Structure dependent competition between multiphoton absorption and intramolecular energy redistribution in organomolybdenum compounds: state selective production of molybdenum atoms

We have measured one color multiphoton dissociation/ionization spectra (MPD/MPI) across the one photon region 23 809 to 28 735 cm−1 for a structurally homologous series of organomolybdenum molecules including: (η6-cycloheptatriene)Mo(CO)3, Mo(CO)6, and a variety of (η6-arene)Mo(CO)3-type molecules. The degree of observability of the 7DJ, 7P0J, and 7S3 Rydberg series is observed to be a function of: (1) the number of low frequency vibrations associated with the molecular precursor, and (2) the degree of localization of the cyclic ligand to metal bond. These Rydberg series are taken as a simple but sensitive probe of the production of ground state metal atoms. The efficiency for MPD production of 7S3 molybdenum atoms relative to (η6-benzene)Mo(CO)3 increases in the order 1:1.9:11 with addition of a methyl substituent and extending it to an ethyl group. These observations are qualitatively and quantitatively in good agreement with previously reported relative efficiencies of MPD/MPI of organochromium molecules to produce ground state chromium atoms.