Measurement of p-wave threshold law using evaporatively cooled fermionic atoms

We have measured independently both s-wave and p-wave cross-dimensional the rmalization rates for ultracold K-40 atoms held in a magnetic trap. These m easurements reveal that this fermionic isotope has a large positive s-wave triplet scattering length in addition to a low temperature p-wave shape res onance. We have measured directly the p-wave threshold law which, combined with the Fermi statistics, dramatically suppresses elastic collision rates at low temperatures. In addition, we present initial evaporative cooling re sults that make possible these collision measurements and are a precursor t o achieving quantum degeneracy in this neutral, low-density Fermi system. [ S0031-9007(99)09214-5].