Hyperfine-frequency shifts of alkali-metal atoms during long-range collisions

摘要

We have experimentally studied the formation of ultracold RbCs molecules by photoassociation at shortninternuclear range followed by spontaneous emission. The observation of new excited levels with respect tonour previous work [Gabbanini and Dulieu, Phys. Chem. Chem. Phys. 13, 18905 (2011)] on both sides of thenRb(5S1/2) + Cs(6P3/2) dissociation limit gives information on the state responsible for molecule formation.nThe molecules are mainly formed in deeply bound levels of the electronic triplet ground state. The observednphotoassociation transitions present differences in terms of saturation.nCollisions with chemically inert atoms or molecules change the hyperfine coupling AI · S of an alkali-metalnatom through the hyperfine-shift interaction δA I · S. This interaction is responsible for the pressure shifts of thenmicrowave resonances of alkali-metal atoms in buffer gases, is an important spin interaction in alkali-metal–nnoble-gas van der Waals molecules, and is anticipated to enable the magnetoassociation of ultracold moleculesnsuch as RbSr. An improved estimate is presented for the long-range asymptote of this interaction for Na, K,nRb, and Cs. To test the results, the change in hyperfine coupling due to a static electric field is estimated andnreasonable agreement is found.