Magneto-optical trapping and cooling of strontium atoms down to the photonrecoil temperature

We report narrow-line laser cooling and trapping of strontium atoms down to the photon recoil temperature. Sr-88 atoms precooled by the broad S-1(0)-P -1(1) transition at 461 nm were further cooled in a magneto-optical trap us ing the spin-forbidden transition S-1(0)-P-3(1) at 689 nm. We have thus obt ained an atomic sample with a density over 10(12) cm(-3) and a minimum temp erature of 400 nK, corresponding to a maximum phase space density of 10(-2) which is 3 orders of magnitude larger than the value that has been obtaine d by magneto-optical traps to date. This scheme provides us an opportunity and system to study quantum statistical properties of degenerate fermions a s well as bosons. [S0031-9007(98)08352-5].