First measurement of the 31P(3He,t)31S reaction: A study of the thermonuclear 30P(p,γ)31S reaction rate
Abstract
The non-selective 31P(3He,t)31S reaction has been studied for the first time using 20- and 25-MeV 3He beams from the tandem Van de Graaff accelerator at Yale University's Wright Nuclear Structure Laboratory. The Yale Enge magnetic spectrograph has been used to momentum-analyze reaction products; a position-sensitive ionization drift chamber backed by a scintillator at the focal plane has been used to identify tritons and measure the excitation energies of corresponding states in 31S. Proton branching ratios and spins of 30P+p resonances have also been constrained by measuring the angular correlations of decay protons in coincidence with the tritons using the Yale Lamp Shade Array of silicon strip detectors. The 31S energy-level scheme has been considerably extended and refined above the proton threshold of 613 3 ke V, and the new information has been used to calculate the thermonuclear 30P(p,γ)31S reaction rate up to T = 10 GK. Most importantly, the existence of new resonances at Ecm. = 194.0(25) and 266.4(27) keV has been deduced which should have a significant impact on ONe nova nucleosynthesis and the classification of presolar ONe nova grains. It is recommended that these resonances be targeted in future direct measurements of the 30P(p, γ)31S reaction using radioactive 30P ion beams. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlikeLicence.