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The Mg–Al cycle is characteristic of the high-temperature (T ∼ 0.055 GK) H-burning of evolved stars and their nucleosynthesis. A proper comprehension of this reaction network can help in solving debated questions such as the occurrence of anticorrelation in Mg–Al abundances in globular clusters. Recent high-resolution surveys have shown that such an anticorrelation may hide the existence of multiple stellar populations and that the relative abundances of Mg isotopes may not be correlated with Al. Proton-induced reactions on 27Al play a key role in this respect, in particular the interplay between the (p, α) and (p, γ) channels, determining the closure (or not) of the Mg–Al cycle. Presently, the situation is still debated owing to the large uncertainty affecting existing experimental nuclear data. A recent indirect measurement indicates a further reduction in the 27Al(p, α)24Mg reaction rate with respect to the ones commonly adopted in astrophysical models. In the present work, we update the 27Al(p,γ)28Si reaction rate based on the same indirect measurement results. In the case of AGB stars experiencing hot bottom burning, the revised rate would lead to a ∼35% increase in 27Al abundance with respect to what is presently foreseen, with interesting astrophysical consequences.

Nuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path that drove the elemental nucleosynthesis in the first 20 min of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a difficult task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the primordial nucleosynthesis network. In this work we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the 3 He (n,p) 3 H reaction after a detailed study of the 2 H ( 3 He ,pt)H three-body process. Data extracted from the present measurement are compared with other published sets.

The thermal neutron capture cross-section of cerium isotopes 140 Ce and 142 Ce, were measured with detailed covariance analysis using naturally occurring cerium oxide samples. We conducted irradiation with an Am–Be neutron source at the Manipal Institute of Technology and performed offline gamma-ray measurements via High Purity Germanium (HPGe) Detector. The neutron spectrum from the irradiation location was obtained by employing multiple foil activation techniques and spectrum unfolding methods. The present results provide precise thermal neutron capture cross-section data with detailed covariance analysis. The measured cross sections, 0.54 ± 0.03 barns for 140 Ce and 0.83 ± 0.04 barns for cerium-142, are compared with previous measurements and with the latest available evaluated nuclear libraries. It is observed that the presently measured thermal cross-section values of 140 Ce and 142 Ce are lower than the evaluated data but have higher accuracy compared to the previous measurements with larger uncertainties. Further, the measured thermal neutron capture cross-section values of 140 Ce and 142 Ce isotopes are in good agreement with the previous measurements than the evaluations. Thus, the current state of nuclear data evaluation requires improvement for cerium isotopes.

The abundance of 26Al carries a special role in astrophysics, since it probes active nucleosynthesis in the Milky Way and constrains the Galactic core-collapse supernovae rate. It is estimated through the detection of the 1809 keV γ-line and from the superabundance of 26Mg in comparison with the most abundant Mg isotope (A = 24) in meteorites. For this reason, high precision is necessary also in the investigation of the stable 27Al and 24Mg isotopes. Moreover, these nuclei enter the so-called MgAl cycle, playing an important role in the production of Al and Mg. Recently, high-resolution stellar surveys have shown that the Mg–Al anticorrelation in red-giant stars in globular clusters may hide the existence of multiple stellar populations, and that the relative abundances of Mg isotopes may not be correlated with Al. The common thread running through these astrophysical scenarios is the 27Al(p,α)24Mg reaction, which is the main 27Al destruction channel and directly correlates its abundance with the 24Mg one. Since available reaction rates show large uncertainties owing to the vanishingly small cross section at astrophysical energies, we have applied the Trojan Horse Method to deduce the reaction rate with no need of extrapolation. The indirect measurement made it possible to assess the contribution of the 84 keV resonance and to lower upper limits on the strength of nearby resonances. In intermediate-mass AGB stars experiencing hot bottom burning, a sizeable increase in surface aluminum abundance is observed at the lowest masses, while 24Mg is essentially unaffected by the change in the reaction rate.

