Effect of impulsive transient electric fields on autoionization

Picosecond half cycle pulses (HCPs) have been used to examine the effect of transient electric fields on the autoionization of doubly excited states of calcium. The autoionization yield, following picosecond isolated core excitation (ICE) of $4pnd$ Rydberg states, has been measured as a function of the relative delay between the transient field and the ICE laser pulse. Using single and multiple HCPs in combination with a static electric field, we explicitly investigate the relative importance of static field induced $\mathcal{l}$ mixing, and transient field excitation of high-$\mathcal{l},$ low-$m$ or high-$\mathcal{l},$ high-$m$ states on the suppression of autoionization. Our experimental results can be understood using semiclassical analyses and are well reproduced by quantum simulations.