Excited-state Raman spectroscopy with and without actinic excitation: S1 Raman spectra of trans-azobenzene

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S-1 and S-0 spectra of trans-azobenzene in n-hexane. The S-1 spectra were also measured conventionally, upon n pi* (S-0 -> S-1) actinic excitation. The results are discussed and compared to earlier reports. (C) 2014 AIP Publishing LLC.