Time-resolved study of solvent-induced recombination in photodissociated IBr{sup -}(CO{sub 2}){sub n} clusters
- JILA, University of Colorado, Boulder, Colorado 80309 and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)
We report the time-resolved recombination of photodissociated IBr{sup -}(CO{sub 2}){sub n} (n=5-10) clusters following excitation to the dissociative IBr{sup -}A{sup '} {sup 2}{pi}{sub 1/2} state of the chromophore via a 180 fs, 795 nm laser pulse. Dissociation from the A{sup '} state of the bare anion results in I{sup -} and Br products. Upon solvation with CO{sub 2}, the IBr{sup -} chromophore regains near-IR absorption only after recombination and vibrational relaxation on the ground electronic state. The recombination time was determined by using a delayed femtosecond probe laser, at the same wavelength as the pump, and detecting ionic photoproducts of the recombined IBr{sup -} cluster ions. In sharp contrast to previous studies involving solvated I{sub 2}{sup -}, the observed recombination times for IBr{sup -}(CO{sub 2}){sub n} increase dramatically with increasing cluster size, from 12 ps for n=5 to 900 ps for n=8,10. The nanosecond recombination times are especially surprising in that the overall recombination probability for these cluster ions is unity. Over the range of 5-10 solvent molecules, calculations show that the solvent is very asymmetrically distributed, localized around the Br end of the IBr{sup -} chromophore. It is proposed that this asymmetric solvation delays the recombination of the dissociating IBr{sup -}, in part through a solvent-induced well in the A{sup '} state that (for n=8,10) traps the evolving complex. Extensive electronic structure calculations and nonadiabatic molecular dynamics simulations provide a framework to understand this unexpected behavior.
- OSTI ID:
- 20864310
- Journal Information:
- Journal of Chemical Physics, Vol. 125, Issue 13; Other Information: DOI: 10.1063/1.2217741; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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