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Journal of Physics Conference Series

Suppression of multiphoton intrashell resonances in Li Rydberg atoms

A Waheed, Daniel E. Fregenal, Ø Prette, Morten Førre, B.T. Hjertaker, Erik Horsdal, Ingjald Pilskog, Jana Preclíková

Published Nov 5, 2012• 0 citations
Publisher

Abstract

Multiphoton intrashell resonances are observed and measured quantitatively for coherent elliptic states, prepared in orthogonal DC electric and magnetic fields and perturbed by a linearly polarized RF-field. Strong suppressions of the resonances are found at certain values of the eccentricity e of the initial states.
DOI
10.1088/1742-6596/388/2/022052

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One-photon intrashell transitions in strongly driven Li (n=25n=25n=25) atoms are studied experimentally. The degeneracy of the nnn shell is lifted by orthogonal dc electric and magnetic fields, which also define the eccentricity of the initial coherent elliptic state. The transitions are driven by a radio frequency pulse linearly polarized parallel to the major axis of the ellipse. A small dc electric field component parallel to the magnetic field splits the one-photon resonance into two, and transitions in between are studied by state-selective field ionization. Unexpected lines in the ionization spectra relating to unknown transitions are found and discussed.
We measure for the first time, to our knowledge, NNN-photon intrashell resonances, widths, and Bloch-Siegert shifts up to N=23N=23N=23. Rydberg atoms of Li (n=25)(n=25)(n=25) in a rotating electric field and a static, in-plane electric or magnetic field are used. The measurements, in conjunction with theoretical estimates, precisely determine the characteristics of the resonances (shifts and widths) and their dependence on the strength of the rotating field.
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The evolution of Rydberg states of Li in time-dependent fields was studied with special emphasis on the influence of the Li(1s2)+ core. The strengths and rates-of-change of the fields were such that the dynamics involves states of only a single shell (intrashell dynamics). For sufficiently slow variations, the Rydberg states are transformed adiabatically but for faster variations, intrashell transitions do occur. We present experimental approximate probabilities for adiabatic transformation of the Rydberg states and compare with theoretical predictions with and without core effects included. The core can perturb the dynamics significantly. Circumstances under which this is likely to be the case are discussed.