Structure effects in theN15(n,γ)N16radiative capture reaction from the Coulomb dissocia

Abstract

Background:The 15 N(n, γ) 16 N reaction plays an important role in red giant stars and also in inhomogeneous big bang nucleosynthesis. However, there are controversies regarding spectroscopic factors of the four low-lying states of 16 N, which have direct bearing on the total direct capture cross section and also on the reaction rate. Direct measurements of the capture cross section at low energies are scarce and is available only at three energies below 500 keV.Purpose: The aim of this paper is to calculate the 15 N(n, γ) 16 N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of 16 N to the cross section.Method: A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of 16 N on Pb at 100 MeV/u. This is then related to the photodisintegration cross section of 16 N(γ, n) 15 N and subsequently invoking the principle of detailed balance, the 15 N(n, γ) 16 N capture cross section is calculated. Results:The non-resonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seems to favor a more single particle nature for the low-lying states of 16 N. The total neutron capture rate is also calculated by summing up non-resonant and resonant (significant only at temperatures greater than 1 GK) contributions and comparison is made with other charged particle capture rates. In the typical temperature range of 0.1 − 1.2 GK, almost all the contribution to the reaction rate comes from capture cross sections below 0.25 MeV. Conclusion:We have attempted to resolve the discrepancy in the spectroscopic factors of low-lying 16 N levels and conclude that it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture cross section for the reaction, especially below 0.25 MeV.

Determination of the Mg36(n,γ)Mg37 reaction rate from Coulomb dissociation of Shubhchintak1, Chatterjee2, Shyam3 2017Phys. Rev. CSelf Cite

“…[ 13,22,[26][27][28][29]]. Nevertheless, in the context of the reaction studied in this paper, we have checked that the breakup cross sections are indeed dominated by the E1 multipolarity by evaluating the Coulomb dissociation cross sections within the first order Coulomb excitation theory [25].…”

Status of nuclear physics behind nucleosynthesis processes: The role of exotic neutron-rich nuclei

“…To address this anomaly, (Neelam et al 2015) recalculated the rates by considering the Coulomb dissociation of 16 N, and showed that they agree with the measurements of Bardayan et al (2008) and (Meissner et al 1996). This gave credence to the interpretation that the first four levels in 16 N could have a single-particle character.…”

Structural effects of Na34 in the Na33(n,γ)NaSingh1, Shubhchintak2, Chatterjee3 2017Phys. Rev. CSelf Cite9060View full textAdd to dashboardCite

“…Ideally, one would desire the experimentally measured dipole response or the relative energy spectra results to have a good understanding on the continuum structure of 34 Na, not much about which is known. We have assumed it to be non-resonant for our calculations, but even for a continuum with narrow resonances, reaction rates can be computed easily, albeit with a different formalism [42]. Experimental information about the total cross-section for the CD of 34 Na and the momentum distributions of the charged core is also prudently sought to restrict the g.s.…”

“…We have then used the principle of detailed balance to study the reverse capture reaction 33 Na(n,γ) 34 Na and calculate its cross-section and reaction rate at the stellar temperature range concerned. This indirect technique had been used in the past to study various capture reactions and their rates [29,42,52].…”

“…Hence, knowing the relative energy spectrum of a single multipole dominated reaction from CD studies, and using Eqs. (4), (5) and (6), we can easily calculate reaction rates of stellar reactions in this elegant indirect manner [29,42]. Such indirect approaches are used quite extensively in nuclear astrophysics for studying a diversity of nuclear reactions and obtaining information about the events occurring in the stellar plasma [43][44][45].…”