α -unbound levels in Ar34 from Ar36(p,

Abstract

The 30 S(α,p) 33 Cl reaction has been identified in several Type-1 X-ray Bursts (XRB) sensitivity studies as a significant reaction within the αp-process, possibly influencing not only the abundances of burst ashes but also the bolometric shape of double-peaked light curves coming from certain XRB systems. Given the dearth of experimental data on the 30 S(α,p) 33 Cl reaction at burst temperatures, we have performed high energy-resolution forward-angle 36 Ar(p,t) 34 Ar measurements in order to identify levels in 34 Ar that could appear as resonances in the 30 S(α,p) 33 Cl reaction. Energies of levels identified in this work, along with model-based assumptions for spin assingments and spectroscopic factors, were then used to determine a rate for the 30 S(α,p) 33 Cl reaction based on a narrow-resonance formalism. The rates determined in this work are then compared with two standard Hauser-Feshbach model prediction over a range of XRB temperatures.

Search for Nova Presolar Grains: γ -Ray Spectroscopy of Ar34 and its Relevance for the Astrophysical Kennington1, Lotay2, Doherty3 et al. 2020Phys. Rev. Lett.

“…In general, good agreement is found between the presently determined 34 Ar excitation energies, and Refs. [15,16]. Moreover, previously observed γ decays at 2091.3(5), 1197.5(4), 3289.1(10), 1785.6(7), 1228.4(5), and 2424.7 (22) keV from the well-known 2 þ 1 , 2 þ 2 , 0 þ 2 and 3 − 1 levels in 34 Ar [16] are also observed here.…”

“…A γ-γ coincidence matrix was produced and analyzed, together with γ-ray singles data, in order to obtain information on the 34 Ar and 34 S decay schemes. Table I presents the level energies, transition energies, γray intensities, and spin-parity assignments for observed excited states in 34 Ar, together with a comparison to previous work [15,16]. In general, good agreement is found between the presently determined 34 Ar excitation energies, and Refs.…”

“…In that study [15], 16 excited levels were observed, but no spinparity information was obtained. Moreover, the 36 Arðp; tÞ reaction selectively populates natural-parity states and, as such, it is likely that there are a number of excited states in 34 Ar corresponding to key resonances in the 33 Clðp; γÞ reaction that have yet to be identified [15]. In this Letter, we describe a measurement that employs a heavy-ion fusionevaporation reaction to simultaneously populate excited states in the astrophysically important nucleus 34 Ar and its well-studied mirror analog, 34 S [16].…”

“…Consequently, the 33 Clðp; γÞ 34 Ar reaction is currently uncertain by orders of magnitude over the temperature range of classical novae, leading to variations in the predicted ejected abundances of 33 S and 34 S by factors of ∼18 and ∼3, respectively [12]. Recently, a high-resolution 36 Arðp; tÞ reaction study to identify excited states in 34 Ar was performed by Long et al [15]. In that study [15], 16 excited levels were observed, but no spinparity information was obtained.…”

“…Recently, a high-resolution 36 Arðp; tÞ reaction study to identify excited states in 34 Ar was performed by Long et al [15]. In that study [15], 16 excited levels were observed, but no spinparity information was obtained. Moreover, the 36 Arðp; tÞ reaction selectively populates natural-parity states and, as such, it is likely that there are a number of excited states in 34 Ar corresponding to key resonances in the 33 Clðp; γÞ reaction that have yet to be identified [15].…”