Laser spectroscopy of the 4s4p(3) P-2-4s3d(1) D-2 transition on magnetically trapped calcium atoms

Laser excitation of the 4s4p(3) P-2-4s3d(1) D-2 transition in atomic calcium has been observed and the wavelength determined to 1530.5298(6) nm. The metastable 4s4p(3) P-2 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 4s(2) S-1(0)-4s4p(1) P-1 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 P-3(2) atoms back up to the 4s3d(1) D-2 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 4s3d(1) D-2-4s5p(1) P-1 transition. In the present experiment, we detected about 4.5 x 10(4) trapped P-3(2) atoms, a relatively low atom density, and measured a lifetime of approximately 1 s, which is limited by background collisions.