Laser spectroscopy of the 4s4p3P₂4s3d1D₂ transition on magnetically trapped calcium atoms

Laser excitation of the 4s4p3P₂4s3d1D₂ transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable 4s4p3P₂ atoms were magnetically trapped in the quadrupole magnetic field of a magneto-optical trap. This state represents the only "loss" channel for the calcium atoms when laser cooled on the 4s21S₀4s4p1P₁ transition. A rate equation model shows that an order of magnitude more atoms are trapped in this state compared with those taking part in the main cooling cycle. Excitation of the 3P₂ atoms back up to the 4s3d1D₂ state provides a means of accessing these atoms. Efficient repumping is achieved if the 1530-nm laser is used in conjunction with a 672-nm laser driving the 4s3d1D₂4s5p1P₁ transition. In the present experiment, we detected about 4.5×104 trapped 3P₂ atoms, a relatively low atom density, and measured a lifetime of approximately 1 s, which is limited by background collisions.