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Updated: Jun 18, 2026

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Femtosecond electron detachment of aqueous bromide studied by two and three pulse spectroscopy
Martin K Fischer1, Alfred Laubereau, Hristo Iglev
1Physik-Department E 11, Technische Universität München, D-85748 Garching, Germany.
Abstract:
The photodetachment of aqueous bromide after excitation at 202 nm is studied by pump-probe and pump-repump-probe spectroscopy. The initially excited charge-transfer-to-solvent state is followed by an intermediate assigned to non-equilibrated bromine-electron pairs. The subsequent dynamics are governed by equilibration, recombination and dissociation of the pairs, yielding the final hydrated electrons. An additional repump pulse is used for secondary excitation of the intermediate species, increasing the final number of hydrated electrons. Thus, a fraction of the solvent-separated bromine-electron pairs are converted to fully released electrons representing an optical manipulation of the photodetachment pathway. The observed hindrance of the recombination process by repumping allows determination of the effective lifetime of the solvent-separated atom-electron pairs to be 19 +/- 2 ps at room temperature. The measured temperature dependence of the time constant suggests a free energy barrier for pair dissociation of DeltaG = 0.15 +/- 0.02 eV.
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