A radiofrequency field induced anisotropy of atomic collisions

Alexander N. Petrov, Eite Tiesinga, Svetlana Kotochigova

We explore the anisotropic nature of Feshbach resonances in the collision between ultracold highly magnetic submerged-shell dysprosium atoms in their energetically lowest magnetic sublevel, which can only occur due to couplings to rotating bound states. This is in contrast to well-studied alkali-metal atom collisions, where broadest (strongest) Feshbach resonances are hyperfine induced and due to rotationless bound states. Our first-principle coupled-channel calculation of the collisions between these spin-polarized bosonic dysprosium atoms reveals a strong interplay between the anisotropies in the dispersion and magnetic dipole-dipole interaction. The former anisotropy is absent in alkali-metal and chromium collisions. We show that both types of anisotropy significantly affect the Feshbach spectrum as a function of an external magnetic field. Effects of the electrostatic quadrupole-quadrupole interaction are small. Over a 20 mT magnetic field range, we predict about 10 Feshbach resonances and show that the resonance locations depend on the dysprosium isotope.

M. N. Hack

Sergey Alyabyshev, Timur V. Tscherbul, Roman V. Krems

We present a rigorous study of low-temperature collisions of polar molecules and atoms in a microwave laser field. Our calculations show that inelastic relaxation of molecules in a microwave cavity may occur through collision-induced absorption of photons stimulated by the anisotropy of the atom-molecule interaction potential. Our results indicate that molecular collisions at temperatures below 1 K can be efficiently manipulated with microwave laser fields of moderate strength.

В. В. Зверев, V. G. Pokazan'ev

Vsevolod V. Balashov, Alexei N. Grum-Grzhimailo, Nikolai M. Kabachnik

Raghavan K. Easwaran

In this thesis, I describe the spectroscopic investigations and preliminary results of evaporative cooling of rubidium atoms done on a magnetic trap dressed with a radiofrequency field. Unlike the case of a static magnetic trap, where a single radiofrequency photon is used to outcouple atoms we have demonstrated that a multiphoton transition is necessary. This transitions are nearly resonant with the energy spacing of the radiofrequency dressed states. The evaporation efficiency is not the same for all the observed transitions: the transition involving a two photon process is more efficient compared to the others. Preliminary results of evaporative cooling in a radiofrequency dressed trap are discussed. The quantum degeneracy is not reached as it is difficult to reach thermalization due to the strong anisotropy in the trap. A way to render the evaporative cooling more efficient is to increase the horizontal oscillation frequencies. Finally, we discuss a method to load the atoms into a radiofrequency dressed quadrupole trap, leading to large oscillation frequencies in the horizontal directions.