Presented as part of a commemorative issue for Wolfgang Kiefer on the occasion of his 65th birthday.
Quantitative polarization-sensitive resonance CARS and resonance Raman spectroscopy on octaethylporphine†
Article first published online: 12 JAN 2006
Copyright © 2006 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Special Issue: Commemorative Issue: for Wolfgang Kiefer on the Occasion of his 65th Birthday
Volume 37, Issue 1-3, pages 384–391, January - March 2006
How to Cite
Koster, J., Popp, J. and Schlücker, S. (2006), Quantitative polarization-sensitive resonance CARS and resonance Raman spectroscopy on octaethylporphine. J. Raman Spectrosc., 37: 384–391. doi: 10.1002/jrs.1439
- Issue published online: 12 JAN 2006
- Article first published online: 12 JAN 2006
- Manuscript Accepted: 15 JUN 2005
- Manuscript Received: 16 APR 2005
- German Research Foundation (Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 630, Teilprojekt C1).
- polarization-sensitive multiplex detection;
- resonance Raman spectroscopy;
- resonance CARS spectroscopy;
- free-base porphyrins;
- line shape analysis;
- coherent phases
We present polarization-sensitive (PS) multiplex coherent anti-Stokes Raman scattering (CARS) spectra of octaethylporphine (OEP) in solution employing Q band resonance conditions. Several advantages of this four-wave mixing technique compared with spontaneous resonance Raman (RR) spectroscopy are demonstrated. PS CARS spectroscopy allows the acquisition of high-quality polarized vibrational spectra of this luminescent D2h symmetric free-base porphyrin. From a quantitative CARS lineshape analysis, a set of accurate band parameters for the normal modes in the range 1510–1670 cm−1 is determined; in particular, individual spectral contributions from the nearly degenerate modes ν19 and ν2 can be differentiated and unambiguously assigned. The observed difference of π between the coherent phases of totally symmetric ag modes (ν11, ν2, ν10) and non totally symmetric b1g modes (ν19) confirms a correlation with normal mode symmetry. Using the CARS lineshape parameters, hypothetical polarized RR spectra for Q band excitation are generated: this enables a direct comparison with experimentally detected polarized RR spectra obtained with preresonant B band excitation. Major changes in spectral parameters such as intensity enhancements and depolarization ratios of prominent macrocycle modes due to the different electronic resonance conditions are discussed. Copyright © 2006 John Wiley & Sons, Ltd.