Alkali atoms and molecules on cold helium clusters: spin relaxation due to collisional interactions

Basim R. Bulos

Gerald Auböck, Johann Nagl, Olivier Allard +2 more

Timur V. Tscherbul, Jacek A. Kłos, Piotr Zukowski

A. Hatakeyama, Katsunari Enomoto, T. Yabuzaki

Properties of alkali atoms (mainly rubidium and cesium) in a cold helium gas have been extensively studied. Experiments are performed at temperatures down to 1.2 K using alkali-metal vapor cells containing a helium buffer gas, with alkali atoms driven from the cell walls by one of three loading methods: laser ablation, light-induced atom desorption, and spark discharge. For alkali atoms loaded into the cold helium gas, we have found that the relaxation time of the electronic spin of optically polarized rubidium atoms in the ground state is about a minute, much longer than that achieved in conventional vapor cells at room temperature and above. We have also spectroscopically investigated the interactions of excited alkali atoms with helium atoms, especially the formation of alkali–He exciplexes.

Timur V. Tscherbul, Roman V. Krems

We use rigorous quantum mechanical theory to study collisions of magnetically oriented cold molecules in the presence of superimposed electric and magnetic fields. It is shown that electric fields suppress the spin-rotation interaction in rotationally excited 2Sigma molecules and inhibit rotationally elastic and inelastic transitions accompanied by electron spin reorientation. We demonstrate that electric fields enhance collisional spin relaxation in 3Sigma molecules and discuss the mechanisms for electric field control of spin-changing transitions in collisions of rotationally excited CaD(2Sigma) and ND(3Sigma) molecules with helium atoms. The propensities for spin depolarization in the rotationally excited molecules are analyzed based on the calculations of collision rate constants at T=0.5 K.

M.‐W. Ruf, Andrew J. Yencha, Hartmut Hotop