ZEro Kinetic Energy (ZEKE) spectroscopy relies on electrons produced through delayed
field ionization of the narrow band of high-n Rydberg states which exist just below the
ionization limit of each ionic eigenstate. Using the unique properties of these weakly
bound, stable, high-n Rydberg states (ZEKE states) below the ionization limit rather
than the unbound states above the limit, as in PES, leads to an improvement in
resolution of more than two orders of magnitude. Several different types of ZEKE
experiments, each designed to probe the formation and stability of these states, are
presented here. These experiments were performed with pulsed and static electric fields of
different magnitude and duration at different ion concentrations. The results indicate an
enhanced ZEKE state decay with increasing electric field strengths and an enhanced
formation and stabilization with increasing ion concentrations. A strong interplay
between field strength and ion concentration ZEKE state formation is demonstrated.
The strong influence of electric fields and ion concentrations on the physical properties
of the ZEKE state, above and below the classical ionization threshold, is also
demonstrated through late time (tens of microseconds) decay rate measurements.
The Role of Electric Fields and Ion Concentrations in the Formation and Stabilization of High-n
Rydberg States
