Demonstration of a $^{6}$Li magneto-optical trap using the $2S_{1/2}\rightarrow 3P_{3/2}$ transition

We demonstrate narrow linewidth laser cooling on the $2S_{1/2}\rightarrow 3P_{3/2}$ transition of $^{6}$Li at 323 nm. Typically, magneto-optical traps (MOTs) of alkali atoms cool on the D2 transition. The linewidth of this transition determines the Doppler limit of cooling which in the case of $^{6}$Li is 140 $\mu$K, given a 5.9 MHz transition linewidth. Due to a lack of resolved hyperfine structure that prohibits polarization gradient cooling, typical Li MOTs reach minimum temperatures near 300 $\mu$K. Cooling on the $2S_{1/2}\rightarrow 3P_{3/2}$ transition, however, allows for a Doppler limit of 20 $\mu$K since the transition linewidth is only 790 kHz. We have implemented this cooling scheme and demonstrate $^{6}$Li MOT temperatures of 65 $\mu$K. The substantially decreased temperature of this MOT enhances loading of the gas into an optical trap. We present our results on the characteristics of the narrow linewidth MOT and our results on the benefits of using this cooling scheme in the preparation of a degenerate gas of fermions.