On the role of ions in pulsed field ionization zero–kinetic–energy photoelectron spectroscopy

Abstract

The high Rydberg states probed by pulsed field ionization (PFI) zero–kinetic–energy (ZEKE) photoelectron spectroscopy are usually produced simultaneously with ions. These ions can have a profound influence on the appearance of a ZEKE photoelectron spectrum. It is now widely accepted that ions can lead to a considerable stabilization of high Rydberg states with respect to internal decay processes such as predissociation and autoionization. Two further effects of ions on the outcome of a ZEKE photoelectron spectroscopic experiment are demonstrated: (1) high ionic concentrations can modify the response of atomic and molecular Rydberg state populations to pulsed electric fields; (2) high ionic concentrations can have a detrimental effect on the resolution of a ZEKE photoelectron spectrum. These effects are illustrated by experimental results, which include the determination of the structure of a neutral molecule, the ammonium radical, by PFI–ZEKE spectroscopy.