اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدالعامل S الفلكي للالتقاط الإشعاعي 12N(p،gamma)13O الذي تم تحديده من تفاعل النقل الإشعاعي للبروتون 14N(12N،13O)13C
Astrophysical S factor for the radiative capture 12N(p,gamma)13O determined from the 14N(12N,13O)13C proton transfer reaction
654
0
0.0
(
0
)
اسأل ChatGPT حول البحث
تم التحقق من تقطع الصليب لإطلاق الذرات الشعاعية للاستيلاء على النوكليوس 12N على الخط الشريط باستخدام طريقة المعامل التقليدي الأشعاعي (ANC). استخدمنا تفاعل النقل البروتوني 14N (12N, 13O) 13C عند 12 ميجا فولت في النوكلون لاستخراج ANC لـ 13O -> 12N + p وحساب من ذلك العنصر الفلكي S لإطلاق الذرات الشعاعية للاستيلاء على 12N (p, gamma) 13O. تم مناقشة الحسابات البحثية البصرية المستخدمة وتحليل DWBA لتفاعل النقل البروتوني. للقناة الدخولية، تم تحديد الحساب البحثي البصري من التصدير المرن الذي تم إجراؤه في نفس الوقت مع القياس النقل. من النقل، تم تحديد مربع ANC، C ^ 2 (13Og.s.) = 2.53 +/- 0.30 fm-1، ومن ثم تم الحصول على قيمة 0.33 (4) كيلو فولت برم بالنسبة لعنصر الفلكي S المباشر في الصفر الطاقة. التداخل البنائي في الأطوال المنخفضة بين الاستيلاء المباشر والاستيلاء الحالي يؤدي إلى تعزيز Stotal (0) = 0.42 (5) كيلو فولت برم. تم التحقق من إطلاق الذرات الشعاعية للاستيلاء على 12N (p, gamma) 13O بشأن تطور نجوم الأكثر ثروة في الهيدروجين من الأجيال الثالثة، لدور قد يلعبه في عمليات حرق الذرات الشعاعية النووية السريعة المحتملة في هذه الكائنات.
The cross section of the radiative proton capture reaction on the drip line nucleus 12N was investigated using the Asymptotic Normalization Coefficient (ANC) method. We have used the 14N(12N,13O)13C proton transfer reaction at 12 MeV/nucleon to extract the ANC for 13O -> 12N + p and calculate from it the direct component of the astrophysical S factor of the 12N(p,gamma)13O reaction. The optical potentials used and the DWBA analysis of the proton transfer reaction are discussed. For the entrance channel, the optical potential was inferred from an elastic scattering measurement carried out at the same time with the transfer measurement. From the transfer, we determined the square of the ANC, C^2(13Og.s.) = 2.53 +/- 0.30 fm-1, and hence a value of 0.33(4) keVb was obtained for the direct astrophysical S factor at zero energy. Constructive interference at low energies between the direct and resonant captures leads to an enhancement of Stotal(0) = 0.42(5) keVb. The 12N(p,gamma)13O reaction was investigated in relation to the evolution of hydrogen-rich massive Population III stars, for the role that it may play in the hot pp-chain nuclear burning processes, possibly occurring in such objects.
قيم البحث
اقرأ أيضاً
The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The $^{12}$N($p$,,$gamma$)$^{13}$O reaction is an important branching point in the rap-processes, which are believed to be
alternative paths to the slow 3$alpha$ process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angular distribution of the $^2$H($^{12}$N,,$^{13}$O)$n$ proton transfer reaction at $E_{mathrm{c.m.}}$ = 8.4 MeV has been measured for the first time. Based on the Johnson-Soper approach, the square of the asymptotic normalization coefficient (ANC) for the virtual decay of $^{13}$O$_mathrm{g.s.}$ $rightarrow$ $^{12}$N + $p$ was extracted to be 3.92 $pm$ 1.47 fm$^{-1}$ from the measured angular distribution and utilized to compute the direct component in the $^{12}$N($p$,,$gamma$)$^{13}$O reaction. The direct astrophysical S-factor at zero energy was then found to be 0.39 $pm$ 0.15 keV b. By considering the direct capture into the ground state of $^{13}$O, the resonant capture via the first excited state of $^{13}$O and their interference, we determined the total astrophysical S-factors and rates of the $^{12}$N($p$,,$gamma$)$^{13}$O reaction. The new rate is two orders of magnitude slower than that from the REACLIB compilation. Our reaction network calculations with the present rate imply that $^{12}$N($p,,gamma$)$^{13}$O will only compete successfully with the $beta^+$ decay of $^{12}$N at higher ($sim$two orders of magnitude) densities than initially predicted.
