Sensitive Detection of Cold Cesium Molecules Formed on Feshbach Resonances

Abstract

We observe the dynamic formation of quasibound ${\mathrm{C}\mathrm{s}}_2$ molecules near Feshbach resonances in a cold sample of atomic cesium. Using an external probe beam, more than 15 weakly coupled molecular states are detected with high sensitivity, whose collisional formation cross sections are as small as $\sigma =2\times {10}^{-16}{\mathrm{c}\mathrm{m}}^2$. By modeling the molecule formation and dissociation processes with rate equations, we conclude that at an atomic density of ${10}^{13}{\mathrm{c}\mathrm{m}}^{-3}$ and temperature of $5\mu \mathrm{K}$, more than $5(1)\times {10}^5{\mathrm{C}\mathrm{s}}_2$ molecules in a single rovibrational state coexist with ${10}^8$ Cs atoms in our trap.