IONIZATION OF RYDBERG ATOMS BY HALF-CYCLE PULSES - EFFECT OF PULSE-SHAPE AND RISE-TIME

The ionization of potassium np Rydberg atoms with n similar to 388 by pulsed unidirectional electric fields, termed half-cycle pulses (HCPs) , with various well characterized shapes (rectangular, triangular and sawtooth) and durations T-p comparable to the classical electron orbit al period T-n is investigated. The experimental results are compared w ith classical trajectory Monte Carlo (CTMC) simulations and the classi cally scaled results of quantum calculations undertaken at n = 5. The data show chat in the intermediate regime, T-p greater than or similar to T-n, the threshold field for ionization becomes sensitive to the s hape and rise time of the HCP, increasing with increasing rise time. F or each pulse shape, the agreement between the experimental measuremen ts and both the CTMC and quantum calculations is very good.