The elastic scattering angular distributions of the tightly bound 11B on the 89Y target, at bombarding energies in the vicinity of the Coulomb barrier have been measured. The energy dependence of the interaction potential was analyzed using the Woods-Saxon potential (WSP) and São Paulo potential (SPP). Both models confirmed the presence of the typical threshold anomaly. To account for varying sizes and Coulomb barriers, the total reaction cross sections for the current and similar mass-range systems were gathered from literature and reduced. This normalization allows for a direct comparison by eliminating trivial effects arising due to different sizes and different Coulomb barriers. To quantify how direct reaction channels affect the total reaction cross section, one-channel calculations, that account only for fusion, were performed for all systems. These calculations isolate the fusion process to highlight the specific impact of the direct channels. By applying the reduction procedure, it is concluded that there is absence of the breakup channel but other possible channels like inelastic, transfer etc. are present.

The reaction rates of 22Ne(alpha, n)25Mg and its competing channel 22Ne(alpha, gamma)26Mg control the production of neutron flux for weak s-process nucleosynthesis in low mass asymptotic giant branch stars and in massive stars with M >= 10M circle dot. The temperature range of interest for these reactions lies between 0.2 and 0.4 GK. However, the rates of these reactions are poorly constrained at these temperatures due to uncertainties in the nuclear properties of several resonance states in the compound nucleus 26Mg, lying within the Gamow window. The present work reports a full R-matrix evaluation of the 22Ne(alpha, n)25Mg and 22Ne(alpha, gamma)26Mg reaction rates using updated nuclear data of 26Mg states. Previous rate evaluation by Adsley et al and R-matrix calculations of Wiescher et al were limited by using narrow resonance approximations and omission of the resonances below Er = 705 keV, respectively. In this work, the R-matrix fit to the available 22Ne(alpha, n)25Mg reaction data is performed by including the contributions of previously neglected resonances below Er = 705 keV and considering the interference effects. The (alpha, n) reaction rate from the present R-matrix evaluations is noticeably higher than the narrow resonance approximation calculations in the temperature range 0.1-0.3 GK. In particular, the present (alpha, n) reaction rate is significantly higher (7.5 - 4.5 times) compared to Adsley et al at 0.2-0.3 GK and approximate to 2 times greater than Wiescher et al at 0.3 GK. The estimated reaction rate ratio of (alpha, n) to (alpha, gamma) in the relevant temperature window 0.2-0.8 GK indicates that the production of neutrons for the s-process is more likely than the radiative alpha capture reaction, compared to the previous estimate by Adsley et al.

The gamma -gated proton spectra measured in the reactions 64Ni(9Be, p2n) 70Ga and 64Ni(9Be, pn) 71Ga, have been utilized to probe the collective enhancement in nuclear level density (NLD) of two oblate deformed nuclei 71Ga and 72Ga. It is seen that the gamma -gated proton spectrum are reasonably explained by using the large value of the inverse level density parameter (k = 11.2 MeV) in the NLD prescription of the Fermi gas model. The large value of k indicates rotational enhancement, which is consistent with the earlier results in other mass regions. Furthermore, a rotational enhancement factor has been included in the NLD and used in the statistical model calculation keeping the systematic value of = 8.6 MeV. It explains the gamma -gated proton spectrum nicely, which indicates the presence of collective enhancement in the NLD. The extracted enhancement factors are found to be 8.0+/-2.0 and 5.5+/-1.0 and vanish at around 15, 18 MeV excitation energies for 71Ga, 72Ga, respectively. Present observations are consistent with the previous results obtained by Pandit et al. [Phys. Rev. C 97, 041301(R) (2018)] and Mohanto et al. [Phys. Rev. C 100, 011602(R) (2019)].

The $\ensuremath{\gamma}$-gated proton spectra measured in the reactions $^{64}\mathrm{Ni}(^{9}\mathrm{Be},\mathrm{p}2\mathrm{n})^{70}\mathrm{Ga}$ and $^{64}\mathrm{Ni}(^{9}\mathrm{Be},\mathrm{pn})^{71}\mathrm{Ga}$, have been utilized to probe the collective enhancement in nuclear level density (NLD) of two oblate deformed nuclei $^{71}\mathrm{Ga}$ and $^{72}\mathrm{Ga}$. It is seen that the $\ensuremath{\gamma}$-gated proton spectrum are reasonably explained by using the large value of the inverse level density parameter ($k=11.2$ MeV) in the NLD prescription of the Fermi gas model. The large value of $k$ indicates rotational enhancement, which is consistent with the earlier results in other mass regions. Furthermore, a rotational enhancement factor has been included in the NLD and used in the statistical model calculation keeping the systematic value of $=8.6$ MeV. It explains the $\ensuremath{\gamma}$-gated proton spectrum nicely, which indicates the presence of collective enhancement in the NLD. The extracted enhancement factors are found to be $8.0+/\ensuremath{-}2.0$ and $5.5+/\ensuremath{-}1.0$ and vanish at around 15, 18 MeV excitation energies for $^{71}\mathrm{Ga}, ^{72}\mathrm{Ga}$, respectively. Present observations are consistent with the previous results obtained by Pandit et al. [Phys. Rev. C 97, 041301(R) (2018)] and Mohanto et al. [Phys. Rev. C 100, 011602(R) (2019)].

