OPTICAL-ABSORPTION PROBES OF LIXNA4-X(X=1,2) - GEOMETRY, SUBSTITUTIONISOMERS, AND COMPOSITION-DEPENDENT ELECTRON DELOCALIZATION

Photodepletion spectra (415-763 nm, 10 angstrom effective resolution) were obtained for LiNa3 and Li2 Na2 and compared to previous Na4 and L i4 measurements as well as to model calculations ranging from classica l electrostatic to ab initio molecular orbital. Findings include (i) t he assignment of planar rhombic singlet ground states for both molecul es; (ii) in Li2 Na2, the possible observation of predominantly one of three energetically close-lying planar rhombic or near rhombic substit ution isomers; and (iii) in the sodium/lithium tetramer series, eviden ce for increasing localization of itinerant valence electrons with inc reasing cluster lithium content.