  The ability to directly measure the momentum distribution of quantum gases is
both unique to these systems and pivotal in extracting many other important
observables. Here we use Raman transitions to measure the momentum distribution
of a weakly-interacting Fermi gas in a harmonic trap. For narrow atomic
dispersions, momentum and energy conservation imply a linear relation between
the two-photon detuning and the atomic momentum. We detect the number of atoms
transferred by the Raman beams using sensitive fluorescence detection in a
magneto-optical trap. We employ this technique to a degenerate
weakly-interacting Fermi gas at different temperatures. The measured momentum
distributions match theoretical curves over two decades, and the extracted
temperatures are in very good agreement with the ones obtained from a
conventional time-of-flight technique. The main advantages of our measurement
scheme are that it can be spatially selective and applied to a trapped gas, it
can be completed in a relatively short time, and due to its high sensitivity,
it can be used with very small clouds.