The astrophysical S-factor of 14N(p,gamma)15O has been measured for effective center-of-mass energies between E_eff = 119 and 367 keV at the LUNA facility using TiN solid targets and Ge detectors. The data are in good agreement with previous and rece
nt work at overlapping energies. R-matrix analysis reveals that due to the complex level structure of 15O the extrapolated S(0) value is model dependent and calls for additional experimental efforts to reduce the present uncertainty in S(0) to a level of a few percent as required by astrophysical calculations.
The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, 14N(p,gamma)15O, which proceeds by capture to the ground and several excited states in 15O. Previous extrapolations for the ground state contrib
ution disagreed by a factor 2, corresponding to 15% uncertainty in the total astrophysical S-factor. At the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy, a new experiment on ground state capture has been carried out at 317.8, 334.4, and 353.3 keV center-of-mass energy. Systematic corrections have been reduced considerably with respect to previous studies by using a Clover detector and by adopting a relative analysis. The previous discrepancy has been resolved, and ground state capture no longer dominates the uncertainty of the total S-factor.
The 14N(p,gamma)15O reaction plays a vital role in various astrophysical scenarios. Its reaction rate must be accurately known in the present era of high precision astrophysics. The cross section of the reaction is often measured relative to a low en
ergy resonance, the strength of which must therefore be determined precisely. The activation method, based on the measurement of 15O decay, has not been used in modern measurements of the 14N(p,gamma)15O reaction. The aim of the present work is to provide strength data for two resonances in the 14N(p,gamma)15O reaction using the activation method. The obtained values are largely independent from previous data measured by in-beam gamma-spectroscopy and are free from some of their systematic uncertainties. Solid state TiN targets were irradiated with a proton beam provided by the Tandetron accelerator of Atomki using a cyclic activation. The decay of the produced 15O isotopes was measured by detecting the 511 keV positron annihilation gamma-rays. The strength of the Ep = 278 keV resonance was measured to be 13.4 +- 0.8 meV while for the Ep = 1058 keV resonance the strength is 442 +- 27 meV. The obtained Ep = 278 keV resonance strength is in fair agreement with the values recommended by two recent works. On the other hand, the Ep = 1058 keV resonance strength is about 20% higher than the previous value. The discrepancy may be caused in part by a previously neglected finite target thickness correction. As only the low energy resonance is used as a normalization point for cross section measurements, the calculated astrophysical reaction rate of the 14N(p,gamma)15O reaction and therefore the astrophysical consequences are not changed by the present results.
The $^{13}C(^{14}N,^{13}C)^{14}N$ proton exchange reaction has been measured at an incident energy of 162 MeV. Angular distributions were obtained for proton transfer to the ground and low lying excited states in $^{14}N$. Elastic scattering of $^{14
}N$ on $^{13}C$ also was measured out to the rainbow angle region in order to find reliable optical model potentials. Asymptotic normalization coefficients for the system $^{13}C+pto {}^{14}N$ have been found for the ground state and the excited states at 2.313, 3.948, 5.106 and 5.834 MeV in $^{14}N$. These asymptotic normalization coefficients will be used in a determination of the S-factor for $^{7}Be(p,gamma)^{8}B$ at solar energies from a measurement of the proton transfer reaction $^{14}N(^{7}Be,^{8}B)^{13}C$.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
