Far-off-resonance optical trapping of atoms

We confine ⁸⁵Rb atoms in an optical dipole force trap with a very large detuning from resonance of up to 65 nm. Confinement times of 200 ms, limited only by background-gas collisions, are obtained without additional cooling. A typical trap contains 1300 atoms at a temperature of 0.4 mK and a peak density of 8×{}10¹¹ cm^-3. We measure spontaneous photon scatter rates of the trapped atoms to be less than 1.6×{}10³ s^-1, corresponding to recoil heating rates below 0.6 mK/s. The far-detuned trap confines atoms with a strong, nearly conservative optical force and negligible atomic excitation.