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Polarization-sensitive resonance coherent anti-Stokes Raman scattering spectroscopy of magnesium octaethylporphine (MgOEP) in dichloromethane is reported. The measurements were performed in resonance with the Q-band electronic absorption where linear resonance Raman spectroscopic measurements were foiled by excessive fluorescence. A high porphyrin concentration allowed direct identification of the different vibrational mode symmetries. Complementary vibrational information was obtained from B -band resonance Raman spectra. MgOEP was found to be structurally similar to nickel octaethylporphine, but with an expanded porphyrin core.

We report on an experimental setup which has been developed to perform efficient nanosecond time-resolved coherent anti-Stokes Raman scattering (CARS) experiments using either the scanning CARS or the broadband CARS technique. A special electronic device has been constructed that allows the CARS probing laser system to be triggered with a variable delay after the excitation pulse of a nitrogen laser and furthermore prevents any temporal drifts of the nitrogen laser emission. The acquisition of the broadband CARS spectra is based on the recently developed scanning multichannel technique, which is applied in the present paper to CARS spectroscopy. Several examples of ground- and excited-state CARS spectra are shown to demonstrate the performance of the setup and to point out the benefits and limitations of the various measurement techniques. Moreover, we present CARS spectroscopic investigations of triplet relaxation processes in order to illustrate the feasibility of the designed spectrometer for nanosecond time-resolved CARS experiments.

The applicability of a recently suggested coherent anti-Stokes Raman spectroscopic (CARS) reflection technique to investigatiom of strongly absorbing materials was tested. The underlying principle is that the CARS signal generated in the surface layers of the sample is detected as a beam which is backscattered from the surface of an opaque medium rather than in transmission. A special experimental arrangement was used which allowed CARS spectra to be obtained with reasonable signal strength. As an example, experimental results for a TS6 (hexa-t,4diynylene di-p-toluenesu1phonate)polydiacetylene single crystal are presented. Spectra obtained at different angles of incidence are discussed.

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