Lifetimes in 40Ca from doppler shift attenuation measurements using a Ge(Li) detector

Abstract

Measurements have been carried out of the mean lifetimes of the following five states in 40Ca. 3.90 MeV, 64±19 fsec; 5.21 MeV, 2.6 −0.7 +1.4 psec; 5.25 MeV, 190±30 fsec; 5.28 MeV 260±80 fecs; 6.29 MeV, 410±120 fsec. The Doppler shift attenuation method was used with a lithium-drifted germanium detector in a particle-gamma-ray coincidence arrangement. The technique was checked by measurements of the known lifetimes of the 1.78 MeV state in 28Si and the 1.45 MeV state in 58Ni. Accurate excitation energies have been obtained for 40Ca states. The spin of the 5.21 MeV state has been shown by a triple coincidence particle-gamma-gamma angular correlation measurement to be 0. The above data enable the parities of the states forming the triplet at 5.2 MeV to be fixed as positive. The results which imply enhancements of the electric quadrupole transitions are discussed in the light of the Gerace-Green model of a deformed 40Ca nucleus.