Prospects for Bose-Einstein condensation of metastable neon atoms

The calculated upper limit ${\mathcal{K}}_i^{\mathrm{pol}}<~{10}^{-14}{\mathrm{cm}}^3/\mathrm{s}$ of the rate constant for suppressed ionization in a gas of metastable $\mathrm{Ne}{(}^3{\mathrm{P}}_2)$ atoms in the fully aligned $|{J=2,m}_J=2\mathrm{}〉$ state is used as input to investigate the prospects for achieving Bose-Einstein condensation (BEC). The heating rate of the trap population by secondary collisions of the hot products of the process of ionization—i.e., ground-state atoms, ions, and dimer-ions—with cold trapped metastable atoms is discussed in terms of a semiclassical model. An important step lies in limiting the depth of the magnetic trap to a value of a few millikelvin, to limit the range of small-angle scattering that contributes to heating. Also, a tight radial confinement reduces the probability for secondary collisions. At a trap depth of 10 mK, a radial dimension of $3\mu \mathrm{m},$ and a density of $2\times {10}^{13}{\mathrm{cm}}^{-3}$ the heating rate is $1.4\mu \mathrm{K}/\mathrm{s},$ which should be compared to the transition temperature to BEC of $0.6\mu \mathrm{K}.$ The collisional heating is dominated by ion—metastable-atom collisions, due to their long-range charge-induced dipole interaction. Keeping the evaporative cooling switched on at ${T=T}_C$ reduces the heating a hundredfold. Using a bright beam of laser cooled neon atoms, an initial population of $>~{10}^{10}$ atoms can be loaded into a magneto-optical trap in one second. Tight magnetic traps are easy to achieve for metastable neon atoms, due to their magnetic moment of $3{\mu }_B.$ We conclude that achieving BEC is feasible for metastable neon. This also holds for triplet metastable helium, once the loading rate of traps has been improved. Finally, the semiclassical model used for calculating the heating rate is applicable to a wide range of inelastic collisions in trapped alkali gases and/or collisions with background gas.