Excitation Energy and Lifetime of theO157276-keV State

An accurate determination of the energy of the sixth excited state in ${\mathrm{O}}^{15}$ has been carried out because of the proximity of this level to the proton binding energy and the resulting possibility of its importance in the stellar formation of ${\mathrm{O}}^{15}$. Gamma rays from this state occurring in the ${\mathrm{N}}^{14}(d, n){\mathrm{O}}^{15}$ reaction at $E_d=3.2\mathrm{}$ MeV were measured by means of a Ge(Li) detector at 90° to the beam. The transition leading to the (5241.3±0.5)-keV level of ${\mathrm{O}}^{15}$ is found to have an energy of 2034.7±0.3 keV. Thus the ${\mathrm{O}}^{15}$ level in question has an energy of 7276.0±0.6 keV, which is 16.8±1.3 keV below the proton binding energy of 7292.8±1.2 keV. From a measurement at 0° to the beam the 0°-90° Doppler shift of the 2035-keV gamma ray is found to be 2.3±0.4 keV. For a very short lifetime the expected Doppler shift is 14.4±1.3 keV. The observed shift corresponds to a mean lifetime of (1.25±0.3)×${10}^{-12\mathrm{}}$ sec for the 7276-keV state of ${\mathrm{O}}^{15}$.