MEAN LIFETIMES AND BRANCHING RATIOS OF LOW-LYING LEVELS IN S-33

The mean lifetimes of the levels of S33 below 3.3-MeV excitation energy have been measured by the Doppler shift attenuation method. The Si30(α,n)S33 reaction was used to populate these states. SiO2 targets (enriched to 95% in Si33) evaporated onto Ni backings were bombarded with α-particles ranging in energy 5.5-9.0 MeV. γ-ray spectra were recorded with a 20-cc Ge (Li) detector at 0 °, 90 °, and 510 ° to the beam. The following mean lifetimes were found: τ(0.842-MeV level) =1.66±0.34 psec, τ(1.968)=182±22 fsec, τ(2.313)=183±25 fsec, τ(2.869)<15 fsec, τ(2.937)>4 psec, τ(2.970)=82±12 fsec, τ(3.221)<65 fsec. The branching ratios of the 2.970-MeV level were determined to be (90±5)% to the ground state and (10±5)% to the second excited state. © 1969 The American Physical Society.