Autoionizing Rydberg and zero electron kinetic energy states in Ar

We present spectroscopic data for the autoionizing np Rydberg manifold of Ar atoms together with the lifetimes of its Zeke states (Rydbergs of very high n’s studied by time resolved ZEKE spectroscopy). The lower n Rydberg states have finite widths, indicating a fast autoionization process that diminishes with increasing n (as n3). This trend cannot be used to predict the behavior of the high Zeke states whose lifetimes are almost 2 orders of magnitude longer than the lifetimes extrapolated from the low n values.