Theoretical studies of proton capture reactions in A ∼ 25 proton-rich nuclei

Abstract

The direct proton capture and resonance proton capture properties of stellar reactions 22 Mg(p,γ) 23 Al and 26 Si(p,γ) 27 P are studied by employing a mean-field potential obtained from the Skyrme-HartreeFock (SHF) model. Calculations with the SHF potential reproduce well the loosely-bound structure of the ground states as well as the widths of the resonant states in these nuclei. With the obtained potential we estimate the reaction rates of direct proton capture and resonance proton capture to nuclei 23 Al and 27 P. The effect of the 27 P loosely-bound structure on the S factor of the direct proton capture is also discussed.proton capture reaction, mean field potential, proton-rich nuclei, shell model Proton capture reaction is of increasing interest in nuclear physics as well as in astrophysics. The famous Carbon-Nitrogen-Oxygen cycle starts from the proton capture of 12 C. The nucleosynthesis of proton-rich heavy nuclides (that are usually called p-nuclei) proceeds mostly through the proton capture and/or photo nuclear reactions. P -nuclei with the mass number up to A ∼ 100 can also be produced by the rapid proton capture process (rpprocess) [1,2] . The rp-process is a sequence of (p, γ) reactions and β + decays that are responsible for the burning of hydrogen into heavier elements [3] . The hydrogen burning rate is strongly influenced by the proton capture reaction [4] . It has also been shown that the proton capture reaction is helpful for the investigation of nuclear spectroscopy and the production of proton-rich exotic nuclei [5] . Therefore it is very useful to investigate the dynamical processes involving the proton capture.Of special interest is the proton capture to exotic nuclei with loosely-bound s 1/2 proton. The recent experiment of the 16 O(p, γ) 17 F stellar reaction shows that the halo structure of the π1s 1/2 orbit in 17 F can significantly enhance the astrophysical S factor of the direct proton capture to the nucleus at low bombing energies [6] . In the nuclear chart, the nuclei, 17 F, 23 Al and 26,27,28 P, are among the lightest ones which may carry looselybound 1s 1/2 protons in the ground or low-lying states [6−22] . It remains unclear whether the looselybound structure of the Al and P isotopes affects the direct capture reaction property. Moreover, the 22 Mg(p, γ) 23 Al and 26 Si(p, γ) 27 P reactions are important for the understanding of the nucleosyn-

β -decay spectroscopy of S27

“…The high and low values of the nonresonant reaction rate were calculated from the largest and smallest known zero-energy S factors, respectively. 27 Mg ANC 87(11) Timofeyuk [117] microscopic cluster model 50(13) Iliadis [116] compilation 54.5 Togano [37] Coulomb dissociation of 27 P 2 1 Marganiec [39] Coulomb dissociation of 27 [32], Guo et al [34], Qi et al [118], Iliadis et al [116], Togano et al [37], and Marganiec et al [39], respectively, to that determined in the present work. The uncertainty band is from the present work.…”

“…The total width was calculated to 5.98(186) meV using the relation tot = p + γ , so the lifetime was calculated to be 110 (35) fs using the relation τ =h/ tot . The information about the key 3/2 + resonance needed to determine the reaction rate is summarized and compared to literature values [18,32,[34][35][36][37][38][39]89,93,94,[116][117][118][119] in Table VIII. The high and low values of the resonant reaction rate were derived from a one standard deviation variation of the resonance parameters.…”

“…Recently, Marganiec et al reported a new ωγ of 0.3504 meV and E r of 722(56) keV for the 5/2 + resonance with a similar approach [39]. Prior to these two measurements, a calculated ωγ of 0.99 meV [93] had been widely adopted [32,34,118]. Such a tiny γ value is expected to be far beyond the threshold of the sensitivity of the present experiment, nevertheless, the E r of the 5/2 + resonance was measured to be 762(8) keV directly in our work, and an average ωγ value of 0.65 +0.34 −0.30 was estimated by considering all the available previously determined ωγ values.…”

Configuration-constrained total-Routhian-surface models

“…PNC 模型具有基于核子 -核子 (NN) 相互作用 的传统壳模型 [138,139] 的架构, 但是 PNC 的模型空 间比基于真实 NN 相互作用壳模型计算的模型空间 要小得多. 这是因为 PNC 中只包含了剩余对相互作 用以及采用了 CMPC 截断, 这样可以有效包含所有 重要组态且明显减小模型空间.…”

Recent progress in theoretical nuclear physics related to large-scale scientific facilities

“…The direct proton capture and resonance proton capture properties of stellar reactions 22 Mg(p,γ) 23 Al and 26 Si(p,γ) 27 P are studied by employing a mean-field potential obtained from the Skyrme-Hartree-Fock (SHF) model [37]. Calculations with the SHF potential reproduce well the looselybound structure of the ground states as well as the widths of the resonant states in these nuclei.…”