Influence of the hyperfine structure of the atomic states on the collective effects in the Rb 2 quasi-molecule
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Influence of the Hyperfine Structure of the Atomic States on the Collective Effects in the Rb2 Quasi-molecule I. M. Sokolov St. Petersburg State Polytechnic University, St. Petersburg, 195251 Russia Institute of Analytic Instrument Making, Russian Academy of Sciences, St. Petersburg, 198095 Russia e-mail: [email protected] Received March 6, 2017
Abstract—A consistent quantum approach is used to study the influence of intraatomic spin–orbit and hyperfine interactions on the character of a resonance dipole–dipole interatomic interaction and, hence, collective effects. For this purpose, the collective spontaneous decay of excited states and the spectral dependence of the total scattering cross section of a monochromatic light wave are analyzed in the system consisting of two rubidium-87 atoms. The modification of the radiation properties and the interaction of the atoms with external radiation are studied as functions of the interatomic distance. The presence of a complex structure of the sublevels of both the ground and excited states is shown to modify the collective effects substantially as compared to the case when this structure is absent. DOI: 10.1134/S1063776117090175
1. INTRODUCTION Current deep interest in studying cold and ultracold atomic ensembles is caused by both a number of their unique physical properties and a wide spectrum of their possible practical application in the problems of quantum metrology, frequency standardization, and quantum-information applications [1– 4]. Most methods of diagnostics of these ensembles and the majority of proposed schemes their application are based on their interaction with electromagnetic radiation. The optical properties of the atomic clouds cooled in special-purpose traps to a temperature of several microkelvins have some specific features. The main specific feature consists in the fact that, because of a low average velocity, atoms are characterized by a very large cross section of resonance interaction with light. Therefore, it is necessary to take into account the collective polyatomic effects caused by multiple light scattering inside an ensemble for a relatively rarefied cloud. The collective effects concern the fundamental problems of quantum electrodynamics, such as the change in the rate of spontaneous atomic decay in an external medium and the related phenomena of superand subradiance, the cooperative Lamb shift, laser generation in a random medium, and weak and strong (Anderson) light localization. The role of collective effects becomes more important with the atomic concentration. In recent years, dense cold clouds, the interatomic distances in which are comparable with the optical wavelength, are
of particular interest due to the possibility of formation of ensembles with a very large optical thickness (one hundred or more), which is very important to increase the efficiency of their practical application. The collective effects in such dense media are substantially caused by the influence of a resonance interatomic dipole–dipole i
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