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Spectral Signatures of Ground- and Excited-State Wavepacket Interference after Impulsive Excitation
Colin Fitzpatrick1, Johanan H Odhner1, Robert J Levis1
1Center for Advanced Photonics Research, Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States.
The Journal of Physical Chemistry. A
|August 14, 2020
Summary
Impulsive transient absorption spectroscopy reveals how vibrational coherences form in cresyl violet perchlorate. Simultaneous excitation creates wavepacket interference, impacting data interpretation.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Vibrational coherences play a crucial role in ultrafast molecular dynamics.
- Understanding wavepacket evolution is key to controlling photochemical reactions.
- Cresyl violet perchlorate is a model chromophore for studying excited-state dynamics.
Purpose of the Study:
- To investigate the formation and evolution of vibrational coherences in cresyl violet perchlorate.
- To differentiate between ground- (S0) and excited- (S1) state wavepacket dynamics.
- To analyze the effects of different excitation conditions on wavepacket formation and interference.
Main Methods:
- Impulsive transient absorption spectroscopy was employed.
- Resonant, off-resonant, partially resonant, and broadband excitation conditions were utilized.
- Wavepacket filtering using windowed Fourier transforms was applied for analysis.
Main Results:
- Selective formation of S0 and S1 wavepackets was achieved under different excitation conditions.
- Simultaneous excitation led to wavepacket interference on a picosecond timescale.
- Observed interference effects included shifting phase-flips and zero-amplitude nodes.
- Raman features showed a red shift of 2-10 cm⁻¹ for excited-state wavepackets.
Conclusions:
- Excitation conditions dictate the selective or simultaneous formation of ground and excited-state wavepackets.
- Interference between simultaneously excited wavepackets produces unique spectral features.
- Careful data interpretation is necessary, especially when using wavepacket filtering techniques.
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