Abstract

Atomic hydrogen has been investigated in magnetostatic traps down to temperatures below the optical recoil limit for Lyman-a radiation (0.6 mK). As it is relatively straightforward to trap large numbers of H atoms and to achieve “high" densities (n > 10¹² cm⁻³), optical thickness is an important aspect in most optical experiments based on one-photon transitions. Thus far, optical investigations of trapped H were only done using pulsed VUV radiation at the Lyman-α transition (121.6 nm). The temperature and density of the samples is determined by optical spectroscopy. A report is given of optical (Doppler) cooling with pulsed light in the optically thick regime and in the inhomogeneous field of a Ioffe quadrupole trap. We also address evaporative cooling, both light-induced evaporation (LIE) and collision induced evaporation to temperatures below the optical recoil limit. The experiments show that during evaporation, non-thermal density distributions may easily arise in shallow traps.

© 1994 IEEE