Mass analyzed threshold ionization spectroscopy of 4-aminobenzonitrile cation

Mass analyzed threshold ionization (MATI) and two-color resonant two-photon ionization (R2PI) methods were used to investigate the ionic properties of 4-aminobenzonitrile (4-ABN). The adiabatic ionization energy of this molec ule was determined to be 66493 +/- 3 cm(-1) by the MATI spectroscopy and 66 494 +/- 7 cm(-1) by the two-color R2PI spectroscopy. The active vibrations of the 4-ABN cation include the in-plane ring deformation, CC stretching, C -CN stretching, and CH bending motions. The present experimental results ar e well supported by our ab initio and density functional theory calculation s. (C) 2000 Elsevier Science B.V. All rights reserved.