The two-particle stripping reaction 54Fe(3He, p 7)S6Co at E3He= 15.15 MeV was used to investigate the 7-ray transitions and to determine branching ratios, possible spin assignments and mean lifetimes of levels in 56Co up to 5.5 MeV excitation energy. Gamma-rays for both angular correlations and lifetime measurements were observed with a 43 cm 3 Ge(Li) detector in coincidence with proton-groups detected at 0 ~ The level scheme and lifetime values are compared with the predictions of various shell model calculations.

Ten gamma-ray transitions have been observed in the S4Fe(3He, n y)SNNi reaction. A new level at 3 925 ___ 10 keV is established in SaNi. Spin-parity assignments of 0 +, 4 + and 2 + are proposed for the levels at 3.925, 3.958 and 5.352 MeV, respectively. Branching ratios are given.

Abstract. Angular correlation measurements for the S4Fe(3He, n 7)S6Ni reaction were performed at E~He = 12.5 MeV. Method II of Litherland and Ferguson was used to determine the multipole mixing ratio of the 7-radiation and the spins of the excited levels at 3925 and'3956 keV. As the most probable spin assignments we deduced 4 + (3925 keV) and 0* (1, 2) (3956keV). The mixing ratio found for the 1225 keV transition from 4 + ~2 + is (5(M3/E2)= +0.21 +0.23 -0.16" This result is compared with a shell model calculation. !. IntroductionThe nucleus 5~, 9 28N128 has mainly been investigated by the (p,t) reaction on SSNi [1,2] and the (3He, n) reaction on 54Fe [-3-5]. For both reactions the experimental results concerning spin values and parities of the excited states agree in most cases. Exceptions have been found in the excitation region of 3.95, 5.4 and 6.4 MeV. For the excitation region of 3.95 MeV a spin value J==4 + resulted from the triton angular distributions and a spin value of J"= 0 + from the neutron angular distributions. In a former study [6] we found, that there exist two levels at 3925 and 3956 keV in this excitation region. In order to get some information about the spins of these levels we measured the gammaray angular distributions for the transitions from these levels to the first excited state at 2700 keV. !1. Experimental Procedure and Evaluation of DataThe 54Fe(3He, n)56Ni reaction was used to populate the 5~states. The 3He-beam of 12.5 MeV was supplied by the EN-Tandem Van de Graaff accelerator from the Max-Planck-Institut ftir Kernphysik, Heidelberg. The 3He-ions bombarded electroplated selfsupporting S4Fe-targets (2 mg/cm 2, 96~o S~Fe). Gamma-rays were detected in a Ge(Li) detector with an active volume of about 45 cm 3. The neutron detection system consisted of a 10.2 cmQ x 7.5 cm NE 213 liquid scintillator coupled to an XP 1041 photomultiplier tube which was followed by a standard pulse-shape discrimination circuit. We further used a time of flight selection, start and stop signals for the time of flight spectrum being given by the neutron and the Ge(Li) detector respectively. The neutron detector was placed at 0 ~ with respect to the beam axis while the Ge(Li) detector was positioned at five different angles between 0~. = 90 ~ and 0~, = 150 ~ The gamma-ray angular distribution measurement was supplemented by a Jz-7 coincidence experiment, for which the neutron detector was fixed at 0,=30 ~ to the beam axis. Every run (including five angles) was started with a new target, At the end of every run the target activity amounted to 25~o of the single counting rate. Changing the target with every run should not influence the angular distribution, because differences between targets, such as thickness and degree of oxidation, should have influenced all five angles in the same way. Even the relative intensities of the peaks should not be touched by the change of the targets, as the particles have a mean energy loss of about 0.5 MeV, and therefore the cross section is averaged over a wide range of energy...

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Angular correlation measurements for the 5SNi(p, p')~) reaction were performed at Ep=8.1 MeV. Method II of Litherland and Ferguson was used to determine multipole mixing ratios of the ?-radiation and spins of most of the excited levels up to 4.11 MeV. The results confirm for the most part recent measurements of van Patter et al. ; the 2 775 keV state was verified to have a spin of J= 2. Several discrepancies and additional information concerning the 3531, 3774, 3898 and 4108 keV levels are discussed. A spin value of J= 1 is assigned to the 3 531 keV level, clearly ruling out former assignments of 4 + and 0 +. A J= 4 assignment is proposed for the 3 774 keV state, contrary to the generally assumed value of J= 3, which these measurements do not support.