High resolution zero kinetic energy photoelectron spectroscopy of benzene and determination of the ionization potential

We report the direct high‐resolution determination of the ionization potential of benzene and the observation of rotational structure in the vibronic ground state of the benzene ion. We employ a new technique of two‐color high‐resolution zero kinetic energy photoelectron spectroscopy (ZEKE‐PES) via selection of an intermediate resonant (neutral) state. The ZEKE‐PES method allows for the investigation of rotationally resolved photoionization dynamics and the direct high‐precision determination of ionization potentials, the precision being derived directly from the laser wavelength calibration. For benzene we determine an IP of 74 555.0±0.4 cm⁻¹. We compare this method to ionization potential measurements from ion yield measurements under various conditions.