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 ⁷D_J, ⁷P _J⁰, 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.