Optimizing the production of metastable calcium atoms in a magneto-optical trap

We investigate the production of long-lived metastable (4³ P ₂ ) calcium atoms in a magneto-optical trap (MOT) operating on the 4¹ S ₀ ?4¹ P ₁ transition at 423 nm. For excited 4¹ P ₁ atoms a weak decay channel into the triplet states 4³ P ₂ and 4³ P ₁ exists via the 3¹ D ₂ state. The undesired 4³ P ₁ atoms decay back to the ground state within 0.4 ms and can be fully recaptured if the illuminated trap volume is sufficientlylarge. We obtain a flux of above 10¹⁰ atoms/s into the 4³ P ₂ state. We find that our MOT lifetime of 23 ms is mainly limited by this loss channel, and thus the 4³ P ₂ production is not hampered by inelastic collisions. If we close the loss channel by repumping the 3¹ D ₂ atoms with a 671 nm laser back into the MOT cycling transition, a non-exponential 72 ms trap decay is observed, indicating the presence of inelastic two-body collisions between 4¹ S ₀ and 4¹ P ₁ atoms. Received: 10 July 2001 / Revised version: 22 October 2001 / Published online: 23 November 2001