Triple Correlations in theFe56(p,γγ)Co57Reaction

Approximately seventy resonances were observed for the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p,\gamma ){}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ reaction in the range of proton energy from 1300 to 1800 keV. Gamma-ray energy measurements performed with scintillation and lithium-drift silicon spectrometers yield 6.040±0.030 MeV for the $Q$ value of the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p,\gamma ){}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ reaction and show the existence of intermediate states in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ at 1.381±0.010, 1.506±0.020, 1.760±0.020, 1.921±0.020, 2.136±0.020, 2.60±0.03, 2.74±0.03, 2.80±0.03, 2.88±0.03, 3.11±0.03, 3.18±0.03, 3.27±0.03, and 3.52±0.03 MeV. Triple-correlation measurements performed with a double sum-coincidence spectrometer permit $J^{\pi }$ assignments of ${\frac{3}{2}}^{-}$, ${\frac{5}{2}}^{-}$, ${\frac{5}{2}}^{-}$, and ${\frac{5}{2}}^{+}$ to the intermediate states in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ at 1.38, 1.76, 1.92, and 2.14 MeV, respectively. These measurements were performed at resonance energies of 1525, 1598, 1622, 1637, 1645, and 1800 keV, where the capturing states at the 1637- and 1800-keV resonances are assigned a $J^{\pi }$ value of ${\frac{5}{2}}^{+}$, and for the others $J^{\pi }$ is ${\frac{3}{2}}^{-}$. Ambiguities exist for the $\frac{E2\mathrm{}}{M1\mathrm{}}$ amplitude ratios for all of the mixed secondary gamma-ray transitions observed in these studies. All measurements were in agreement with the established value of ${\frac{7}{2}}^{-}$ for the ground state of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$.