Microwave “ionization” of excited hydrogen atoms: How nonclassical local stability brought about by scarred separatrix states is affected by broadband noise and by varying the pulse envelope

Abstract

Abstract Studies of the microwave “ionization” of excited hydrogen atoms have shonn (so far) six regimes of dynamical behavior as one changes the scaled frequency, which is the ratio of the driving frequency ω and the classical Kepler frequency ω k . After a brief description of each regime, we focus on the results of recent experiments probing the detailed semiclassical behavior in two of them. Observed nonclassical local stability that, nevertheless, classically scales has been explained theoretically as being brought about by scarred quantal wavefunctions anchored semiclassically to the (broken) separatrix regions in the classical phase space above and below the main nonlinear resonance zone centered near ω ω k = 1 1 . The experimental data show that the upper and lower separatrix states states are affected differently by broadband noise added to the coherent microwave field and by variations in the microwave pulse envelope. Implications of these results for future work are discussed.