Hyperfine Interaction In Atoms Research Articles

Competing interactions in strongly driven multi-level systems

We experimentally study the level mixing, splitting and repulsion of an optically driven atomic multi-level system under two competing interactions. The strength of the optical coupling is increased until it surpasses the atomic hyperfine interaction responsible for mixing the magnetic substates. Due to the multi-level character of the coupled state space, the level shifts exhibit complex behavior reminiscent of the Paschen–Back effect. Our results show that multi-level effects can have significant influence for strong external drive, differing from a simple model of effective non-interacting two-level systems. These results highlight the relevance of imperfections of the light polarization or initial state preparation in strongly optically driven systems.

Model for the hyperfine structure of electronically excited KCs molecules

A model for determining the hyperfine structure of the excited electronic states of diatomic bialkali heteronuclear molecules is formulated from the atomic hyperfine interactions, and is applied to the case of bosonic $^{39}$KCs and fermionic $^{40}$KCs molecules. The hyperfine structure of the potential energy curves of the states correlated to the K($4s\,^2S_{1/2}$)+Cs($6p\,^2P_{1/2,3/2}$) dissociation limits is described in terms of different coupling schemes depending on the internuclear distance $R$. These results provide the first step in the calculation of the hyperfine structure of rovibrational levels of these excited molecular states in the perspective of the identification of efficient paths for creating ultracold ground-state KCs molecules.

Magnetic control of ultra-cold 6Li and 174Yb(3P2) atom mixtures with Feshbach resonances

We theoretically evaluate the feasibility to form magnetically-tunable Feshbach molecules in collisions between fermionic 6Li atoms and bosonic metastable 174Yb(3P2) atoms. In contrast to the well-studied alkali-metal atom collisions, collisions with meta-stable atoms are highly anisotropic. Our first-principle coupled-channel calculation of these collisions reveals the existence of broad Feshbach resonances due to the combined effect of anisotropic-molecular and atomic–hyperfine interactions. In order to fit our predictions to the specific positions of experimentally-observed broad resonance structures (Dowd et al 2014) we optimized the shape of the short-range potentials by direct least-square fitting. This allowed us to identify the dominant resonance by its leading angular momentum quantum numbers and describe the role of collisional anisotropy in the creation and broadening of this and other resonances.

State-dependent potentials in a nanofiber-based two-color trap for cold atoms

We analyze the ac Stark shift of a cesium atom interacting with far-off-resonance guided light fields in the nanofiber-based two-color optical dipole trap realized by Vetsch \textit{et al.} [Phys. Rev. Lett. \textbf{104}, 203603, (2010)]. Particular emphasis is given to the fictitious magnetic field produced by the vector polarizability of the atom in conjunction with the ellipticity of the polarization of the trapping fields. Taking into account the ac Stark shift, the atomic hyperfine interaction, and a magnetic interaction, we solve the stationary Schr\"odinger equation at a fixed point in space and find Zeeman-state-dependent trapping potentials. In analogy to the dynamics in magnetic traps, a local degeneracy of these state-dependent trapping potentials can cause spin flips and should thus be avoided. We show that this is possible using an external magnetic field. Depending on the direction of this external magnetic field, the resulting trapping configuration can still exhibit state-dependent displacement of the potential minima. In this case, we find nonzero Franck-Condon factors between motional states of the potentials for different hyperfine-structure levels and propose the possibility of microwave cooling in a nanofiber-based two-color trap.

Molecular hyperfine parameters in the 1 3Σ u + and 1 3Σ g + states of Li2, Na2, K2 and Rb2

Magnetic hyperfine parameters have been computed for the 1 3 Σ + and 1 3 Σ + states of Li2 ,Na2 ,K2 and Rb2. The parameters were computed with MCSCF wavefunctions and the calculations were repeated for a series of internuclear distances. The results are compared with a recent observation of the hyperfine structure in Rb2, and to the atomic hyperfine parameters. The available empirical data are reproduced with high accuracy. For the present systems, the molecular hyperfine parameters are largely determined by the corresponding atomic hyperfine interactions. The computed molecular parameters at the dissociation limit deviate at most 11% from the experimentally determined atomic ones.

Abundance ratios of mercury isotopes by 6 s 6 p 3 P 1 -intermediate state excitation with resonance ionization mass spectrometry

The isotope-selective excitation of mercury via the 6s6p3P1 intermediate state excitation is studied with two-color resonance ionization mass spectrometry to determine abundance ratios of stable mercury isotopes. Lifetime, isotopic shifts, and hyperfine structure (HFS) splittings are measured. Atomic hyperfine interaction constants are determined. Line strengths of the ten components of the 6s21S0→ 6s6p3P1 transition are used for isotope ratio determinations. Ion signal intensities of even-mass components directly give the isotopic abundance, in contrast to the odd-mass components, for which the sum of the HFS components results in an anomalously high response for the isotopic abundance. The laser bandwidth dependence of the excitation and population probabilities of magnetic HFS sublevels due to linear polarization of the radiation are discussed. These considerations yield reasonable values for the apparent odd-mass isotope abundance.

Polarization change of light scattering near a2 P 3/2?2 S 1/2 resonance

We have investigated experimentally and theoretically the change in the polarization state of polarized laser light scattered near a2P3/2↔2S1/2 atomic resonance as function of the laser frequency. For a collision free Na vapor at number densities <1010cm−3 it is found experimentally, that the polarization degree changes from a small level at frequencies between hyperfine components of the 32P3/2↔32S1/2 transition towards high values at separations large compared to the hyperfine splitting. By comparison with scattering theory it is shown, that this change is typical for the transition from resonant to nonresonant scattering in the presence of atomic hyperfine interaction.

Electron-Nucleus Hyperfine Interaction in Atoms

It is pointed out that the so-called “hyperfine interaction” between the magnetic moment of a nucleus and the spins of the surrounding electrons is completely classical in origin. Quantum mechanics is irrelevant and not necessary to the understanding of this coupling. A simple derivation, based only on classical static magnetism, is given of Fermi's formula for the interaction energy.