The energy loss behavior of fission fragments (FFs) from [Formula: see text]Cf(sf) in thin Mylar [Formula: see text] and Aluminium absorber foils has been revisited. The aim is to investigate the observed change in the well-known asymmetric energy of spontaneous fission of [Formula: see text]Cf as the fragments pass through increasingly thick absorber foils. Two different types of absorbers have been used: one elemental and the other an organic compound. The stopping powers have been determined as a function of energy for three fragment mass groups with average masses having [Formula: see text], 141.8, 125.8 corresponding to light, heavy and symmetric fragments of [Formula: see text]Cf. The energy loss data have been compared with the predictions of SRIM 2013 code. The best representations of the data have been achieved using the effective Z correction term in the stopping power relation from the classical Bohr theory. Using the effective charge (Z[Formula: see text]) in the stopping power relation in the classical Bohr theory best describes the stopping power data. Spectrum shape parameters, subsequently, have been extracted from the energy spectra of FFs for different foil thicknesses. The effective charge (Z[Formula: see text]) correction term determined from the stopping power data is then used in the simulation for the absorber thickness dependence of the shape parameters of the energy spectrum. The present simulation results are compared with the TRIM prediction. The trends of the absorber thickness dependence of the spectrum shape parameters, for both Mylar and Aluminium, are well reproduced with the present simulation.

The γ-gated proton spectra measured in the reactions ^64Ni(^9Be, p2n)^70Ga and ^64Ni(^9Be, pn)^71Ga, have been utilized to obtain the nuclear level density (NLD) of ^71Ga and ^72Ga nuclei by using the statistical model (SM) calculations. It is seen that the γ-gated proton spectrum are reasonably explained by using the large value of the inverse level density parameter (k = 11.2 MeV) in the NLD prescription of the Fermi gas (FG) model. The large value of k is indicative of the rotational enhancement, which is consistent with the earlier results in other mass regions. Furthermore, a rotational enhancement factor has been included in the NLD and used in the SM calculation keeping the systematic value of k=8.6 MeV and it explains the γ-gated proton spectrum nicely. The result clearly indicates the presence of collective enhancement in NLD. Subsequently, the NLD with collective enhancement has been utilized in the TALYS calculation, for the first time, to calculate the ^71Ga(n, γ)^72Ga capture cross-section. It is observed that, while the FG model without the collective enhancement in the NLD for ^72Ga under predicts the capture data, with the rotational enhancement correction the FG model over predicts the data by similar amount at higher energies. However, in the energy range of 0.01 MeV to 0.1 MeV, the FG model corrected for rotational enhancement describes the data quite well. Thus, the present work indicates that collective enhancement, whenever required, should be taken into account fro proper description of low energy capture cross section data.

Elastic scattering angular distribution for weakly bound nucleus $^{6}$Li on the deformed rare earth $^{159}$Tb target nucleus has been measured at energies around the Coulomb barrier. The elastic scattering cross sections for this reaction consist of inelastic contributions from low lying excited states of $^{159}$Tb. The pure elastic cross-sections have been extracted from the admixture of elastic and inelastic data. The optical model potential parameters for the system have been obtained from the extracted pure elastic scattering cross sections. Coupled channel calculations have been performed with this set of potential parameters, to compare the theoretical and experimental inelastic scattering cross sections. The work has been extended to obtain the spectroscopic factor for $^{158}$Tb+n configuration from the experimental 1n-pickup data.

The unstable nucleus 8Be, with its two alpha-cluster configuration, is the doorway to the formation of heavier alpha-cluster nuclei. Most importantly, its the precursor of the production of 12C through the Hoyle state, a resonance state of three alpha clusters, in the helium burning phase of a massive star. The nucleus exhibits a ground state band of rotational states established through alpha-alpha scattering experiments. A subsequent precision particle-gamma coincidence measurement of the electromagnetic transition between the 4+ -> 2+ excited states also corroborated the evidence for a highly deformed dumb-bell shaped structure of 8Be. A simultaneous phenomenological R-matrix analysis of the measured capture reaction cross sections along with the elastic excitation function and phase shift data has been performed. The resulting reduced transition strength of 21.96 +/- 3.86 e2fm4 compares well with the estimated experimental value of 21.0 +/- 2.3 e2 fm4. The R-matrix yield of the B(E2) value is closer to the prediction of cluster model but about 19% less than the ab initio result.

