NORMAL-MODES OF 4-AMINOBENZONITRILE (4-ABN) - A COMPARISON OF PM3 CALCULATIONS WITH EXPERIMENTAL JET-COOLED SPECTROSCOPY

The geometry and the normal modes of 4-aminobenzonitrile (4-ABN) in th e ground and first excited states have been computed using PM3 formula tion. These calculated results, together with previous vapour phase ab sorption and infrared studies, are used to examine the vibrational mod es in the laser-induced fluorescence (LIF) excitation and emission spe ctra of jet-cooled 4-ABN. The calculated vibrational frequencies of th e normal modes show good agreement with experiment both for the electr onic ground and the first excited states, but there is a relatively la rge discrepancy in the position of the electronic origin transition.