title: Protoheme-carbon monoxide geminate kinetics.
abstract: Recombination kinetics of CO to protoheme after laser photolysis have been measured vs. temperature and viscosity. A 25-ns laser pulse was focused on the sample to produce an excitation rate of 10(9)/s per heme. This temporarily populates the heme-CO state of dissociated pairs which either separate or recombine on a picosecond time scale in viscous glycerol-water solutions. From the equilibrium amplitude of the fraction dissociated during the laser pulse, the geminate recombination rate constant is calculated to be 3 X 10(9)/s. This rate coefficient is only weakly dependent on temperature or viscosity. As previously observed the fraction that escapes depends on the solvent viscosity [Marden, M. C. (1983) Ph.D. Thesis, University of Illinois-Urbana]. A model consisting of a single barrier plus diffusive escape is used to simulate the kinetics during and just after the flash.
mesh_terms: D002248:Carbon Monoxide; D019855:Ethylene Glycol; D005026:Ethylene Glycols; D005990:Glycerol; D006418:Heme; D007700:Kinetics; D007834:Lasers; D008433:Mathematics; D008954:Models, Biological; D010782:Photolysis
chemical_list: D005026:Ethylene Glycols; D006418:Heme; D002248:Carbon Monoxide; D019855:Ethylene Glycol; D005990:Glycerol