Symmetry and symmetry breaking in Rydberg-atom intrashell dynamics

Abstract

We have investigated experimentally and theoretically the dynamics of Stark-Zeeman split states in Li(n = 25) Rydberg atoms when they are exposed to a superposition of a slowly varying field and a harmonic RF field. Regular oscillatory structures are observed in the intrashell transitions. By solving the time-dependent Schrödinger equation for the problem it is shown that the dynamics is strongly influenced by the nonhydrogenic core which breaks the dynamical symmetry of the Coulomb problem. It is also shown that the dynamics effectively reduces to that of a two-level atom. The oscillations are remnants of interferences that arise partly due to a phase difference which develops between the two levels when they go through two consecutive one-photon resonances, and partly due to an effective change of the carrier-envelope phase of the coupling field.

Unidentified transitions in one-photon intrashell dynamics in Rydberg atoms

“…This stands in clear contrast with the experimental data which clearly shows that transitions have occurred. As a matter of fact, we find this disagreement very surprising, as in our previous studies on intrashell dynamics in Li, the model was always capable of explaining the experimental results [11,[13][14][15][16].…”

“…The structures disappear at large eccentricities (e > 0.5). Detailed quantum calculations [16,17] suggest that the dynamics is essentially hydrogenic between the resonances even for the largest rf field strengths considered here, and that the much simpler hydrogenic theory of Kazansky and Ostrovsky should apply [22]. Although the experimental results could be consistent with a scenario where population is transferred to higher m states (within the same n shell) that eventually field ionize diabatically, we have found no theoretical evidence for this.…”

“…The effect of the core is modeled within the framework of quantum defect theories (see Ref. [16] for further details about the theoretical model). Varying the value and direction of the stray field, applying pulses of different durations and intensity profiles, varying the strength of the rf field, and finally changing the eccentricity of the initial state, we could not find any explanation for the presence of the new structures in the SFI spectra.…”

“…The formation of CESs in external fields was described in [2,3,8]. Intrashell dynamics of the Stark-Zeeman split n = 25 shell in Li was studied extensively over the last 10 years [9][10][11][12][13][14][15][16][17].…”

“…Quantum calculations taking the lithium core into account within the framework of quantum defect theories [11,16,21] show that the dynamics in between the one-photon resonance is hydrogenic [16], that is, the nonhydrogenic core can be totally neglected, even when the atoms are strongly driven by the rf field. This stands in clear contrast to the situation at frequencies above, below, or at the two resonances where quantum defects are very important except when transitions are weakly driven.…”