MAGNETOOPTICAL TRAPPING AND ULTRACOLD COLLISIONS OF POTASSIUM ATOMS

We present measurements of loading and loss rates for a vapor-cell optical trap of the two naturally occurring potassium isotopes K-39 and K-41. The unresolved excited-state hyperfine structure makes trapping of K fundamentally different from trapping of the other alkalis and leads to an enhanced loading rate. We measure the loading rate as a function of laser intensity, beam size, and detuning and find that the results are in reasonable agreement with a simple rate-equation model for the loading process. The dependence of the loss rate on trapped-atom density determines the contribution to the loss rates from excited-state collisions. We find a substantial difference between the collisional loss rates for the two isotopes.