title: Doppler cooling and trapping on forbidden transitions.
abstract: Ultracold atoms at temperatures close to the recoil limit have been achieved by extending Doppler cooling to forbidden transitions. A cloud of (40)Ca atoms has been cooled and trapped to a temperature as low as 6 microK by operating a magnetooptical 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 precooled atoms from a standard magnetooptical trap have been transferred to the ultracold trap. Monte Carlo simulations of the cooling process are in good agreement with the experiments.
authors.affiliation: Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Binnewies
authors.forename: G
authors.initials: G
authors.lastname: Wilpers
authors.forename: U
authors.initials: U
authors.lastname: Sterr
authors.forename: F
authors.initials: F
authors.lastname: Riehle
authors.forename: J
authors.initials: J
authors.lastname: Helmcke
authors.forename: T E
authors.initials: TE
authors.lastname: Mehlstäubler
authors.forename: E M
authors.initials: EM
authors.lastname: Rasel
authors.forename: W
authors.initials: W
authors.lastname: Ertmer