Magnetic trapping of NH molecules with 20 s lifetimes

Buffer gas cooling is used to trap NH molecules with 1/ e lifetimes exceeding 20 s. Helium vapor generated by laser desorption of a helium film is employed to thermalize 10 5 molecules at a temperature of 500 mK in a 3.9 T magnetic trap. Long molecule trapping times are attained through rapid pumpout of residual buffer gas. Molecules experience a helium background gas density below 1 × 10 12 cm −3 .