Quasielastic scattering excitation function at large backward angle has been measured for the weakly bound system Li-7 + Tb-159 at energies around the Coulomb barrier. The corresponding quasielastic barrier distribution has been derived from the excitation function, both including and excluding the alpha particles produced in the reaction. The centroid of the barrier distribution obtained after inclusion of alpha particles was found to be shifted higher in energy, compared with the distribution excluding the alpha particles. The quasielastic data, excluding the alpha particles, have been analyzed in the framework of continuum discretized coupled-channels calculations. The quasielastic barrier distribution for Li-7 + Tb-159, has also been compared with the fusion barrier distribution for the system.

The energy loss behaviour of fission fragments (FF) from $^{252}$Cf(sf) in thin Mylar ($H_8 C_{10} O_4$) and Aluminium absorber foils have been revisited. The aim is to investigate the observed change in the well known asymmetric energy of spontaneous fission of $^{252}$Cf as the fragments pass through increasingly thick absorber foils. Two different types of absorbers have been used: one elemental and the other an organic compound. The stopping powers have been determined as a function of energy for three fragment mass groups with average masses with $$ = 106.5, 141.8, 125.8 corresponding to light, heavy and symmetric fragment of $^{252}$Cf. Using the effective charge (Z$_{eff}$) in the stopping power relation in the classical Bohr theory best describes the stopping power data. Spectrum shape parameters, subsequently have been extracted from the energy spectra of fission fragments for different foil thickness. The effective charge (Z$_{eff}$) correction term determined from the stopping power data is then used in the simulation for the absorber thickness dependence of the shape parameters of the energy spectrum. The present simulation results are compared with the TRIM prediction. The trends of the absorber thickness dependence of the spectrum shape parameters, for both Mylar and Aluminium are well reproduced with the present simulation.

The excitation function for quasielastic scattering of the weakly bound projectile $^{6}\mathrm{Li}$ on a $^{159}\mathrm{Tb}$ target, at large backward angle, has been measured at energies around the Coulomb barrier. The corresponding quasielastic barrier distribution has been extracted from the experimental cross sections, both including and excluding the $\ensuremath{\alpha}$ particles produced in the reaction. The quasielastic scattering cross sections, excluding the $\ensuremath{\alpha}$ particles, have been analyzed in the framework of coupled channels calculations. The centroid of the quasielastic barrier distribution, including the $\ensuremath{\alpha}$ particles, is found to shift towards higher energy relative to the centroid of the fusion barrier distribution for the system. This has been attributed to the low $\ensuremath{\alpha}$-breakup threshold of the nucleus $^{6}\mathrm{Li}$.

Characterization of a hybrid telescope with gas transmission detector (ΔE) and a solid-state stop detector (E) has been fabricated for detection of low energy α particles between 5 to 1 MeV. The detector is developed for utilization in the study of alpha excitation function in (p.α) reaction. The gas ionization chamber, operated in axial field mode, measures the differential energy loss (ΔE), while the residual energies are measured by silicon detector. Particle identification is realized by implementing the ΔE-E technique. The optimum sensitivity of the detector as a telescope has been studied down to the lowest energy value of 0.89 MeV α-particles with a suitable combination of electric field and pressure or E/p value in the ionization region.

Target in nuclear physics experiment plays a crucial role in measuring the reaction cross-section, especially in nuclear astrophysics where the cross-sections are very low (∼nanobarn or picobarn) with large backgounds [1]. The nuclear astrophysics experiments rely on inverse kinematics technique to counter high background and low cross-section events [2]. However, it is difficult to make light targets such as H and He for the inverse kinematic reactions. Sometimes it is possible to produce a solid compound containing light nuclei, or build gas cells with thin windows. They may also require backing materials for mechanical stability, which contribute additional backgrounds. Therefore, these strategies may not always be appropriate because of the low density and the presence of other materials in the compound or the windows. In addition, the accurate measurement of reaction cross-section require the targets to be well confined, high density, thickness to maximize the count rates but minimize the energy loss and straggling of reaction product, etc. Therefore, making an window-less gas-jet target is only the optimal solution.

