ROVIBRATIONAL STRUCTURE OF NO2+ AND STATE-TO-STATE DYNAMICS IN THE HIGH-RESOLUTION THRESHOLD PHOTOIONIZATION OF NO2

Triple-resonant zero-kinetic-energy (ZEKE) photoelectron spectroscopy is employed to characterize the rovibrational structure of NO2+. Relative threshold positions determine vibrational frequencies and rotational constants; while anomalous, and in some cases forbidden, intensities of transitions provide information on rotational and vibrational coupling between the NO2+ core and electronic degrees of freedom associated with Rydberg orbitals of very high principal quantum number. Trends in the strengths of anomalous threshold photoionization features establish that mode selectivity, which has a pronounced effect on the vibrational autoionization dynamics of NO2, also operates to determine the envelope of rotational-line intensities in threshold photoionization. Competition between rotationally and vibrationally mediated coupling leads to a dependence of the rotational profile on the mode of vibrational motion of the core.