Optical detection of nonradiating alkali atoms in solid helium

Area of Science:

• Atomic Physics
• Quantum Optics
• Condensed Matter Physics

Background:

• Rubidium (Rb) and Cesium (Cs) are alkali metals with distinct atomic properties.
• Helium-4 (He) crystals provide a unique matrix for studying atom-solid interactions.
• Optical detection methods are crucial for probing atomic states in condensed matter.

Purpose of the Study:

• To optically detect nonfluorescing rubidium isotopes within a body-centered cubic helium-4 crystal.
• To investigate the influence of the helium matrix on the magnetic resonance spectra and optical pumping of Rb and Cs.
• To determine the effective g(F) factors of Rb isotopes in the He matrix.

Main Methods:

• Optical detection of nonfluorescing 85Rb and 87Rb atoms.
• Double resonance technique to detect weak resonance absorption.
• Comparative study of (optically detected) magnetic resonance spectra of 85Rb, 87Rb, and 133Cs.

Main Results:

• Nonfluorescing 85Rb and 87Rb atoms were successfully detected in a 4He crystal.
• Resonance fluorescence of Rb was found to be strongly quenched by the He matrix.
• Effective g(F) factors of Rb isotopes were inferred and found to be unperturbed by the He matrix (at 2 x 10(-4)).
• Optical pumping mechanisms differ: Rb via depopulation, Cs via repopulation.

Conclusions:

• The helium-4 matrix does not significantly perturb the effective g(F) factors of implanted rubidium isotopes.
• Optical pumping pathways for rubidium and cesium in helium differ.
• This study demonstrates the feasibility of optically probing alkali atoms in solid helium.