Bose-Einstein condensation of 88Sr through sympathetic cooling with 87Sr

We report Bose-Einstein condensation of 88Sr, which has a small, negative s-wave scattering length (a88=-2a0). We overcome the poor evaporative cooling characteristics of this isotope by sympathetic cooling with 87Sr atoms. 87Sr is effective in this role despite the fact that it is a fermion because of the large ground-state degeneracy arising from a nuclear spin of I=9/2, which reduces the impact of Pauli blocking of collisions. We observe a limited number of atoms in the condensate (Nmax≅104) that is consistent with the value of a88 and the optical dipole trap parameters.