Laser induced, dispersed fluorescence spectroscopy, and ab initio calculations of p-cyanophenol

The electronic origin of p-cyanophenol has been assigned to the strongest t ransition in the jet cooled vibronic spectrum at 35547.5 cm(-1). Vibrations of the electronic ground state have been measured by means of dispersed fl uorescence and those of the first electronically excited state by laser ind uced fluorescence. An assignment of the S-0 state vibrations is presented b ased upon ab initio calculations at the MP2 and DFT level of theory. Additi onal CASSCF calculations are presented for both electronic states. The vibr onic activity of several low frequency modes points towards a substantial c hange in geometry of the cyano group upon excitation.