Coincident high-velocity DSA lifetime measurements on excited states of Si isotopes and stopping power investigations

Abstract

Mean lives of low-lying states of 28Si, 29Si and 30Si have been measured with the coincident high-velocity DSA method by 28Si bombardment of 2H, 3H and 4He targets. The recoils with an initial velocity of about 0.048c are slowed down in Mg, Cu, Ag and Au. The emitted γ-ray Doppler patterns are observed with a Ge(Li) detector at θγ = 0° in coincidence with outgoing particles. The results are: 28Si, τm (1.78 rnMeV) = 688 ± 26 fs; 29rnSi, 420±15, 442±14, 26.6±1.6, 46±3 and 3740 ± 190 fs for states at 1.27, 2.03, 2.43, 3.07 and 3.62 MeV, respectively; 30Si, τm (2.24 MeV) = 358 + 18 fs. The deduced transition strengths are compared with shell-model calculations. Stopping powers obtained from Ziegler's effective charge parametrization are compared to experimental data. The usual DSA procedure is also reversed in the sense that a well-established mean life is used to deduce the electronic stopping power for Si ions in Mg. The result found is verified by other DSA measurements.