Key points are not available for this paper at this time.
We present a new laser-cooling scheme based on velocity-selective optical pumping of atoms into a nonabsorbing coherent superposition of states. This method has allowed us to achieve transverse cooling of metastable ^4He atoms to a temperature of 2, lower than both the usual Doppler cooling limit (23) and the one-photon recoil energy (4). The corresponding de Broglie wavelength (1. 4) is larger than the atomic-transition optical wavelength.
Aspect et al. (Mon,) studied this question.