The Ne-22(p, gamma) Na-23 reaction in the Ne-Na cycle plays an important role in the production of the only stable sodium isotope Na-23. This nucleus is processed by the Ne-Na cycle during hot bottom burning (HBB) in the asymptotic giant branch (AGB) stage of low metallicity intermediate mass stars (4M(circle dot) <= M <= 6M(circle dot)). Recent measurements have addressed the uncertainty in the thermonuclear reaction rate of this reaction at relevant astrophysical energies through the identification of low lying resonances at E-p = 71, 105, 156.2, 189.5, and 259.7 keV. In addition, precise measurements of the low energy behavior of nonresonant capture have been performed and the contribution of the subthreshold resonance at 8664 keV excitation in Na-23 has been established. Here we present a systematic R-matrix analysis of direct capture to the bound states and the decay of the subthreshold resonance at 8664 keV to the ground state of Na-23. A finite-range distorted-wave Born approximation (FRDWBA) calculation has been performed for the Ne-22(He-3, d) Na-23 transfer reaction data to extract the asymptotic normalization coefficients (ANCs) required to estimate the nonresonant capture cross sections or astrophysical S-factor values in the R-matrix analysis. Simultaneous R-matrix analysis constrained with ANCs from transfer calculations reproduced the astrophysical S-factor data over a wide energy window. The value S-tot(DC) (0) = 48.8 +/- 9.5 keV b compares well with the result of Ferraro et al. and has a lower uncertainty. The resultant thermonuclear reaction is slightly larger in the 0.1 <= T <= 0.2 GK temperature range but otherwise in agreement with Ferraro et al.

Evaporated α-spectra have been measured in coincidence with low energy discrete γ-rays from residual nucleus 68Zn populated by αn evaporation from compound nucleus 73Ge produced in the reaction 64Ni(9Be,αn)68Zn at E(9Be) = 30 MeV. Low energy γ-gated α-particle spectra, for the first time, have been used to extract the nuclear level density (NLD) for the intermediate 69Zn nucleus in the excitation energy range of E ≈ 4-20 MeV. The slope of present NLD data as a function of excitation energy for 69Zn matches nicely with the slope determined from RIPL estimates for NLD at low energies and the NLD from neutron resonance data at neutron separation energy Sn. The extracted inverse NLD parameter (k = A/a˜) has been used to determine the nuclear level density parameter value a at neutron separation energy Sn for 69Zn. The cross section of 68Zn(n,γ) capture reaction as a function of neutron energy is then estimated employing the derived a(Sn) in the reaction code TALYS. It is found that the estimated neutron capture cross section agrees well with the available experimental data without any normalization. The present result indicates that experimentally derived nuclear level density parameter can constrain the statistical model description of astrophysical capture cross section and optimize the uncertainties associated with astrophysical reaction rate.

The $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction in NeNa cycle plays an important role in the production of only stable sodium isotope $^{23}$Na. This nucleus is processed by the NeNa cycle during hot bottom burning (HBB) in asymptotic giant branch (AGB) stage of low metallicity intermediate mass stats (4 M$_O$ $\leq$ M $\leq$ 6 M$_O$). Recent measurements have addressed the uncertainty in the thermonuclear reaction rate of this reaction at relevant astrophysical energies through the identification of low lying resonances at E$_p$ = 71,105, 156.2, 189.5 and 259.7 keV. In addition, precise measurements of low energy behaviour of the non-resonant capture has also been performed and the contribution of the sub-threshold resonance at 8664 keV excitation in $^{23}$Na has been established. Here, in this article, we have presented a systematic R-matrix analysis of direct capture to the bound states and the decay of the sub-threshold resonance at 8664 keV to the ground state of $^{23}$Na. A finite range distorted wave Born approximation (FRDWBA) calculation has been performed for $^{22}$Ne($^3$He,d)$^{23}$Na transfer reaction data to extract the asymptotic normalization coeeficients (ANC-s) required to estimate the non-resonant capture cross sections or astrophysical S-factor values in R-matrix analysis. Simultaneous R-matrix analysis constrained with ANC-s from transfer calculation reproduced the astrophysical S-factor data over a wide energy window. The S$_{tot}^{DC}$(0) = 48.8$\pm$9.5 keV.b compares well with the result of Ferraro, {\it et al.} and has a lower uncertainty. The resultant thermonuclear reaction is slightly larger in 0.1 GK $\le$ T $\le$ 0.2 GK temperature range but otherwise in agreeent with Ferraro, {\it et al.}.

Barrier distributions derived from fusion and back-angle quasielastic scattering excitation functions are important tools in understanding the reaction mechanisms in nucleus-nucleus collision at near-barrier energies. The excitation functions for the quasielastic scattering of Li-7 from the medium-mass target Ni-64 are measured at the angles 150. and 170. for the energy range of 12 to 24 MeV. The corresponding quasielastic barrier distribution function for this system is derived. The extracted barrier distribution is then compared with the previously measured fusion barrier distribution for the same system to look for any shift in the peak location to below-barrier energy as observed for the Li-6+Ni-64 system. Further, the barrier distributions of the system Li-7+ Ni-64 from complementary measurements of the fusion and back-angle excitation functions are compared with the barrier distribution functions of Li-6+Ni-64. While Li-6 behaves like a weakly bound projectile, another stable isotope of Li, Li-7, behaves more like a strongly bound projectile in collision with the same medium-mass target Ni-64.