Lifetime of the 8.543-MeV level of 28Si

Abstract

The 25Mg(α,nγ)28Si reaction has been used in a measurement of the lifetime of the (6+), 8.543-MeV level in 28Si. The incident α-particle energy was chosen to be close to the threshold energy of the reaction, so that the directions of the recoiling nuclei were confined to a narrow cone. The 0°–90° attenuated Doppler shift of the 3.926-MeV gamma ray from the 8.543-MeV to the 4+, 4.167-MeV level was measured with two Ge(Li) counters. The lifetime of the 8.543-MeV level was measured to be 58 ± 12 fs.