THEORETICAL INTERPRETATION OF THE PHOTOELECTRON DETACHMENT SPECTRA OF NA-2-5(-) AND OF THE ABSORPTION-SPECTRA OF NA3, NA4, AND NA8 CLUSTERS

The configuration-interaction (CI) study of excited states of alkali metal clusters accounts for spectroscopical patterns obtained from (i) the photoelectron detachment spectra of their anions and from (ii) the photodepletion spectra of the neutral species, reproduces observed excitation energies, intensities for allowed transitions, and permits an assignment of cluster structures. For Na2-4- the linear anionic geometries are responsible for the photoelectron detachment spectra. In the case of Na5-, both planar and linear anionic isomers seem to contribute to the recorded spectrum. The calculation of optically allowed states for Na3(C2υ ) and Na4(D2h) structures and oscillator strengths yield rich spectra which have been fully assigned to the observed ones. In the case of Na8, the Td and the related D2d forms give rise to an intense transition located at ∼495 nm and the weak fine structure shifted to the red in full agreement with the measured spectrum. A molecular versus collective excitation interpretation of absorption spectra is discussed. © 1990 American Institute of Physics.