PHOTODISSOCIATION SPECTROSCOPY OF MG+-CO2

Mg+-CO2 ion-molecule complexes are produced in a pulsed supersonic nozzle cluster source, These weakly bound complexes are mass-selected and studied with laser photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer system. An electronic transition assigned as 2-pi <-- X 2-SIGMA+ is observed with an origin at 29625 cm-1 (vac). The spectrum is characterized by a six-member progression in the metal-CO2 stretching mode with a frequency (omega(e)') of 381.8 cm -1. An extrapolation of this progression fixes the excited state dissociation energy (D0') at 11 194 cm-1. The corresponding ground state value (D0" ) is 5150 cm-1 ( 14.7 kcal/mol). The 2-Pi-1/2,3/2 spin-orbit splitting is 56 cm-1. These studies were guided by ab initio calculations by Bauschlicher and co-workers, which provide accurate predictions of the electronic transition energy, vibrational constants and dissociation energy.