1^st International Laser M2P Conference

J. Phys. Colloques 48 (1987) C7-591-C7-593
DOI: 10.1051/jphyscol:19877144

LASER SPECTROSCOPY OF METAL CLUSTERS

M. BROYER¹, G. DELACRÉTAZ², P. LABASTIE³, R. L. WHETTEN⁴, J. P. WOLF² and L. WÖSTE<sup>2

1</sup>  Laboratoire de Spectrométrie Ionique et Moléculaire CNRS LA-171, Université Lyon I, Bâtiment 205, 43, Bd du 11 novembre 1918, F-69622 Villeurbanne Cedex, France
²  Institut de Physique Expérimentale, Ecole Polytechnique Fédérale de Lausanne. PHB-Ecublens, CH-1015 Lausanne, Switzerland
³  Laboratoire de Spectrométrie Ionique et Moléculaire CNRS LA-171, Université Lyon 1, Bâtiment 205, 43, Bd du 11 novembre 1918, F-69622 Villeurbanne Cedex, France
⁴  Department of Chemistry and Biochemistry, Solid State Science Center, University of California, Los Angeles, CA 90024, U.S.A.

Abstract
Conventional spectroscopy are not easily applied to clusters systems, because these parlicules are generally produced in size distributions in molecular beams. The two-photon ionization spectroscopy has been demonstrated to be an efficient method to select a particular size. Results are available in the literature on Na₃ [1] and Cu₃ [2]. Recently the depletion spectroscopy [2,3] has been used to investigate predissociated states : an ultraviolet laser directly ionizes the cluster and monitors the remaining population in the molecular beam. Whenever a predissociated level is simultaneously excited by the exciting laser, a depletion of the ion cluster intensity is observed. By this method a completely predissociated highly excited state of Na₃ (the D state) has been recently observed [3]. The depletion experiment has been used to probe all the other known states of Na₃ (A, B, B' and C states). No evidence of predissociation has been found for the A, B, B' states while the C state appears strongly predissociated except the two first bands. Figure 1 shows the comparison between the two-photon ionization and the depletion spectra in the C state. The whole spectrum observed by depletion allows us to determine the symmetry of the C state (²E") and to assigne all the bands by solving the Jahn-Teller hamiltonian.