Improved magneto–optical trapping of a diatomic molecule

Abstract

We present experimental results from a new scheme for magneto–optically trapping strontium monofluoride (SrF) molecules, which provides increased confinement compared to our original work. The improved trap employs a new approach to magneto–optical trapping presented by Tarbutt (2015 New J. Phys. http://dx.doi.org/10.1088/1367-2630/17/1/015007 17 http://dx.doi.org/10.1088/1367-2630/17/1/015007 ), which provided insight for the first time into the source of the restoring force in magneto–optical traps (MOTs) where the cycling transition includes dark Zeeman sublevels (known as type-II MOTs). We measure a radial spring constant $20\times $ greater than in our original work with SrF, comparable to the spring constants reported in atomic type-II MOTs. We achieve a trap lifetime ${{\tau }_{{\rm MOT}}}=136(2)$ ms, over $2\times $ longer than originally reported for SrF. Finally, we demonstrate further cooling of the trapped molecules by briefly increasing the trapping lasers’ detunings. Our trapping scheme remains a straightforward extension of atomic techniques and marks a step towards the direct production of large, dense, ultracold molecular gases via laser cooling.

Keywords

• magneto–optical trap
• molecules
• laser cooling
• trapping