Evidence for the existence of the astrophysically important 6.40-MeV state of 31S

D. Irvine, McMaster University
A. A. Chen, McMaster University
A. Parikh, Universitat Politècnica de Catalunya
K. Setoodehnia, McMaster University
T. Faestermann, Fakultät für Physik, Technische Universität München
R. Hertenberger, Ludwig-Maximilians-Universität München
H. F. Wirth, Ludwig-Maximilians-Universität München
V. Bildstein, University of Guelph
S. Bishop, Fakultät für Physik, Technische Universität München
J. A. Clark, Argonne National Laboratory
C. M. Deibel, Argonne National Laboratory
J. Hendriks, The University of Western Ontario
C. Herlitzius, Fakultät für Physik, Technische Universität München
R. Krücken, Fakultät für Physik, Technische Universität München
W. N. Lennard, The University of Western Ontario
O. Lepyoshkina, Fakultät für Physik, Technische Universität München
R. Longland, Universitat Politècnica de Catalunya
G. Rugel, Fakultät für Physik, Technische Universität München
D. Seiler, Fakultät für Physik, Technische Universität München
K. Straub, Fakultät für Physik, Technische Universität München
C. Wrede, University of Washington

Abstract

Proton-unbound excited states of 31S have been populated with the 32S(d,t)31S reaction at a beam energy of 24 MeV. Tritons corresponding to 31S states with Ex(31S)≈6.3-7.1 MeV were momentum analyzed with a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph at six angles ranging from θlab=15 â̂̃ to 58.5â̂̃. We report a statistically significant detection of an astrophysically important state at Ex(31S)=6402 (2) keV, whose existence as a third state in this region has been under debate. Using updated A=31 nuclear structure information, we present a new set of proposed 31S-31P mirror assignments for 31S, in which this state is tentatively assigned a spin of 7/2. This level, corresponding to a 30P + p resonance at 271 keV, is likely to have a significant influence on the 30P(p,γ)31S reaction rate in explosive hydrogen burning in classical novae. © 2013 American Physical Society.