Lifetime measurement of ultracold caesium Rydberg states

We measure the nS and nD (n = 30-40) state lifetimes of caesium Rydberg atoms in a conventional magneto-optical trap using the field ionization technique, which is consistent with the existing theoretical model through suppressing collisions and super-radiance effects. We also investigate variation of the lifetimes with densities of Rydberg atoms by changing the pulse energy of the dye laser. The results indicate that collisions and super-radiance effects have a large influence on the accuracy of lifetime measurement at high densities of Rydberg atoms.