Subrecoil Raman Cooling of Cesium Atoms

We use velocity-selective Raman pulses generated by two diode lasers to cool cesium atoms in 1 dimension to an r.m.s. of 1.2 mm/s. This is about 1/3 of the single-photon recoil velocity v rec = ℏk/M , where ℏk is the photon momentum and M the atom's mass. The corresponding effective temperature is a factor of 9 below the single-photon recoil temperature given by k B T rec /2 = 1/2 Mv rec 2 . Because of the high cesium mass, this temperature is only (23 ± 5) nanokelvin, the lowest 1D kinetic temperature reported to date.