LIFETIMES OF RYDBERG STATES IN ZERO-ELECTRON-KINETIC-ENERGY EXPERIMENTS .1. ELECTRIC-FIELD-INDUCED AND COLLISIONAL ENHANCEMENT OF NO PREDISSOCIATION LIFETIMES

Lifetime measurements are reported for high principal quantum number (n=40-125) Rydberg states of the NO molecule, prepared using state-selective double resonance excitation with a narrow bandwidth laser. The influence of (i) the application of a dc electric field, and (ii) interactions of the Rydberg states with surrounding ions, were investigated. It is demonstrated that the presence of dc electric fields can lead to enhancements in the lifetimes due to l-mixing, and the conclusion is reached that under the conditions existing in a typical zero-electron-kinetic-energy (ZEKE) photoelectron spectroscopy experiment, the Rydberg states involved are excited in a regime where l-mixing is expected to be significant. It is observed that l- and m -mixing collisional interactions provide a further mechanism to stabilize the optically prepared Rydberg states, beyond the limits which can be achieved by l-mixing alone. © 1995 American Institute of Physics.