Doppler cooling on a forbidden transition is studied experimentally and numerically. By quenching the upper level of the cooling transition, the scattering rate is increased, and 106 40Ca atoms have been cooled and trapped in a magneto-optical trap to temperatures of down to 6 μK. A model is developed that describes the cooling method by rate equations. Based on the model, Monte Carlo simulations are performed that show good agreement with the experimental results. Possibilities of reaching high densities and low temperature by optimizing the parameters during the cooling phase are discussed, and the benefit of these ultracold atoms for the accuracy and stability of optical frequency standards is demonstrated.
© 2003 Optical Society of America
Uwe Sterr, Tomas Binnewies, Carsten Degenhardt, Guido Wilpers, Jürgen Helmcke, and Fritz Riehle, "Prospects of Doppler cooling on forbidden lines," J. Opt. Soc. Am. B 20, 985-993 (2003)