Excited state dynamics of liquid water: Insight from the dissociation reaction following two-photon excitation

Journal Article · Sat Apr 28 04:00:00 EDT 2007 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2727468· OSTI ID:20991257

Elles, Christopher G; Shkrob, Ilya A; Crowell, Robert A; Bradforth, Stephen E ^[1]

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1. Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

The authors use transient absorption spectroscopy to monitor the ionization and dissociation products following two-photon excitation of pure liquid water. The primary decay mechanism changes from dissociation at an excitation energy of 8.3 eV to ionization at 12.4 eV. The two channels occur with similar yield for an excitation energy of 9.3 eV. For the lowest excitation energy, the transient absorption at 267 nm probes the geminate recombination kinetics of the H and OH fragments, providing a window on the dissociation dynamics. Modeling the OH geminate recombination indicates that the dissociating H atoms have enough kinetic energy to escape the solvent cage and one or two additional solvent shells. The average initial separation of H and OH fragments is 0.7{+-}0.2 nm. Our observation suggests that the hydrogen bonding environment does not prevent direct dissociation of an O-H bond in the excited state. We discuss the implications of our measurement for the excited state dynamics of liquid water and explore the role of those dynamics in the ionization mechanism at low excitation energies.

• OSTI ID: 20991257
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 16 Vol. 126; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
DISSOCIATION
DISSOCIATION ENERGY
EV RANGE 01-10
EV RANGE 10-100
EXCITATION
EXCITED STATES
KINETIC ENERGY
LIQUIDS
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
PHOTOLYSIS
PHOTONS
REACTION KINETICS
SIMULATION
WATER