Secondary laser cooling of strontium-88 atoms

Abstract

The secondary laser cooling of a cloud of strontium-88 atoms on the 1S0–3P1 (689 nm) intercombination transition captured into a magneto-optical trap has been demonstrated. We describe in detail the recapture of atoms from the primary trap operating on the strong 1S0–1P1 (461 nm) transition and determine the recapture coefficient κ, the number of atoms, and their temperature in the secondary trap as a function of experimental parameters. A temperature of 2 µK has been reached in the secondary trap at the recapture coefficient κ = 6%, which confirms the secondary cooling efficiency and is sufficient to perform metrological measurements of the 1S0–3P1 (698 nm) clock transition in an optical lattice.