Bradley, C.C.Sackett, C.A.Tollett, J.J.Hulet, R.G.2015-03-302015-03-301995Bradley, C.C., Sackett, C.A., Tollett, J.J., et al.. "Evidence of Bose-Einstein Condensation in an Atomic Gas with Attractive Interactions." <i>Physical Review Letters,</i> 75, no. 9 (1995) American Physical Society: 1687-1690. http://dx.doi.org/10.1103/PhysRevLett.75.1687.https://hdl.handle.net/1911/79442Evidence for Bose-Einstein condensation of a gas of spin-polarized 7Li atoms is reported. Atoms confined to a permanent-magnet trap are laser cooled to 200 μK and are then evaporatively cooled to lower temperatures. Phase-space densities consistent with quantum degeneracy are measured for temperatures in the range of 100 to 400 nK. At these high phase-space densities, diffraction of a probe laser beam is observed. Modeling shows that this diffraction is a sensitive indicator of the presence of a spatially localized condensate. Although measurements of the number of condensate atoms have not been performed, the measured phase-space densities are consistent with a majority of the atoms being in the condensate, for total trap numbers as high as 2×10˄5 atoms. For 7Li, the spin-triplet s-wave scattering length is known to be negative, corresponding to an attractive interatomic interaction. Previously, Bose-Einstein condensation was predicted not to occur in such a system.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlehttp://dx.doi.org/10.1103/PhysRevLett.75.1687