Measurement of the lifetime of the \(7s^2S_{1/2} \) state in atomic cesium using asynchronous gated detection

We report a measurement of the lifetime of the cesium \(7s\,^2S_{1/2}\) state using time-correlated single-photon counting spectroscopy in a vapor cell. We excite the atoms using a Doppler-free two-photon transition from the \(6s\,^2S_{1/2}\) ground state, and detect the 1.47\(\mu\)m photons from the spontaneous decay of the \(7s\,^2S_{1/2}\) to the \(6p\,^2P_{3/2}\) state. We use a gated single photon detector in an asynchronous mode, allowing us to capture the fluorescence profile for a window much larger than the detector gate length. Analysis of the exponential decay of the photon count yields a \(7s\,^2S_{1/2}\) lifetime of 48.28\(\pm\)0.07ns, an uncertainty of 0.14%. These measurements provide sensitive tests of theoretical models of the Cs atom, which play a central role in parity violation measurements.