High-Flux Cold Ytterbium Atomic Beam Source Using Two-Dimensional Laser Cooling with Intercombination Transition

We demonstrate a high-flux and low transverse temperature atomic beam of ytterbium by applying two-dimensional cooling using the ${}^1{\mathrm{S}}_0\text{-}{}^3{\mathrm{P}}_1$ intercombination transition to the cold atomic beam produced by the dipolar-allowed ${}^1{\mathrm{S}}_0\text{-}{}^1{\mathrm{P}}_1$ transition. The optimized transverse temperature of $11\pm 9\mu \mathrm{K}$ and an atomic flux of $(7.5 \pm 1.0) \times 10^8,$\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{m}\mathrm{s}\mathrm{/}\mathrm{s}$$ are obtained for the atomic beam whose longitudinal velocity is $30\mathrm{m}\mathrm{/}\mathrm{s}$. The transverse temperature is maintained below $23\mu \mathrm{K}$, while the flux is above $6.5 \times 10^8,$\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{m}\mathrm{s}\mathrm{/}\mathrm{s}$$inthelongitudinalvelocityrangeof$22 - 30,$\mathrm{m}\mathrm{/}\mathrm{s}$$. We also discuss the feasibility of further narrowing the transverse momentum width to less than the recoil momentum using the momentum-selective optical transition between the ground state and the long-lived metastable state. The transverse momentum width of our atomic beam, which is narrower than 5.7 times the recoil momentum, is a good starting point for the proposed method.