Mode-dependent vibrational autoionization of NO2

Triple-resonance excitation and high-resolution photoelectron spectroscopy were combined to study the mode dependence of vibrational autoionization in Rydberg states of NO2. Photoselection isolates vibrational autoionization via the symmetric stretching vibration, nu(1), and the bending vibration, nu(2). The previously characterized Fermi resonance between one quantum of nu(1) and two quanta of nu(2) [H. Matsui , J. Mol. Spectrosc. 175, 203 (1996)] allows the comparison of the vibrational autoionization matrix elements for these two modes. The squared matrix element for vibrational autoionization via the symmetric stretch is found to be approximately 35 times greater than that for the bend, which is also consistent with previous results. The results are discussed in terms of existing theoretical models for the autoionization process. (C) 2003 American Institute of Physics.