Abstract
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 105 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 1×1012 cm−3.
Highlights
Avid interest in cold molecules arises from their potential utility in diverse areas of physics
Cold molecules are employed in studies of the temporal variation of fundamental constants [1, 2] and in searches for a permanent electric dipole moment of the electron
Techniques to increase molecular phase space densities through collisions benefit from increased confinement times, as efficient cooling requires sufficient time for molecule populations to thermalize to the temperature of the refrigerant [15, 14] or to rethermalize [16, 18, 17]
Summary
Avid interest in cold molecules arises from their potential utility in diverse areas of physics. The spontaneous radiative decay of molecules in rovibrationally excited levels is directly and most precisely measured by observing the temporal evolution of excited state populations [13, 12] These transitions, typically having lifetimes of several milliseconds, can be monitored when dilute samples of molecules are confined in free space using electromagnetic fields. To dissipate the translational and rotational energy of the molecules we produce from our room temperature source, we require helium densities of approximately 1×1015 cm−3. At these densities, the molecule trap lifetime is determined by the competing effects of diffusion and spin depolarization. Trap evaporation has a roughly exponential dependance on both the
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