| Popis: |
A study has been made of states in ${\mathrm{O}}^{16}$ between 7.2- and 11.5-Mev excitation which belong to the sequence ${0}^{\ensuremath{-}}$, ${1}^{+}$, ${2}^{\ensuremath{-}}$, ${3}^{+}$,... (even angular momentum and odd parity, and vice versa). These states cannot break up into ${\mathrm{C}}^{12}$+$\ensuremath{\alpha}$ but must decay by $\ensuremath{\gamma}$ emission. The $\ensuremath{\gamma}$ rays from the ${\mathrm{F}}^{19}(p, \ensuremath{\alpha}\ensuremath{\gamma}){\mathrm{O}}^{16}$ and ${\mathrm{N}}^{15}(d, n\ensuremath{\gamma}){\mathrm{O}}^{16}$ reactions were studied at bombarding energies up to 6.0 and 5.08 Mev, respectively, using a three-crystal pair spectrometer and other scintillation counters. The design, resolution, and efficiency of the three-crystal pair spectrometer are given. The ground state transition from the ${2}^{\ensuremath{-}}$, 8.87-Mev state was observed to have 0.07\ifmmode\pm\else\textpm\fi{}0.02 the intensity of the 2.73-Mev cascade transition to the ${3}^{\ensuremath{-}}$, 6.14-Mev state. A state was found at 10.98\ifmmode\pm\else\textpm\fi{}0.04 Mev which decays predominantly to the ${1}^{\ensuremath{-}}$, 7.12-Mev state. No $\ensuremath{\gamma}$ rays resulting from the decay of this state to other states of ${\mathrm{O}}^{16}$ were observed. The angular correlation of the 3.86- and 7.12-Mev $\ensuremath{\gamma}$ rays shows a positive anisotropy of approximately 1. These results suggest a ${0}^{\ensuremath{-}}$ spin and parity assignment for the 10.98-Mev state. The predictions of the alpha-particle and shell models of ${\mathrm{O}}^{16}$ are compared with these results. |
