Picosecond transient infrared spectroscopy of electronically excited 4-dimethylamino-4′-nitrostilbene in the fingerprint region (1640-940 cm−1)

A picosecond infrared spectrometer covering nearly the whole fingerprint region has been constructed. The infrared absorption spectrum of electronically excited (S1 state) 4-dimethylamino-4′-nitrostilbene, which is considered to have an intramolecular charge-transfer character, has been recorded. The molar absorption coefficients of observed prominent absorption bands have been estimated to be of the order of 103 mol−1 dm3 cm−1. Measurements of polarization dependence (pump polarization parallel/perpendicular to the probe polarization) have been performed for a few prominent bands. Assignments and polarization characteristics of the observed bands are discussed.