Related Experiment Videos
Ultrafast dynamics for electron photodetachment from aqueous hydroxide
Robert A Crowell1, Rui Lian, Ilya A Shkrob
1Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. rob_crowell@anl.gov
The Journal of Chemical Physics
|July 23, 2004
Summary
Ultrafast laser spectroscopy reveals that biphotonic excitation of hydroxide ions yields more escaped electrons than monophotonic excitation. Temperature influences electron escape and recombination rates in aqueous solutions.
Area of Science:
- Physical Chemistry
- Photochemistry
- Spectroscopy
Background:
- Charge-transfer-to-solvent reactions are crucial in aqueous systems.
- Understanding electron dynamics after photoexcitation is key to photochemistry.
- Hydroxide ions play a significant role in various chemical processes.
Purpose of the Study:
- To investigate charge-transfer-to-solvent reactions of hydroxide ions.
- To study the kinetics of hydrated electrons generated by different excitation methods.
- To analyze the influence of hydroxide concentration and temperature on electron escape and recombination.
Main Methods:
- Pump-probe ultrafast laser spectroscopy was employed.
- Transient absorption kinetics of hydrated electrons (e(aq)(-)) were measured.
- Data were analyzed as a function of hydroxide concentration and temperature.
Main Results:
- Geminate decay kinetics of hydrated electrons are bimodal, featuring a fast component and a slower power-law tail.
- Biphotonic excitation resulted in a 1.8 times higher fraction of escaped electrons compared to monophotonic excitation.
- Electron escape fraction increased with temperature, with activation energies of 8.3 and 22.3 kJ/mol for recombination and dissociation, respectively.
Conclusions:
- Biphotonic excitation broadens the electron distribution, enhancing escape.
- Electron detachment via biphotonic excitation of hydroxide is inefficient.
- The study provides insights into the photoionization of water and reaction dynamics.