SPIN-POLARIZED ALKALI CLUSTERS - OBSERVATION OF QUARTET STATES OF THESODIUM TRIMER

Using helium cluster-isolation spectroscopy we have prepared and chara cterized the lowest quartet state (1(4)A'(2)) of the sodium trimer. Up on excitation to the 2(4)E' electronic state, laser induced fluorescen ce excitation and emission spectra have been obtained. With the aid of ab initio calculations, the spectra have been vibronically assigned a nd new insights on the nonadditivity of van der Waals interactions hav e been obtained. It is found that approximately 80% of the interaction energy in the 1(4)A'(2) state of Na-3 is due to nonadditive effects.