A System To Measure Isomeric State Half-Lives In The 10 Ns To 10 Mu S Range

The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe gamma-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of Sao Paulo with the measurement of two known isomeric states: Fe-54, 10(+) state (E = 6527.1 (11) keV, T-1/2 = 364(7) ns) and the 5/2(+) state of F-19 (E = 197.143 (4) keV, T-1/2 = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed gamma-gamma coincidence method. The measured half-life for the 10(+) state was T-1/2 = 365(14) ns and for the 5/2(+) state, 100(36) ns. (C) 2014 AIP Publishing LLC.