ABSOLUTE RATE CONSTANTS OF MO-2-(X-(1)SIGMA(-(A-S-7(3)) WITH O-2 AT ROOM-TEMPERATURE()(G)) AND MO)

The gas phase reactivities of ground-state molybdenum dimers and atoms for oxygen molecule have been investigated in a mass-flow controlled cell. Transient concentration of Mo-2 (X(1) Sigma(g)(+), nu = 0) or Mo (a(7)S(3)) produced by 355 nm multiphoton dissociation (MPD) of Mo(CO )(6) was monitored by a laser-induced fluorescence (LIF). The predicta ble disturbance caused by free electrons inevitably produced in the MP D of metal carbonyls was examined by an appropriate addition of SF6 as an electron scavenger. The pseudo-first order decay rates of these mo lybdenum species were found to depend linearly on O-2 pressure both in the absence and in the presence of SF6, giving the bimolecular rate c onstants of (1.1 +/- 0.1) x 10(-11) for Mo-2 (X(1) Sigma(g)(+), nu = 0 ) + O-2 and (1.2 +/- 0.1) x 10(-10) cm(3) molecule(-1) s(-1) for Mo (a (7)S(3)) + O-2 under the 6.5 Torr total pressure with balance Ar at ro om temperature.