Angular correlation and lifetime measurements in 30Si using a Ge(Li) detector

Abstract

Gamma rays from the decay of the first four excited states of 30Si have been observed with a 25 cm 3 Ge(Li) detector following the reaction 27Al(α, p) 30Si. The cascade decays of the 3.767 and 3.786 MeV states are clearly resolved. The 3.767 MeV state decays to the ground and first excited states in the ratio 38 : 62; the 3.786 MeV state decays entirely to the first excited state. The observed Doppler shifts of the gamma rays from the first four excited states indicate their respective lifetimes to be 4.6±0.5, 1.5±0.2, 1.0±0.2 and > 12 in units of 10 −13 sec. Gamma-gamma coincident angular correlations have been measured for the 3.767 and 3.786 MeV states using a 12.7 cm diam. × 15.2 cm long NaI(Tl) crystal for the second detector. The correlation for the 3.786 MeV state assigns spin zero uniquely, that for the 3.767 MeV state is consistent with spins 1, 2 or 3. Spin 3 is ruled out by the lifetime estimate and the observed branching ratio.