ISOMERS AND TRANSITION-STATES OF THE NA-4(- AB-INITIO STUDIES OF GEOMETRIES AND ABSORPTION-SPECTRA() CLUSTERS )

Stable isomers, transition states, and their photoabsorption spectra f or the Na-4(+) cluster are determined by ab initio MRCI calculations. Three stable geometries of symmetry C-2v, D-2h, and D-2d and two trans ition states of symmetry C-s and C-2 are identified. The D-2d configur ation is a new geometry not previously obtained in ab initio calculati ons. The photoabsorption spectra of the three isomers and the transiti on states are used to interpret experimental absorption data. Dissocia tion dynamics and possible laser control of isomer populations are dis cussed in terms of the electronic states of the cluster.