Abstract
States with excitation energy > 15 MeV populated in the reaction
12C(
16O, αγ)
24Mg have been studied using a total energy γ-ray spectrometer for
E
lab(
16
O)
between 40 and 67 MeV. A previously unknown state has been identified at 16.904 ± 0.003 MeV with
Γ
γ
/
Γ=0.13±0.02, mean lifetime <10 fs, a predominant γ-decay branch to the yrast (8
+) state at 11.86 MeV and possible un-natural parity. These measurements also show that all other states produced in this excitation energy region have Γ
γ/Γ less than 0.02. Possible points of correspondence between the observed properties of the 16.9 MeV level and the predictions of shell model calculations are noted.