Prospects for a narrow line MOT in YO

In addition to being suitable for laser cooling and trapping in a magneto-optical trap (MOT) using a relatively broad transition, the molecule YO possesses a narrow-line transition. This forbidden transition between the and states has linewidth kHz. After cooling in a MOT on the 614 nm to (orange) transition, the narrow 690 nm (red) transition can be used to further cool the sample, requiring only minimal additions to the first stage system. We estimate that the narrow line cooling stage will bring the temperature from ?1 mK to ?10 ?K, significantly advancing the frontier on direct cooling achievable for molecules.