Absolute rate constants of Mo2 (X1Σg+) and Mo (a7S3) with O2 at room temperature

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 Mo2 (X1Σg+, ν = 0) or Mo (a7S3) produced by 355 nm multiphoton dissociation (MPD) of Mo(CO)6 was monitored by a laser-induced fluorescence (LIF). The predictable disturbance caused by free electrons inevitably produced in the MPD of metal carbonyls was examined by an appropriate addition of SF6 as an electron scavenger. The pseudo-first order decay rates of these molybdenum species were found to depend linearly on O2 pressure both in the absence and in the presence of SF6, giving the bimolecular rate constants of (1.1 ± 0.1) × 10−11 for Mo2 (X1Σg+, ν = 0) + O2 and (1.2 ± 0.1) × 10−10 cm3 molecule−1 s−1 for Mo (a7S3) + O2 under the 6.5 Torr total pressure with balance Ar at room temperature.