Relative proton and gamma widths of astrophysically important states in 30S studied in the beta-decay of 31Ar

TL;DR

This study introduces a new method to determine the ratio of proton to gamma widths of resonances in 30S, crucial for astrophysical reaction rates, using beta decay data from 31Ar at CERN, providing first experimental limits.

Contribution

The paper presents an innovative approach to measure proton and gamma partial widths of 30S resonances via beta decay of 31Ar, offering new experimental constraints for astrophysical models.

Findings

First experimental limits on proton to gamma width ratios in 30S resonances.

Identification of a 4688 keV level and upper limits on widths for other levels.

New constraints differ from previous theoretical calculations.

Abstract

Resonances just above the proton threshold in 30S affect the 29P(p,gamma)30S reaction under astrophysical conditions. The (p,gamma)-reaction rate is currently determined indirectly and depends on the properties of the relevant resonances. We present here a method for finding the ratio between the proton and gamma partial widths of resonances in 30S. The widths are determined from the beta-2p and beta-p-gamma decay of 31Ar, which is produced at the ISOLDE facility at the European research organization CERN. Experimental limits on the ratio between the proton and gamma partial widths for astrophysical relevant levels in 30S have been found for the first time. A level at 4688(5) keV is identified in the gamma spectrum, and an upper limit on the proton to gamma width of 0.26 (95 % C.L.) is found. In the two-proton spectrum two levels at 5227(3) keV and 5847(4) keV are identified. These levels are previously seen to gamma decay and upper limits on the gamma to proton width of 0.5 and 9, respectively, (95 % C.L.) are found, where the latter differs from previous calculations.