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The electromagnetic form factors of the proton and the neutron in the timelike region are investigated. Electron–positron annihilation into antinucleon-nucleon ( N ¯ N) pairs is treated in distorted wave Born approximation, including the final-state interaction in the N ¯ N system. The latter is obtained by a Lippmann–Schwinger equation for N ¯ N potentials derived within SU(3) chiral effective field theory. By fitting to the phase shifts and (differential) cross section data, a high quality description is achieved. With these amplitudes, the oscillations of the electromagnetic form factors of the proton and the neutron are studied. It is found that each of them can be described by two fractional oscillators. One is characterized as "overdamped" and dominates near the threshold, while the other is "underdamped" and plays an important role in the high-energy region. These two oscillators are essential to understand the distributions of polarized electric charges induced by hard photons for the nucleons. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to determine values of the asymptotic normalization coefficients for the virtual decays 6He+p → 7 Li(g.s.) and 6He+p → 7 Li(0.48 MeV). For this purpose, the recently measured experimental differential cross-section of the proton transfer reaction d(6He,7Li)n has been analyzed. The modified distorted wave born approximation is used to determine the values of the asymptotic normalization coefficients. The peripheral character of this reaction has been tested. It has been shown that this reaction is peripheral. New values of the asymptotic normalization coefficients for the virtual decays 6He+p → 7 Li(g.s.) and 6He+p → 7 Li(0.48 MeV) with their uncertainties have been obtained. [ABSTRACT FROM AUTHOR]

The available experimental data for the elastic scattering of isobar nuclei 6Li and 6He on 1 2 C nuclei have been reanalyzed in a wide energy range of energy from 5.8 MeV to 600 MeV using the optical model with Distorted Wave Born Approximation (DWBA), and coupled reaction channel method (CRC) where inelastic scattering and transfer have been involved during calculations. A semi-microscopic potential, namely double-folding cluster model (DFC) has been used to investigate the cluster structure for both projectiles and target which was folded with Distorted Wave Born Approximation (DWBA) as a real part of potential where the imaginary part was taken in Woods–Saxon (WS) shape. The crystal model method has been applied to 6Li, 6He elastically scattered by 1 2 C, and reliable analysis of the considered experimental data has been obtained. [ABSTRACT FROM AUTHOR]

Nuclear reaction rates are one of the most important ingredients in describing how stars evolve. The study of the nuclear reactions involved in different astrophysical sites is thus mandatory to address most questions in nuclear astrophysics. Direct measurements of the cross-sections at stellar energies are very challenging–if at all possible. This is essentially due to the very low cross-sections of the reactions of interest (especially when it involves charged particles), and/or to the radioactive nature of many key nuclei. In order to overcome these difficulties, various indirect methods such as the transfer reaction method at energies above or near the Coulomb barrier are used to measure the spectroscopic properties of the involved compound nucleus that are needed to calculate cross-sections or reaction rates of astrophysical interest. In this review, the basic features of the transfer reaction method and the theoretical concept behind are first discussed, then the method is illustrated with recent performed experimental studies of key reactions in nuclear astrophysics.

The in-plane magnetic structure of a layered system with a polycrystalline grain size less than the ferromagnetic exchange length was investigated using polarized neutron off-specular scattering and grazing incidence small angle scattering measurements to gain insight into the mechanism that controls the magnetic properties which are different from the bulk. These complementary measurements with different length scales and the data analysis based on the distorted wave Born approximation revealed the lateral correlation on a length scale of sub- μm due to the fluctuating orientation of the magnetization in the layer. The obtained in-plane magnetic structure is consistent with the random anisotropy model, i.e. competition between the exchange interactions between neighboring spins and the local magnetocrystalline anisotropy. [ABSTRACT FROM AUTHOR]

The angular distribution measurements for 16O ion beam elastically scattered from 11B target of thickness 32.9μg/cm2 at energy 22.4 MeV had been performed in the cyclotron DC-60 INP NNC RK. The previous measurements for 16O+11B nuclear system at energies 27, 30, 32.5 and 35 MeV showed an increase in the differential cross-section at backward angles due to the contribution of cluster transfer. Such transfer process could not be described in terms of optical model (OM); it could be described within the framework of distorted wave Born approximation method implemented in FRESCO code. Both one (5Li) and two-step transfer (proton transfer followed by Alpha transfer) were taken into considerations. We have extracted the spectroscopic amplitude (SA) for the configuration 16O→11B+5Li. [ABSTRACT FROM AUTHOR]

We have measured the angular distributions for 16O elastically scattered on 12C nuclei at energy 28 MeV and also for 12C ion beam elastically scattered on 11B target nuclei at energy 18 MeV. These measurements were performed in the cyclotron DC-60 INP NNC RK. Calculations were performed using both empirical Woods-Saxon and double folding optical model potentials. Both elastic scattering and transfer reaction were taken into consideration. We have extracted the spectroscopic factors for the configurations 16O → 12C + α and 12C → 11B + p and compared them with other calculated or extracted values at different energies from literature. The extracted spectroscopic factor for the configuration 12C → 11B + p from the current work is in the range 2.7-3.1, which is very close to Cohen-Kurath prediction. While for the configuration 16O → 12C + α, spectroscopic factors show fluctuation with energy which could be due to the well-known resonant-like behavior observed in 16O + 12C excitation function. [ABSTRACT FROM AUTHOR]

Abstract: The second-order distorted wave Born approximation (DWBA) method is employed to investigate the triple differential cross sections (TDCS) of coplanar doubly symmetric collisions for alkali target sodium at excess energies of 6–60 eV. Comparing with the first-order DWBA calculations, the inclusion of second-order Born term in the scattering amplitude improves the degree of agreement with experiments, especially for backward scattering region of TDCS. This indicates the present second-order Born term is capable to give a reasonable correction to DWBA model in studying coplanar symmetric problems in low and intermediate energy range. [Copyright &y& Elsevier]

