The decay properties of the levels in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ up to 1720.12 keV have been carefully investigated via the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p,n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ reaction at 7.3 MeV, using a Ge(Li)-NaI(Tl) anti-Compton spectrometer. Three new weak transitions from well established levels were observed. Using the Doppler-shift attenuation method the values of ${0.48}_{-0.15\mathrm{}}^{+0.32\mathrm{}}$, ≥ 1.1, ${0.11}_{-0.02\mathrm{}}^{+0.03\mathrm{}}$, ${0.63}_{-0.18\mathrm{}}^{+0.36\mathrm{}}$, ${0.35}_{-0.03\mathrm{}}^{+0.05\mathrm{}}$, ≥ 0.6, and ${0.49}_{-0.17\mathrm{}}^{+0.51\mathrm{}}$ psec were obtained for the lifetimes of the 576.47-, 829.60-, 970.25-, 1009.11-, 1114.48-, 1450.62-, and 1720.12-keV levels, respectively. The value of the stopping power of Ni, previously calibrated for Cu ions, was used for the stopping of Co ions in Fe in order to extract the lifetimes from the measured centroid shifts obtained in singles experiments. Limits for the $B\left(E2\mathrm{}\right)\mathrm{}$ and $B\left(M1\mathrm{}\right)\mathrm{}$ values of many transitions were deduced from the present lifetimes and branching ratios using previously reported limits for the multipole mixing ratios $\delta \left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$. The results are compared with recent shell model calculations and good agreement is observed.

NUCLEAR REACTIONS ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p,n\gamma )$, $E_p=7.3\mathrm{}$ MeV, enriched targets; measured $E_{\gamma }$, $I_{\gamma }$, $I_{\gamma }\left(\theta \right)$, $\Delta E_{\gamma }\left(\tau \right)$; confirmed ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ levels; deduced branching ratios, $\tau$, $B\left(E2\mathrm{}\right)\mathrm{}$ and $B\left(M1\mathrm{}\right)\mathrm{}$ values.

• Received 13 June 1974

DOI:https://doi.org/10.1103/PhysRevC.10.1407