ELECTRIC-FIELD IONIZATION OF HIGH RYDBERG STATES OF AR WITH SEQUENCESOF IDENTICAL PULSES

Novel field-ionization behavior of very high Rydberg states of Ar (n = 50-250) is observed using sequential pulsed electric fields. Fast aut oionization acts as a filter against adiabatic field ionization near t he P-2(1/2) threshold, whereas both diabatic and adiabatic field ioniz ation occur near the P-2(3/2) threshold. Sequences of up to 9 equivale nt pulses yield recurrent field ionization signals near the P-2(3/2) t hreshold, provided that the field returns close to zero between pulses , demonstrating a statistical redistribution of the Rydberg population amongst all states of a given Stark manifold near zero field.