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Doppler cooling and trapping on forbidden transitions

T. Binnewies·G. Wilpers·U. Sterr·F. Riehle·J. Helmcke·T. E. Mehlstäubler·E. M. Rasel·W. Ertmer
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Abstract

Ultracold atoms at temperatures close to the recoil limit have been achieved by extending Doppler cooling to forbidden transitions. A cloud of ^40Ca atoms has been cooled and trapped to a temperature as low as 6 μK by operating a magneto-optical trap on the spin-forbidden intercombination transition. Quenching the long-lived excited state with an additional laser enhanced the scattering rate by a factor of 15, while a high selectivity in velocity was preserved. With this method more than 10% of pre-cooled atoms from a standard magneto-optical trap have been transferred to the ultracold trap. Monte-Carlo simulations of the cooling process are in good agreement with the experiments.

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T. Binnewies, G. Wilpers, U. Sterr, F. Riehle, J. Helmcke, T. E. Mehlstäubler, E. M. Rasel, W. Ertmer. 2001-05-21. Doppler cooling and trapping on forbidden transitions. https://doi.org/10.1103/physrevlett.87.123002

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