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Time-dependent pump-probe spectra of NeBr2.
Jose A Cabrera1, Craig R Bieler, Benjamin C Olbricht
1Department of Chemistry and Institute of Surface and Interface Science, University of California, Irvine, California 92697-2025, USA. jcabrera@uci.edu
The Journal of Chemical Physics
|August 20, 2005
Summary
Investigating NeBr2 fragmentation dynamics reveals deviations from the energy-gap law for vibrational predissociation. Lifetimes plateau at 10-20 ps, indicating a shift in relaxation mechanisms at higher vibrational levels.
Area of Science:
- Chemical Physics
- Molecular Dynamics
- Spectroscopy
Background:
- NeBr2 fragmentation dynamics on the B electronic state are complex.
- Understanding vibrational predissociation and intramolecular vibrational relaxation is crucial.
Purpose of the Study:
- Characterize NeBr2 fragmentation dynamics on the B electronic state.
- Investigate the transition from direct vibrational predissociation to intramolecular vibrational relaxation.
- Determine Ne-Br2 bond energy in the E state.
Main Methods:
- Time- and frequency-resolved pump-probe spectroscopy.
- Utilized a novel Nd:yttrium aluminum garnet pumped dual optical parametric oscillator/optical parametric amplifier system.
- Achieved 2-cm(-1) spectral and 15-ps time resolution.
Main Results:
- Observed a deviation from the energy-gap law above nu'=20 for the Br2 stretching mode, with lifetimes leveling off between 10-20 ps.
- Determined the Ne-Br2 bond energy in the E state to be 82 cm(-1) via B-->E transitions.
- Noted increased lifetimes for vibrational levels nu'=27-29 due to the closing of the delta nu=-1 channel.
Conclusions:
- The fragmentation dynamics of NeBr2 exhibit a transition in relaxation mechanisms at higher vibrational energies.
- The developed spectroscopic system enables precise characterization of molecular fragmentation processes.
- Results provide insights into energy dissipation pathways in weakly bound molecular complexes.