STRUCTURE DEPENDENT COMPETITION BETWEEN MULTIPHOTON ABSORPTION AND INTRAMOLECULAR ENERGY REDISTRIBUTION IN ORGANOMOLYBDENUM COMPOUNDS: STATE SELECTIVE PRODUCTION OF MOLYBDENUM ATOMS
Loading...
Date
1987
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
We have measured one color multiphoton dissociation/ionization (MPD/MPI) spectra for a series of arene molybdenum tricarbonyls. These experiments measure the relative timescales of multiphoton excitation, intramolecular energy redistribution (IER) and unimolecular dissociation under collision free conditions. Our organometallic MPD/MPI experiments involve focusing a tunable UV-visible laser pulse into a bulk gas sample and recording the total ion yield as a function of laser photon wavenumber. The directly observable spectral features reflect the distribution of metal atom states which is produced by the various dissociation processes that are simultaneously occuring. By studying a series of organometallic molecules whose structures were chosen to give systematic variation of intramolecular couplings and state densities and thus IER rates/paths, we strive to discover how the structure of a particular molecule determines the distribution of metal atom states formed when the ligands are removed by MPD. We concentrate on the production of ground state metal atoms by MPD from the organomolybdenum precursors. From our spectra, an even-parity $^{7}S_{3}$ Rydberg series of molybdenum was identified. Members of the analogous $^{7}D_{1,2,3,4,5}$ series can also be observed. Both of these series have the molybdenum atom ground state as the lower state in each transition. As such, their visibility is a direct indication of the extent of production and ionization of ground state molybdenum atoms by MPD of the parent molecule. As our results from the study of organochromium compounds suggest, ground state atom production is favored when the ligands are strongly bound to the metal atom and when the ligands have structures that induce the existence of low frequency vibrational modes. Both of these factors tend to facilitate the transfer of internal energy from the metal atom to the ligands.
Description
Author Institution: Department of Chemistry, Syracuse University