Rotationally resolved electronic spectroscopy of 4-aminobenzonitrile

The rotationally resolved fluorescence excitation spectrum of the 0(0)(0) band in the S-1 <-- S-0 transition of 4-aminobenzonitrile (ABN) was recorded, at 299 nm, by using laser induced fluorescence in a molecular beam apparatus. This spectrum exhibits pure b-type character, which indicates that the electronic transition moment vector is oriented along the short molecular axis. The rotational constants of the S-0 and S-1 states were determined. In addition, the rotationally resolved fluorescence excitation spectra of two vibronic bands in the S-1 state, at 807 and 816 cm(-1), were recorded. The molecular structure of the ABN molecule is discussed by comparing the rotational constants and the inertial defects. (C) 1997 Elsevier Science B.V.