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The kinetic energy of atoms and molecules at subKelvin temperatures is smaller than perturbations due to interactions with external electric or magnetic fields available in the laboratory. External fields may therefore be used to induce dissociation of weakly bound molecules [1], stimulate forbidden electronic transitions and control dynamics of cold atoms and molecules in a variety of ways [2]. I will review our recent work on mechanisms of manipulating and controlling dynamics of cold atoms and molecules with external electromagnetic fields. In particular, I will discuss the possibility of using electric fields to induce novel three-channel Feshbach resonances [3] and to manipulate spin degrees of freedom of cold molecules.
The mechanism of electric-field-induced resonances is based on the interaction of the instantaneous dipole moment of the collision pair with external electric fields. It will be demonstrated that this interaction is dramatically enhanced in the presence of p-wave shape or magnetic Feshbach scattering resonances near the collision threshold. I will discuss the differential scattering of ultracold atoms and show that moderate electric fields (~100 kV/cm) can be used to manipulate the angular dependence of the scattering cross sections at ultracold temperatures. Finally, I will show that electric fields may also be used to induce or suppress collisional spin decoherence in diatomic molecules. The mechanism of electric-field control of spin-flipping is based on the interplay of the molecule - field interaction and intramolecular spin-rotation couplings. References: 1. R. V. Krems, "Breaking van der Waals molecules with magnetic fields", Phys. Rev. Lett. 93, 013201 (2004). 2. R. V. Krems, "Molecules near absolute zero and external field control of atomic and molecular dynamics", Int. Rev. Phys. Chem. 24, 99 (2005). 3. R. V. Krems, "Controlling collisions of ultracold atoms with dc electric fields", Phys. Rev. Lett. 96, 123202 (2006). |
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