Investigation of the thermonuclear18Ne(α,p)21Na reaction rate via resonant elastic scattering of

Abstract

The18 Ne(α,p) 21 Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus 22 Mg have been investigated by measuring the resonant elastic scattering of 21 Na+p. An 89 MeV 21 Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm 2 thick polyethylene (CH2)n target. The 21 Na beam intensity was about 2×10 5 pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of θc.m.≈175.2• , 152.2 • , and 150.5• by three sets of ∆E-E telescopes, respectively. The excitation function was obtained with the thick-target method over energies Ex( 22 Mg)=5.5-9.2 MeV. In total, 23 states above the proton-threshold in 22 Mg were observed, and their resonant parameters were determined via an R-matrix analysis of the excitation functions. We have made several new J π assignments and confirmed some tentative assignments made in previous work. The thermonuclear 18 Ne(α,p) 21 Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18 Ne(α,p) 21 Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, as well as the onset temperature of this breakout reaction in these astrophysical phenomena.

First measurement of S30+α resonant elastic scattering for the S30Kahl1, Yamaguchi2, Kubono3 et al. 2018Phys. Rev. CSelf Cite140100View full textAdd to dashboardCite

“…As relevant to the present study, Jordan et al importantly find smooth cross sections for 12 C and 16 O with 30 Si, the mirror nucleus of 30 S. Such behavior implies that a background source of α particles in the present work induced by CNO-group elements should have a relatively flat energy distribution. Figure 9(a) shows that our observed resonant structure is manifested as destructive interference with pure Rutherford scattering.…”

“…The 30 S RIB was produced inflight using the 3 He( 28 Si, 30 S)n transfer reaction. A 28 Si 9+ primary beam was extracted from an electron cycltron resonance ion source and accelerated to 7.3 MeV/u by the RIKEN AVF cyclotron (K ≈ 70) with a typical intensity of 80 pnA.…”

“…The pads are 3.5 mm in depth, surrounded by 0.25 mm of insulation on all sides (making 0.5 mm of insulation between each pad). Each pad is also 30 Top-down cartoon of the experimental setup and the detectors used in the data analysis (not to scale -PPACs in particular are much further from the active target chamber than depicted). The differences between a higher energy scattering (denoted 'α1') and a lower energy scattering ('α2') are shown.…”

“…As for the entrance window and quenching gas, the Coulomb barriers for 30 16 O, respectively. As for the incident 30 S beam energy impinging on the He+CO 2 gas, it is about 1.62 MeV/u, which yields E c.m.…”

“…9. 30 S+α elastic scattering excitation function including fits. (a) The energy range displayed is the entire set of continuous data in the raw excitation function, except at the lower energy side where the plot is terminated at the point where all the α particles can no longer reach the detector from stopping in the fill gas.…”