New gamma-ray transitions observed in Ne-19 with implications for the O-15(alpha, gamma)(19) Ne reaction rate

摘要

The O-15(alpha, gamma)(19) Ne reaction is responsible for breakout from the hot CNO cycle in type I x-ray bursts. Understanding the properties of resonances between E-x = 4 and 5 MeV in Ne-19 is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14-and 4.20-MeV states, which have adopted spin-parities of 9/2(-) and 7/2(-) respectively. gamma-ray transitions from these states were studied using triton-gamma-gamma coincidences from the F-19(He-3, t gamma)(19) Ne reaction measured with the GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the J(pi) values are actually 7/2(-) and 9/2(-), respectively. These assignments are consistent with the values in the F-19 mirror nucleus and in contrast to previously accepted assignments.