Microwave Ionization of Hydrogen Atoms: Experiment versus Classical Dynamics

Abstract

Ionization of hydrogen atoms with principal quantum number n =32, 40, and 51-74^by a 9.92-GHz electric field F(/) = z/ocoscof was studied with a superimposed static electric field F s = 0, 2, 5, and 8 V/cm. The measured field strengths Fo(\0°/o) at which 10% of the atoms were ionized are in excellent agreement with classical calculations in both one and two spatial dimensions. Covering finer detail as well as gross structure of the n dependence of FoOOo/o), the agreement supports the application of classical dynamics to the analysis of this strongly perturbed quantum system.

Non-dispersive wave packets in periodically driven quantum systems

“…Hence, state of the art experiments are "blind" for the details of the atomic excitation process on the way to ionization, and therefore not suitable for the unambiguous identification of individual eigenstates of the atom in the field, notably of non-dispersive wave-packets. The case is getting worse with additional complications which are unavoidable in a real experiment, such as the unprecise definition of the initial state the atoms are prepared in [133,137,[209][210][211][212][213][214][215][216], the experimental uncertainty on the envelope of the amplitude of the driving field experienced by the atoms as they enter the interaction region with the microwave (typically a microwave cavity or wave guide) [200,211,217], stray electric fields due to contact potentials in the interaction region, and finally uncontrolled noise sources which may affect the coherence effects involved in the quantum mechanical transport process [218]. On the other hand, independent experiments on the microwave ionization of Rydberg states of atomic hydrogen [132,137], as well as on hydrogenic initial states of lithium [217], did indeed provide hard evidence for the relative stability of the atom against ionization when driven by a resonant field of scaled frequency ω 0 ≃ 1.0.…”

Population Trapping in Extremely Highly Excited States in Microwave Ionization

“…Several immediately relevant examples occur in the microwave ionization of Rydberg atoms. Classical stabilization of Rydberg atoms against microwave ionization occurs when the microwave frequency or one of its harmonics matches the classical Kepler frequency of the Rydberg atom [2][3][4]. Of particular interest for this work, it was observed long ago in classical calculations that the Rydberg atom could be left in very high lying states by a microwave pulse [5][6][7].…”

Quantum interference in the field ionization of Rydberg atoms

“…Multiphoton ionization with microwave fields has provided insight into the connection between a field and photon picture of the electron's pathway to freedom [7]. In the case where the microwave frequency is close to that of the classical Kepler frequency a variety of interesting behaviors have been observed including resonances in the ionization spectrum [8,9], population of extremely highly excited states [10,11], and a phase-dependent threshold for ionization of a wave packet [12,13]. On the microsecond time scale, the widely used technique of state selective field ionization relies on the relative ease with which the electron can be liberated with a simple and reproducible electric field pulse [14].…”