An Optical Trap for Collisional Studies on Cold Fermionic Potassium

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We report on trapping of fermionic 40K atoms in a red-detuned standing-wave optical trap, loaded from a magneto-optical trap. Typically, 10⁶ atoms are loaded at a density of 10¹2 cm-3 and a temperature of 65 microK, and trapped for more than 1 s. The optical trap appears to be the proper environment for performing collisional measurements on the cold atomic sample. In particular we measure the elastic collisional rate by detecting the rethermalization following an intentional parametric heating of the atomic sample. We also measure the inelastic two-body collisional rates for unpolarized atoms in the ground hyperfine states, through detection of trap losses.