title: A system to measure isomeric state half-lives in the 10 ns to 10 μs range.
abstract: 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 γ-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 São Paulo with the measurement of two known isomeric states: (54)Fe, 10(+) state (E = 6527.1 (11) keV, T(1/2) = 364(7) ns) and the 5/2(+) state of (19)F (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 γ-γ 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.
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: D L
authors.initials: DL
authors.lastname: Toufen
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: P R P
authors.initials: PR
authors.lastname: Allegro
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: N H
authors.initials: NH
authors.lastname: Medina
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: J R B
authors.initials: JR
authors.lastname: Oliveira
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: E W
authors.initials: EW
authors.lastname: Cybulska
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: W A
authors.initials: WA
authors.lastname: Seale
authors.affiliation: Fluminense Federal University, 24220-900 Niterói, Rio de Janeiro, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Linares
authors.affiliation: Universitary Center of FEI, 09850-901 São Bernardo do Campo, São Paulo, Brazil.
authors.forename: M A G
authors.initials: MA
authors.lastname: Silveira
authors.affiliation: Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: R V
authors.initials: RV
authors.lastname: Ribas