Magneto-optical trapping forces for atoms and molecules with complex level structures

M. R. Tarbutt

doi:10.1088/1367-2630/17/1/015007

paper

Magneto-optical trapping forces for atoms and molecules with complex level structures

arXiv:1409.0244 · doi:10.1088/1367-2630/17/1/015007

Abstract

Laser cooling and magneto-optical trapping of molecules typically involves multiple transitions driven by several laser frequencies. We analyze how magneto-optical trapping forces depend on the angular momenta, $F_{l}$ and $F_{u}$ , and the g-factors, $g_{l}$ and $g_{u}$ , of the lower and upper states. When $F_{l} > F_{u}$ the polarizations must be reversed relative to cases where $F_{u} \geq F_{l}$ . The correct choice of circular polarization depends on the sign of $g_{u}$ but not on the sign of $g_{l}$ . If $g_{u}$ is zero there is no trapping force, and the trapping force is very weak whenever $g_{u}$ is small compared to $g_{l}$ , which it usually is when the cooling transition is the $^{2} Σ$ to $^{2} Π_{1/2}$ transition of a molecule. For some molecules, mixing of the excited $^{2} Π_{1/2}$ state with a nearby $^{2} Σ$ excited state can greatly increase $g_{u}$ , leading to stronger trapping forces. A strong trapping force can also be produced by rapidly and synchronously reversing both the magnetic field and the laser polarizations. We simulate a recent experiment on magneto-optical trapping of SrF molecules, and suggest that an alternative choice of laser beam polarizations will strengthen the trapping force.

20 pages, 9 figures. Minor changes to text. Part (c) added to figure 1 and first line of table 2 revised

Magneto-optical trapping forces for atoms and molecules with complex level structures

Abstract

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