Dynamics of cold and ultracold molecules in external electromagnetic fields

Roman Krems
UBC Chemistry

The development of experimental techniques for the production of ultracold (nano-Kelvin temperature) atoms has generated a resurgence in atomic collision physics. New fields of research such as coherent control of atomic and molecular processes, quantum information and matter wave interferometry make extensive use of ultracold atoms. A major thrust of research is now to create ultracold molecules. The creation and trapping of ultracold molecules might revolutionize molecular physics and bring insight into fundamental questions of physical chemistry [1]. Spectroscopic measurements of unprecedented precision, external field control of chemical reactions, and molecular Bose-Einstein condensation may become possible, opening the door to new fundamental discoveries.

The main goal of this talk will be to describe mechanisms for controlling collision dynamics of atoms and molecules at low temperatures with electric and magnetic fields. The kinetic energy of 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 [2], stimulate forbidden electronic transitions and induce scattering resonances [3-5]. I will discuss the possibility of using electric fields to manipulate electron spin degrees of freedom of cold molecules [6] and to modify chemical reactions. I will describe interactions of molecules in a microwave laser cavity and show that microwave fields may alter the dynamics of molecular collisions at low temperatures. Finally, I will demonstrate that confining the motion of ultracold molecules to two dimensions, as can now routinely be done with ultracold atoms, may suppress inelastic collisions and chemical reactions at ultracold temperatures [7].

References:

[1] R. V. Krems, "Set for collision course", Nature Physics 3, 77 (2007).

[2] R. V. Krems, "Breaking van der Waals molecules with magnetic fields", Phys. Rev. Lett. 93, 013201 (2004).

[3] R. V. Krems, "Molecules near absolute zero and external field control of atomic and molecular dynamics", Int. Rev. Phys. Chem. 24, 99 (2005).

[4] R. V. Krems, "Controlling collisions of ultracold atoms with dc electric fields", Phys. Rev. Lett. 96, 123202 (2006).

[5] Z. Li and R. V. Krems, "Electric-field-induced Feshbach resonances in ultracold mixtures of alkali metal atoms", Phys. Rev. A 75, 032709 (2007).

[6] T. V. Tscherbul and R. V. Krems, "Controlling electronic spin-relaxation of cold molecules with electric fields", Phys. Rev. Lett. 97, 083201 (2006).