Time-resolved investigation of the ν1 ro-vibrational Raman band of H2CO with fs-CARS
✍ Scribed by A. M. Walser; P. Beaud; P. P. Radi; M. Tulej; T. Gerber; G. Knopp
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 324 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0377-0486
- DOI
- 10.1002/jrs.1613
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✦ Synopsis
Abstract
The technique of femtosecond time‐resolved coherent anti‐Stokes scattering (fs‐CARS) is used to investigate the strongly perturbed ν~1~ ro‐vibrational Raman band of formaldehyde (H~2~CO). The time‐dependent signal is simulated using a ‘Watson‐’Hamiltonian in A‐type reduction and Raman theory for asymmetric rotors. The results are compared with the experimental data. The fs‐CARS method measures the evolution of the polarization in a molecular ensemble via superposition of many states and is sensitive to spectral irregularities or line shifts of the involved transitions. ‘Coriolis’ interactions play a major role in the analysis of the ν~1~ band of formaldehyde. We successfully simulate the fs‐CARS transient signal from the ν~1~ band of formaldehyde including a model for multiple ‘Coriolis’ interactions, without the necessity of describing the complete interaction between all the vibrational levels. ‘Coriolis’ coupling coefficients and energy shifts are derived from the experiment by a least‐square fit. The results are discussed and compared to literature values. Copyright © 2006 John Wiley & Sons, Ltd.