Photodissociation spectroscopy of the Mg+-C2H2 pi-complex

The Mg+-acetylene complex is produced by pulsed-nozzle laser vaporization a nd studied with mass-selected resonance-enhanced photodissociation spectros copy. A progression of broad vibrational bands is observed near 347 nm. The broad linewidths, which preclude rotational resolution, are attributed to rapid predissociation in the excited state. The progression is assigned to the metal-acetylene stretch in the B-2(1) <-- X(2)A(1) band system, which p roduces vibrational constants of omega'(epsilon) = 330.5 cm(-1) and D'(0) = 13100 cm(-1). The ground-state dissociation energy is estimated as D "(0) = 6100 cm(-1) (17.4 kcal mol(-1)). These properties are in good agreement w ith the predictions of theory. (C) 1999 Elsevier Science B.V. All rights re served.