PHOTODISSOCIATION SPECTROSCOPY OF MG+-H2O

Mg+-H2O 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 2B2-->X2A1 is observed with an origin at 28399 cm-1 (vac). The spectrum has a prominent progression in the metal-H2O stretching mode with a frequency (omega(e)') of 517.1 cm-1. An extrapolation of this progression fixes the excited state dissociation energy (D0') at 16008 cm-1. The corresponding ground state value (D(0)") is 8732 cm-1 (25.0 kcal/mol). The solvated bending mode and asymmetric stretching mode of water are also active in the complex. A second electronic transition assigned as 2B1<--X2A1 is observed with an origin at 30386 cm-1 and a metal stretch frequency of 483.4 cm-1. This study was guided by ab initio calculations by Bauschlicher and co-workers, which provide accurate predictions of the electronic transition energies, vibrational constants and dissociation energies.