34 research outputs found
Geminate recombination dynamics studied via electron reexcitation: Kinetic analysis for anion CTTS photosystems
Recently, it became practicable to study geminate recombination dynamics of
solvated electrons in polar liquids by using short pulses of light to reexcite
these electrons back into the conduction band of the liquid and observe a
change in the fraction of electrons that escape geminate recombination. In this
Letter, the potential of this technique to provide additional insight into the
recombination dynamics of electrons generated by charge-transfer-to-solvent
(CTTS) photodetachment from monovalent anions in polar liquids is studied
theoretically. The resulting expression accounts for the recent results from
B.J. Schwartz's group at UCLA for electron photodetachment from Na- in
tetrahydrofuran.Comment: 12 pages, 1 figure; to be submitted to Chem. Phys. Let
Geminate recombination of electrons generated by above-the-gap (12.4 eV) photoionization of liquid water
The picosecond geminate recombination kinetics for hydrated electrons
generated by 200 nm two photon absorption (12.4 eV total energy) has been
measured in both light and heavy water. The geminate kinetics are observed to
be almost identical in both H2O and D2O. Kinetic analysis based upon the
independent reaction time approximation indicates that the average separation
between the electron and its geminate partners in D2O is 13% narrower than in
H2O (2.1 nm vs. 2.4 nm). These observations suggest that, even at this high
ionization energy, autoionization of water competes with direct ionization.Comment: 10 pages + 2 figures, submitted to Chem. Phys. Letter
Elucidating the initial dynamics of electron photodetachment from atoms in liquids using variably-time-delayed resonant multiphoton ionization
We study the photodetachment of electrons from sodium anions in room temperature liquid tetrahydrofuran (THF) using a new type of three-pulse pump-probe spectroscopy. Our experiments use two variably-time-delayed pulses for excitation in what is essentially a resonant 1+1 two-photon ionization: By varying the arrival time of the second excitation pulse, we can directly observe how solvent motions stabilize and trap the excited electron prior to electron detachment. Moreover, by varying the arrival times of the ionization (excitation) and probe pulses, we also can determine the fate of the photoionized electrons and the distance they are ejected from their parent Na atoms. We find that as solvent reorganization proceeds, the second excitation pulse becomes less effective at achieving photoionization, and that the solvent motions that stabilize the excited electron following the first excitation pulse occur over a time of similar to450 fs. We also find that there is no spectroscopic evidence for significant solvent relaxation after detachment of the electron is complete. In combination with the results of previous experiments and molecular dynamics simulations, the data provide new insight into the role of the solvent in solution-phase electron detachment and charge-transfer-to-solvent reactions. (C) 2004 American Institute of Physics