Precise Lifetime Measurement of the Cesium \(5^2D_{5/2}\) State

We measure the lifetime of the cesium \(5^2D_{5/2}\) state using a time-resolved single-photon-counting method. We excite atoms in a hot vapor cell via an electric quadrupole transition at a wavelength of \(685\,\mathrm{nm}\) and record the fluorescence of a cascade decay at a wavelength of \(852\,\mathrm{nm}\). We extract a lifetime of \(1353(5)\,\mathrm{ns}\) for the \(5^2D_{5/2}\) state, in agreement with a recent theoretical prediction. In particular, the observed lifetime is consistent with the literature values of the polarizabilities of the cesium \(6P\) states. Our measurement contributes to resolving a long-standing disagreement between a number of experimental and theoretical results.