First measurement of S30+α resonant elastic scattering for the S30(α,p) reaction rate Academic Article uri icon

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  • Background: Type I x-ray bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of an accreting neutron star. The $^{30}$S($\alpha$,p) reaction plays a critical role in burst models, yet insufficient experimental information is available to calculate a reliable, precise rate for this reaction. Purpose: Our measurement was conducted to search for states in $^{34}$Ar and determine their quantum properties. In particular, natural-parity states with large $\alpha$-decay partial widths should dominate the stellar reaction rate. Method: We performed the first measurement of $^{30}$S+$\alpha$ resonant elastic scattering up to a center-of-mass energy of 5.5 MeV using a radioactive ion beam. The experiment utilized a thick gaseous active target system and silicon detector array in inverse kinematics. Results: We obtained an excitation function for $^{30}$S($\alpha$,$\alpha$) near $150^{\circ}$ in the center-of-mass frame. The experimental data were analyzed with an $R$-Matrix calculation, and we observed three new resonant patterns between 11.1 and 12.1 MeV, extracting their properties of resonance energy, widths, spin, and parity. Conclusions: We calculated the resonant thermonuclear reaction rate of $^{30}$S($\alpha$,p) based on all available experimental data of $^{34}$Ar and found an upper limit about one order of magnitude larger than a rate determined using a statistical model. The astrophysical impact of these two rates has been investigated through one-zone postprocessing type I x-ray burst calculations. We find that our new upper limit for the $^{30}$S($\alpha$,p)$^{33}$Cl rate significantly affects the predicted nuclear energy generation rate during the burst.


  • Kahl, D
  • Yamaguchi, H
  • Kubono, S
  • Chen, Alan
  • Parikh, A
  • Binh, DN
  • Chen, J
  • Cherubini, S
  • Duy, NN
  • Hashimoto, T
  • Hayakawa, S
  • Iwasa, N
  • Jung, HS
  • Kato, S
  • Kwon, YK
  • Nishimura, S
  • Ota, S
  • Setoodehnia, K
  • Teranishi, T
  • Tokieda, H
  • Yamada, T
  • Yun, CC
  • Zhang, LY

publication date

  • January 3, 2018