Lifetime measurement of the first excited $5/2^{+}$ state in ¹³³Cs using NaI(Tl) and LaBr₃(Ce) detectors

We report a new high-precision lifetime measurement of the first excited $5/2^{+}$ state of ¹³³Cs using NaI(Tl) and LaBr₃(Ce) detectors. The time difference between the coincident decays of two successive states was measured using fast-timing electronics. The 356-keV ($1/2^{+}\to 5/2^{+}$) gamma transition was tagged by the successive 81-keV ($5/2^{+}\to 7/2^{+}$) transition of ¹³³Cs. The half-life of the first excited $5/2^{+}$ ¹³³Cs state was measured as $T_{1/2}=6.283\pm 0.004$ (stat.) $\pm 0.011$(syst.) ns.