Study of astrophysically important resonant states in 30 S using the 32S(p,t)30 S reaction

¹ Department of Physics & Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada
² Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
³ Department of Physics & Astronomy, University of Western Ontario London, ON N6A 3K7, Canada
⁴ Wright Nuclear Structure Laboratory, Yale University, New Haven, CT, 06520, USA
⁵ Department of Physics, University of Washington, Seattle, WA 98195-1560, USA

^a e-mail: setoodk@mcmaster.ca

Abstract

A small fraction (< 1%) of presolar SiC grains is suggested to have been formed in the ejecta of classical novae. The ²⁹P(p,γ)³⁰S reaction plays an important role in understanding the Si isotopic abundances in such grains, which in turn provide us with information on the nature of the probable white dwarf progenitor’s core, as well as the peak temperatures achieved during nova outbursts, and thus the nova nucleosynthetic path. The ²⁹P(p,γ)³⁰S reaction rate at nova temperatures is determined by two low-lying 3⁺ and 2⁺ resonances above the proton threshold at 4399 keV in ³⁰S. Despite several experimental studies in the past, however, only one of these two states has only been observed very recently. We have studied the ³⁰S nuclear structure via the ³²S(p,t) ³⁰S reaction at 5 laboratory angles between 9° to 62°. We have observed 14 states, eleven of which are above the proton threshold, including two levels at 4692.7 ± 4.5 keV and 4813.8 ± 3.4 keV that are candidates for the 3⁺ and the previously “issing” 2⁺ state, respectively.