SPECTROSCOPY OF JET-COOLED ALY

Pulsed laser ablation of a 1:1 Al:Y alloy in the throat of a pulsed su personic beam of helium or argon has been used to produce jet-cooled d iatomic AlY for study by resonant two-photon ionization spectroscopy. A band system of AlY at 9500 cm(-1) has been rotationally analyzed as an Omega' = 0 <-- Omega'' = 0 transition, and this is thought to corre spond to a [9.5](3) Sigma(0)(-) <-- X(3) Sigma(0)(-), band system. The bond lengths of the ground and excited states are r(0)''(X(3) Sigma(0 )(-)) = 2.8728 +/- 0.0012 Angstrom and r(e)'([9.5](3) Sigma(0)(-)) = 2 .83 +/- 0.03 Angstrom, respectively. The chemical bonding in AlY is di scussed and compared with the bonding in its cation, AlY+, and in Al-2 .