Coherent anti-Stokes Raman scattering with broadband excitation and narrowband probe.

An improved CARS setup based on noncollinear optical parametric amplifiers (NOPAs) is presented which combines broad tunability and a wide excitation bandwidth with good spectral and temporal resolution. Picosecond Raman pump and probe pulses are generated by a modified narrowband NOPA. Combining them with sub-50 fs Stokes pulses results in highly time resolved CARS spectra with line widths down to 20 cm-1. The determination of a vibrational decoherence time is demonstrated for chloroform. Beating phenomena in case of overlapping Raman bands and an increase of spectral structure for coalescing bands are observed for cyclohexane and an ionic liquid respectively.