Ionization of very-high-n Rydberg atoms by half-cycle pulses in the short-pulse regime

The ionization of potassium Rydberg atoms with n similar to 388 and n similar to 520 by pulsed electric fields whose durations, which range from similar to 2 to similar to 110 ns, span the transition from the short-pulse to the long-pulse regime is investigated experimentally and the data compared with the results of classical trajectory Monte Carlo calculations. We observe excellent agreement between theory and experiment providing a benchmark test for the validity of the classical limit of ionization. Very-high-n atoms provide an excellent tool with which to probe the response of atoms to pulsed electric fields in the short-pulse regime.