Picosecond Transient Infrared Spectroscopy of 4-Dimethylamino- 4′-Nitrostilbene in the Fingerprint Region

A picosecond infrared spectrometer covering nearly the whole fingerprint region hasbeen constructed. The infrared absorption spectrum of electronically excited 4-dimethylamino-4′-nitrostilbene, which has an intramolecular charge-transfer character,has been recorded. The observed infrared intensities are generally very strong (molarabsorption coefficients as high as 3×10 3 mol -1 dm 3 cm -1 ). The infrared spectral patternof the excited species is similar to that of the Raman spectrum. It is suggested that suchfeatures can be explained in terms of strong vibronic coupling in the observed excitedspecies. Polarization measurements have also been performed.