REDUCTION OF LIGHT-ASSISTED COLLISIONAL LOSS RATE FROM A LOW-PRESSURE VAPOR-CELL TRAP

We have demonstrated an order of magnitude increase in the number and in the lifetime of magneto-optically trapped Rb87 atoms collected from a low-pressure vapor. The improvement results from the reduction of light-assisted collision losses and is achieved by shelving the atomic population into the lower hyperfine ground state. Large fractional populations of the lower hyperfine ground state have been obtained by blocking the hyperfine repumping light in the region of the trapped atoms and by application of laser light that optically pumps the atoms into that state. We have observed trap lifetimes in excess of 700 s at our highest vacuum levels. At the rubidium pressure that maximizes the product of the number and lifetime of trapped atoms we observe a lifetime of 240 s with 5×107 trapped atoms, under conditions for which an ordinary magneto-optical trap has a lifetime of only 14 s with 3×106 atoms. © 1994 The American Physical Society.