12C +12 C is the main reaction during core and shell carbon burning in massive stars, however, at temperatures higher than 109K when most of the carbon is depleted and its abundance is lower than 16O, the 12C +16 O fusion can also become relevant. Moreover, 12C +16 O reaction can ignite also in the scenario of explosive carbon burning. The astrophysical energy region of interest thus ranges from 3 to 7.2 MeV in the center-of-mass frame. There are various measurements of the cross-section available in the literature, however, they all stop around 4 MeV, making extrapolation necessary at lower energies. To try to solve this uncertainty and corroborate direct measurement the Trojan Horse Method was applied to three-body processes 16O(14N, α24Mg)2H and 16O(14N, p27Al)2H to study the 16O(12C, α)24Mg and 16O(12C, p)27Al reactions.

The 100Mo(γ, n) reaction cross-section was experimentally determined at end point bremsstrahlung energy of 10 and 12.5 MeV using off-line γ-ray spectrometric technique. It was also found that 100Mo(γ, n) reaction cross-section increases sharply from the end point bremsstrahlung energy of 10 MeV to 12.5 MeV, which may be because of GDR around the energy region of 12–16 MeV. The 100Mo(γ, n) reaction cross-section as a function of photon energy was calculated theoretically using TALYS 1.2 computer code. The flux-weighted average values of 100Mo(γ, n) reaction cross-section for bremsstrahlung having end point energy of 10 and 12.5 MeV were also calculated using the experimental and theoretical data of mono-energetic photon. The present experimental 100Mo(γ, n) reaction cross-sections were compared with the bremsstrahlung flux-weighted average values of experimental and theoretical data and found to be in the lower side for 10 MeV and in the higher side for 12.5 MeV.

The 56Fe(n, p)56Mn reaction cross-section at neutron energies of 5.9 ± 0.6, 9.85 ± 0.38, 14.8 ± 0.1 and 15.5 ± 0.7 MeV from the 7Li(p, n) as well as 3H(d, n) reactions has been experimentally measured using activation and off-line γ-ray spectrometric technique. The experimentally determined 56Fe(n, p)56Mn reaction cross-sections from the present work were compared with the latest available evaluated nuclear data libraries of ENDF/B-VII.1, JENDL-4.0 and JEFF-3.1/A. The present data along with the literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels. The measured cross-sections were also estimated theoretically using TALYS-1.4 and EMPIRE-2.19 computer codes over neutron energies from near threshold to 20 MeV to compare with the experimental data.

The reaction cross-sections for 64Ni(n, γ) 65Ni at En = 0.025 eV and 58Ni (n, p) 58Co at En = 3.7 MeV have been experimentally determined using activation and off-line γ-ray spectrometric technique. The thermal neutron flux used is from the thermal Column of the reactor APSARA at BARC, Mumbai, whereas the neutron energy of 3.7 MeV is from the 7Li(p, n) reaction at Pelletron facility, TIFR, Mumbai. The 64Ni(n, γ) 65Ni and 58Ni(n, p) 58Co reactions cross-sections from present work are compared with the available literature data and found to be in good agreement. The 58Ni(n, p) 58Co reaction as a function of neutron energy is also calculated theoretically using TALYS computer code version 1.2 and found to be higher than the experimental data.

The 238U(n, γ)239U reaction cross-section at average neutron energy of 3.7 ± 0.3 MeV from the 7Li(p, n)7Be reaction has been determined using activation and off-line γ-ray spectrometric technique. The 238U(n, γ)239U and 238U(n, 2n)237U reaction cross-sections at average neutron energy of 9.85 ± 0.38 MeV from the same 7Li(p, n)7Be reaction have been also determined using the above technique. The experimentally determined 238U(n, γ)239U and 238U(n, 2n)237U reaction cross-sections were compared with the evaluated data of ENDF/B-VII, JENDL-4.0, JEFF-3.1 and CENDL-3.1. The experimental values were found to be in general agreement with the evaluated value based on ENDF/B-VII, and JENDL-4.0 but not with the JEFF-3.1 and CENDL-3.1. The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels including fission. The 238U(n, γ)239U and 238U(n, 2n)237U reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were also found to be in agreement experimental data.