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Fully and partially coherent pathways in multiply enhanced odd-order wave-mixing spectroscopy
Nathan A Mathew1, Lena A Yurs, Stephen B Block
1Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
The Journal of Physical Chemistry. A
|December 3, 2009
Summary
Coherent multidimensional spectroscopy (CMDS) advances chemical measurements by creating higher-order coherences. This study demonstrates a new method, multiply enhanced odd-order wave-mixing (MEOW), to achieve this, revealing detailed molecular vibrational states.
Area of Science:
- Chemical Physics
- Spectroscopy
- Quantum Coherence
Background:
- Nuclear magnetic resonance (NMR) spectroscopy utilizes multiple excitation pulses for chemical specificity via multiple quantum coherences.
- Coherent multidimensional spectroscopy (CMDS) is the optical analog of NMR, currently employing three pulses to generate low-order coherences.
- Generating higher-order coherences in CMDS requires higher excitation intensities, leading to complex coherence pathways.
Purpose of the Study:
- To introduce and characterize multiply enhanced odd-order wave-mixing (MEOW) as a method for generating higher-order multiple quantum coherences in CMDS.
- To investigate the role of dynamic Stark effects in high-intensity CMDS.
- To demonstrate the utility of MEOW for detailed molecular state analysis using a rhodium dicarbonyl chelate (RDC) model.
Main Methods:
- Implementation of high-intensity laser excitation in CMDS to achieve Rabi frequencies comparable to dephasing rates.
- Utilizing phase matching conditions at high intensities, which allows for multiple coherence pathways, including those influenced by dynamic Stark effects.
- Acquiring a series of 2D spectra by varying excitation frequencies and pulse delays to probe multidimensional parameter space.
Main Results:
- MEOW methods were shown to create multiple, odd-order coherence pathways, including partially and fully coherent pathways.
- Dynamic Stark effects were observed to excite vibrational ladders up to v=6 in the RDC model.
- Analysis of the spectra enabled the identification of 18 distinct overtone and combination band states, showing excellent agreement with a local mode model.
Conclusions:
- Multiply enhanced odd-order wave-mixing (MEOW) provides a pathway to generate higher-order multiple quantum coherences in CMDS, analogous to advanced NMR techniques.
- The study highlights the significant influence of dynamic Stark effects at high excitation intensities in CMDS.
- MEOW, combined with spectral analysis, offers a powerful tool for detailed characterization of molecular vibrational states and couplings.
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