Nanosecond time-resolved resonance CARS spectroscopy using the scanning multichannel technique

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.