Influence of polarization effects on the exchange interaction of atoms

Victor V. Goldman, Isaac F. Silvera

Alfred Owusu, R. W. Dougherty, G. Gowri +2 more

To enhance the current understanding of mechanisms contributing to magnetic hyperfine interactions in excited states of atomic systems, in particular, alkali-metal atom systems, the hyperfine fields in the excited $5{}^{2}{S}_{1/2}--8{}^{2}{S}_{1/2}$ states of potassium and $8{}^{2}{S}_{1/2}--12{}^{2}{S}_{1/2}$ states of francium atoms have been studied using the relativistic linked-cluster many-body perturbation procedure. The net theoretical values of the hyperfine fields for the excited states studied are in excellent agreement with available experimental data for both atoms. There is a significant decrease in importance of the correlation contribution in going from the ground state to the excited states, the correlation contributions as ratios of the direct contribution decreasing rapidly as one moves to the higher excited states. However, the contribution from the exchange core polarization (ECP) effect is nearly a constant fraction of the direct effect for all the excited states considered. Physical explanations are offered for the observed trends in the contributions from the different mechanisms. A comparison is made of the different contributing effects to the hyperfine fields in potassium and francium to those in the related system, rubidium, studied earlier. Extrapolating from our results to the highly excited states of alkali-metal atoms, referred to as the Rydberg states, it is concluded that in addition to the direct contribution from the excited valence electron to the hyperfine fields, a significant contribution is expected from the ECP effect arising from the influence of exchange interactions between electrons in the valence and core states.

Valery Alexandrovich Astapenko, L. A. Bureeva, Valerii S. Lisitsa

Liu Bowen, Xiangyang Zhou, Yuhao Liu +2 more

Abstract The spin polarization and spatial homogeneity of alkali metal atoms are critical characteristics that determine the performance of spin-exchange relaxation-free magnetometers. In buffer gas cells, these characteristics are influenced by optical broadening and alkali atomic motional restriction imposed by the buffer gas. In coated cells, the protective effect of the coating on atomic spins, combined with rapid atomic diffusion, leads to significantly superior spin polarization characteristics compared to those in high-pressure buffer gas cells. However, due to neglecting the influence of atom-coating interactions on atomic motion, the existing spin polarization and spatial distribution models fail to accurately describe the polarization characteristics in coated cells. In this paper, based on the Langevin–Bloch equation, a dynamic model considering interaction effects between alkali metal atoms and the coating as well as between the pump light and the hyperfine levels of alkali metal atoms is proposed to accurately describe the spin polarization and spatial distribution in coated cells. To validate the proposed model, a series of experiments were carried out. The results demonstrate that coated cells can maintain high spin polarization and spatial homogeneity even under conditions of low pump intensity and high temperature, which are in good agreement with the simulations. This work provides a theoretical reference for the design of high-performance and low-power quantum sensors.

Mahito Kohmoto, U. Fano

H Muller, Joachim Keßler

The change in the polarization vector perpendicular to the scattering plane is examined for collisional excitation of mercury atoms by electrons at a collision energy of 40 eV. The three measured polarization parameters for excitation of the states 6 1P1 and 6 3P1 give information about the influence of spin-orbit and exchange interaction on the excitation process. The results, which are quite different for the two excited states, are compared with the latest theoretical data.