Observation of Electric-Field-Induced Resonances above the Ionization Limit in a One-Electron Atom

Abstract

Measurements of the relative photoionization cross sections of Rb in the presence of various strengths of external electric fields are reported. Systematic, field-dependent, resonance structure is observed not only for energies above the classical field-ionization limit, but above the zero-field ionization limit as well. A striking dependence of the cross section upon light polarization is also observed.We report the results of an investigation of the wavelength dependence of the single-photon photoionization cross section of ground-state Rb in the presence of externally applied electric fields, For each field value, a systematic resonance structure versus wavelength was observed, not only for energies above the classical field-ionization threshold (which has been previously reported), but above the zero-field ionization limit as well. The observation of electric-field-dependent resonances in the photoionization cross section above the zero-field limit in a one-electron-like atom is surprising and to our knowledge has not been previously reported, In this Letter we present some relevant results of our experiment, discuss the physical mechanism responsible, develop a model whose predictions are in good agreement with our data, and attempt to place the results in proper perspective relative to recent measurements of field ionization and Stark effects in alkali atoms 0 For detailed study of the cross section, we employed a collison-free, low-density (%> 10 9 /cm 3 ) atomic beanu The Rb atomic beam was irradi-1463

Interaction of laser radiation with a negative ion in the presence of a strong static electric field

“…The experimental observations of the oscillatory resonance behaviour in the photoionization spectra of Rb both above the classical ionization threshold [26] and especially above the zero-field-ionization threshold [27] stimulated detailed theoretical investigations of atomic photoionization [28][29][30][31][32][33][34][35] as well as photodetachment [31,34,36] in the presence of a weak static electric field. Subsequent experimental observations [37] of electric-fieldinduced resonances in the photodetachment spectrum of H − induced a resurgence of activity on primarily single-photon detachment processes in the presence of a weak external electric field [38][39][40][41][42][43][44][45][46].…”

Electric-field effects on the closed orbits of the diamagnetic Kepler problem

“…In the extreme case of a pure electric field, there exists an exact quantum solution due to the separability of the Schrödinger equation. Therefore, the classical motion in this system is regular everywhere [11][12][13]. By applying both fields at varying comparable strengths we are able to observe the system evolving from regular to chaotic dynamics [6,8].…”

Rydberg-electron wave-packet dynamics in parallel electric and magnetic fields and evidence for stabilization

“…2. From the complexity of both the calculated Stark map and of previous &equency-resolved spectroscopic studies of the resonances above E, [15,16], it might seem surprising that such a variety of energy level spacings and intensities give rise to time-resolved spectra which show such simple periodic motion. Note tribution to the wave-packet dynamics.…”