Measurement Of The Lifetime Of The 7s(2)S(1/2) State In Atomic Cesium Using Asynchronous Gated Detection

We report a measurement of the lifetime of the cesium 7s(2)S(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(2)S(1/2) ground state, and detect the 1.47-mu m photons from the spontaneous decay of the 7s(2)S(1/2) to the 6p(2)P(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(2)S(1/2) lifetime of 48.28 +/- 0.07 ns, 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.