Background: 34 Na is conjectured to play an important role in the production of seed nuclei in the alternate r -process paths involving light neutron rich nuclei very near the β-stability line, and as such, it is important to know its ground state properties and structure to calculate rates of the reactions it might be involved in, in the stellar plasma. Found in the region of 'island of inversion', its ground state might not be in agreement with normal shell model predictions.Purpose: The aim of this paper is to study the elastic Coulomb breakup of 34 Na on 208 Pb to give us a core of 33 Na with a neutron and in the process we try and investigate the one neutron separation energy and the ground state configuration of 34 Na.Method: A fully quantum mechanical Coulomb breakup theory within the architecture of post-form finite range distorted wave Born approximation extended to include the effects of deformation is used to research the elastic Coulomb breakup of 34 Na on 208 Pb at 100 MeV/u. The triple differential cross-section calculated for the breakup is integrated over the desired components to find the total cross-section, momentum and angular distributions as well as the average momenta, along with the energy-angular distributions.Results: The total one neutron removal cross-section is calculated to test the possible ground state configurations of 34 Na. The average momentum results along with energy-angular calculations indicate 34 Na to have a halo structure. The parallel momentum distributions with narrow full widths at half maxima signify the same. Conclusion:We have attempted to analyse the possible ground state configurations of 34 Na and in congruity with the patterns in the 'island of inversion' conclude that even without deformation, 34 Na should be a neutron halo with a predominant contribution to its ground state most probably coming from 33 Na(3/2 + ) ⊗ 2p 3/2 ν configuration. We also surmise that it would certainly be useful and rewarding to test our predictions with an experiment to put stricter limits on its ground state configuration and binding energy. * gagandph@iitr.ac.in

We calculate Coulomb breakup of the neutron rich nucleus 37 Mg on a Pb target at the beam energy of 244 MeV/nucleon within the framework of a finite range distorted wave Born approximation theory that is extended to include the effects of projectile deformation. In this theory, the breakup amplitude involves the full wave function of the projectile ground state. Calculations have been carried out for the total one-neutron removal cross section (σ −1n ), the neutron-core relative energy spectrum, the parallel momentum distribution of the core fragment, the valence neutron angular, and energy-angular distributions. The calculated σ −1n has been compared with the recently measured data to put constraints on the spin parity, and the one-neutron separation energy (S n ) of the 37 Mg ground state ( 37 Mg gs ). The dependence of σ −1n on the deformation of this state has also been investigated. While a spin parity assignment of 7/2 − for the 37 Mg gs is ruled out by our study, neither of the 3/2 − and 1/2 + assignments can be clearly excluded. Using the spectroscopic factor of one for both the 3/2 − and 1/2 + configurations and ignoring the projectile deformation effects, the S n valuesEmail addresses: shub1dph@iitr.ac.in (Shubhchintak), nph10dph@iitr.ac.in (Neelam), rcfphfph@iitr.ac.in (R. Chatterjee), radhey.shyam@saha.ac.in (R. Shyam), kazuo.tsushima@gmail.com (K. Tsushima) Preprint submitted to ElsevierMarch 25, 2015 of 0.35±0.06 MeV and 0.50±0.07 MeV, respectively, are extracted for the two configurations. However, the extracted S n is strongly dependent on the spectroscopic factor and the deformation effects of the respective configuration. The narrow parallel momentum distribution of the core fragment and the strong forward peaking of the valence neutron angular distribution suggest a one-neutron halo configuration in either of the 2p 3/2 and 2s 1/2 configurations of the 37 Mg ground state.

We present a fully quantum mechanical theory to study the effects of deformation on various reaction observables in the Coulomb breakup of neutron rich exotic medium mass nuclei on heavy targets within the framework of finite range distorted wave Born approximation by using a deformed Woods-Saxon potential. As an application of this theory, we calculate the one-neutron removal cross section, relative energy spectra, parallel momentum distributions and angular distributions in the breakup of 31 Ne on Pb and Au targets at 234 MeV/u. We suggest ways to put constraints on the large uncertainty in the one-neutron separation energy of 31 Ne and also argue that if 31 Ne is indeed a halo nucleus then it should be a deformed one.

During the Big Bang, 6 Li was synthesized via the 2 H(α, γ) 6 Li reaction. After almost 25 years of the failed attempts to measure the 2 H(α, γ) 6 Li reaction in the lab at the Big Bang energies, just recently the LUNA collaboration presented the first successful measurements at two different Big Bang energies [M. Anders et al., Phys. Rev. Lett. 113, 042501 (2014)]. In this paper we will discuss how to improve the accuracy of the direct experiment. To this end the photon's angular distribution is calculated in the potential model. It contains contributions from electric dipole and quadrupole transitions and their interference, which dramatically changes the photon's angular distribution. The calculated distributions at different Big Bang energies have a single peak at ∼ 50 • .These calculations provide the best kinematic conditions to measure the 2 H(α, γ) 6 Li reaction. The expressions for the total cross section and astrophysical factor are also derived by integrating the differential cross section over the photon's solid angle. The LUNA data are in excellent agreement with our calculations using a potential approach combined with a well established asymptotic normalization coefficient for 6 Li → α + d. Comparisons of the available experimental data for the S 24 astrophysical factor and different calculations are presented. The Big Bang lithium isotopic ratio 6 Li/ 7 Li = (1.5 ± 0.3) × 10 −5 following from the LUNA data and the present analysis are discussed in the context of the disagreement between the observational data and the standard Big Bang model, which constitutes the second Lithium problem.

We apply the R-matrix method in Distorted Wave Born Approximation (DWBA) calculations. The internal wave functions are expanded over a Lagrange mesh, which provides an efficient and fast technique to compute matrix elements. We first present an outline of the theory, by emphasizing the R-matrix aspects. The model is applied to the 16 O(d, p) 17 O and 12 C( 7 Li, t) 16 O reactions, typical of nucleon and of α transfer, respectively. We illustrate the sensitivity of the cross sections with respect to the R-matrix parameters, and show that an excellent convergence can be achieved with relatively small bases. We also discuss the effects of the remnant term in DWBA calculations, and address the question of the peripherality in transfer reactions. We suggest that uncertainties on spectroscopic factors could be underestimated in the literature.

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.

We propose the use of neutron poisons in reactions induced by radioactive beams as a test of theoretical models aiming to relate neutron capture in nuclei with neutron surrogate reactions such as (d,p) reactions. We exploit the approximations necessary to obtain a direct relation between the two reactions; surrogate vs. neutron capture. We also show how this is intimately related to the momentum distribution of the neutron within the deuteron. The models we use are based on the theory of inclusive breakup reactions commonly employed in the treatment of incomplete fusion and surrogate method. Such theories were developed in the 80's by Ichimura, Autern and Vincent [Phys. Rev. C 32, 431 (1985)], Udagawa and Tamura [Phys. Rev. C 24, 1348Rev. C 24, (1981] and Hussein and McVoy [Nucl. Phys. A 445, 124 (1985)]. We use these theories to derive an expression for the proton yield in the reaction A(d,p)B. The capture reaction n + A → B is then extracted using reasonable approximations. By recalling an old method proposed by Serber [Phys. Rev. 80, 1098 Nature 166, 709 (1950)] we explain how the momentum distribution of neutrons within the deuteron will depend on the short-range dependence of the nucleon-nucleon force. The relevance of our work to nucleosynthesis in the rapid neutron capture process is emphasized.

No abstract