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arXiv:0802.1662 · Physical Review A

Magnetic trapping of atomic nitrogen (N14) and cotrapping of NH (XΣ−3)

Matthew T. Hummon, Wesley C. Campbell, Hsin-I Lu, Edem Tsikata, Y. H. Wang, John M. Doyle

Published Nov 12, 2008• 43 citations
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Abstract

We observe magnetic trapping of atomic nitrogen $(^{14}\mathrm{N})$ and cotrapping of ground-state imidogen ($^{14}\mathrm{N}\mathrm{H}$, $X\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{\ensuremath{-}}$). Both are loaded directly from a room-temperature beam via buffer gas cooling. We trap approximately $1\ifmmode\times\else\texttimes\fi{}{10}^{11}$ $^{14}\mathrm{N}$ atoms at a peak density of $5\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $550\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$. The $12\ifmmode\pm\else\textpm\fi{}4\phantom{\rule{0.3em}{0ex}}\mathrm{s}$ $1∕e$ lifetime of atomic nitrogen in the trap is consistent with a model for loss of atoms over the edge of the trap in the presence of helium buffer gas. Cotrapping of $^{14}\mathrm{N}$ and $^{14}\mathrm{N}\mathrm{H}$ is accomplished, with ${10}^{8}$ NH trapped molecules at a peak density of ${10}^{8}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$.

DOI
10.1103/physreva.78.050702

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We report on the buffer-gas cooling and trapping of CrH and MnH molecules in a magnetic quadrupole trap with densities on the order of ${10}^{6}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at a temperature of 650mK650\phantom{\rule{0.3em}{0ex}}\mathrm{mK}650mK. Storage times of up to 180ms180\phantom{\rule{0.3em}{0ex}}\mathrm{ms}180ms have been observed, corresponding to a 20-fold lifetime enhancement with respect to the field-free diffusion through the 3He^{3}\mathrm{He}3He buffer-gas. Using Monte Carlo trajectory simulations, inelastic molecule-3He^{3}\mathrm{He}3He collision cross sections of $1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ and $3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$ are extracted for CrH and MnH, respectively. Furthermore, elastic molecule-3He^{3}\mathrm{He}3He collision cross sections of $1.4(\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$ are determined for both species. We conclude that the confinement time of these molecules in a magnetic trapping field is limited by inelastic collisions with the helium atoms leading to Zeeman relaxation.
We describe a method for loading paramagnetic atoms or molecules into a magnetic trap. A 3He^{3}\mathrm{He}3He buffer gas is employed to thermalize atoms or molecules to a temperature of approximately 240 mK, lower than the depth of the trap. A model is described that indicates an initial loading density of approximately 1013{10}^{13}1013 ${\mathrm{cm}}^{\ensuremath{-}3}$. Once loading has taken place the buffer gas is removed by cryopumping. Evaporative cooling can then be applied to further lower the temperature and increase the density of the trapped sample.