies of optically allowed states for the rhombic structure are in good agreement with the spectroscopic transitions obtained from optical response experiments. The results are used to make structural and electronic assignment to those spectra. The nature of the interaction among alkali metal atoms in the ground and excited states of sodium tetramers has been characterized according to the leading features of the correlated wavefunctions. © 1990.