Measurement of the calcium ^1P_1−^1D_2 transition rate in a laser-cooled atomic beam

The efficiency of laser cooling in a thermal beam of calcium has been investigated under different cooling schemes. Special attention has been paid to analysis of the loss factor represented by the decay of atoms excited by the cooling laser to the 1P1 state into the metastable 1D2 level. The cooling scheme at a fixed laser frequency makes possible a good estimation of the branching ratio R between the decay probability from the 1P1 level to the ground 1S0 state and to the metastable 1D2 state. The measured value of (1.0 ± 0.15) × 105 seems high enough to produce only a small reduction in the cooling efficiency.