A formalism is presented which allows the quantitative evaluation of data from grazing-incidence small-angle neutron and X-ray scattering - GISANS and GISAXS - in the framework of the distorted wave Born approximation. While several aspects have been reported previously, this formalism combines solutions for scattering intensities in both reflection and transmission hemispheres, taking into account instrumental resolution effects. This formalism is applied to the case of GISANS from self-organized diblock copolymers, ordered in perpendicular lamellar structures on an Si wafer in randomly oriented short-range-ordered regions. The periodicity of D = 85 (9) nm found for deuterated polystyrene-polybutadiene of molecular weight Mw = 165 kg mol−1 and a molecular weight fraction of the deuterated polystyrene block of 52% is consistent with atomic force microscopy and specular neutron reflectivity results. [ABSTRACT FROM AUTHOR]

Abstract: The triple differential cross sections for (e, 2e) ionization of sodium in a coplanar symmetric geometry have been studied in distorted wave Born approximation with the modified semiclassical exchange potential. The present calculations improve the agreement between the theoretical and experimental results. The post-collision interaction and target polarization effects have also been studied. In addition, the variation trends of the shape and ratio for the forward and backward scattering peaks have been discussed. Besides, the small bump observed between these two peaks has been analyzed by the interaction between active electron and passive electrons. [Copyright &y& Elsevier]

Progress in breakup reaction theories, like the distorted wave Born approximation, the continuum discretized coupled channels method and the dynamical eikonal approximation, is brought into focus. The need to calculate exclusive reaction observables and the utility of benchmark tests as arbitrators of theoretical models are discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this Letter we report the results of our calculations using the Modified Semiclassical Exchange Approximation in the Distorted Wave Born Approximation to determine the cross section for Potassium. The results are compared with the experimental and theoretical studies. The effect of post collision interaction has also been studied. [Copyright &y& Elsevier]

Abstract: Nanoscience and nanotechnology are tremendously increasing fields of research that aim at producing, characterizing and understanding nanoobjects and assemblies of nanoobjects. Their new physical or chemical properties, which arise from confinement effects, intimately depend on their morphological properties, i.e. their shapes, their sizes and their spatial organization. This calls for dedicated morphological characterization tools, among which is the Grazing Incidence Small Angle X-Ray Scattering (GISAXS). This reciprocal space technique has emerged in the last two decades as a powerful tool that allows investigating in a non-destructive way the morphological properties from one to billions of nanoparticles, either on a surface, or embedded in a matrix, with sizes ranging from 1 nm to several microns. The advantages of the technique are that it is non-destructive; it yields statistical information averaged on a large number of nanoparticles; it allows probing both the surface or deep below it, by changing the incident angle of the X-ray beam; it can be used in very different sample environments, in particular in situ in the course of a given process such as growth, annealing, gas exposure; and it may be given chemical sensitivity by use of anomalous scattering. This report presents a review of the GISAXS technique, from experimental issues to the theories underlying the data analysis, with a wealth of examples. The physical morphological information contained in GISAXS data and its analysis are presented in simple terms, introducing the notions of particle form factor and interference function, together with the different cases encountered according to the size/shape dispersion. The theoretical background of X-ray diffuse scattering under grazing incidence is presented in a general way, and then applied to the particular case of grazing incidence small angle X-ray scattering from assemblies of particles either on a substrate, or buried below it. Most of the GISAXS measurements published to date are reported, covering the fields of ex situ studies of embedded metallic nanoparticles, granular multilayered systems, implanted systems, embedded or stacked or deposited semi-conductor nanostructures, porous materials and copolymer thin films. A special emphasis is brought on in situ experiments, performed either in ultra-high vacuum during nanoparticle growth by molecular beam epitaxy, or in gas-reactors during catalytic reactions. This covers a very broad field, from (i) the 3D island (Volmer–Weber) growth of metals on oxides surfaces to (ii) the organized growth of metals on surfaces that are nanopatterned either by surface reconstruction or by underlying dislocation networks or by deposit-induced nanofacetting, to (iii) the in situ investigation of the self-organized Stranski–Krastanow hetero-epitaxial growth of semi-conductor quantum dots on semi-conductor surfaces, or (iv) the in situ surface nanopatterning by ion bombardment. Many examples are discussed in detail, to illustrate the large diversity of systems and morphologies that can be addressed as well as the different analysis issues and the conclusions of the technique in terms of growth mode. [Copyright &y& Elsevier]

Abstract: Calculations of the triple differential cross section (TDCS) for electron impact ionization of the Ar (3s) orbital in a coplanar asymmetric geometry, using modified distorted wave Born approximation (DWBA) methods, are reported. The role of the polarization effect in collisions of Ar (3s) is considered in the calculations, and the calculated results show that the polarization potential is quite important. [Copyright &y& Elsevier]

Abstract: The spectroscopic-factor amplitudes for the triton-cluster transfer are used in distorted wave born approximation (DWBA) analyses for the first six 12C states, up to Ex =17.76MeV, in the reaction 15N(p, α) for E p=9.09–43.7MeV. Agreements are obtained for most 12C states between the theoretically predicted spectroscopic factors (S) and both of experimental and theoretical forward integrated cross-section values (at E p∼43.7MeV) and their sequence states with the same nuclear parameters. The theoretical spectroscopic factors failed to predict the transition strengths for the two 12C states at 7.6542 and 17.76MeV, while the DWBA predictions failed to reproduce the strengths of the three 12C states at 7.6542, 14.083 and 17.76MeV. This is probably, in the first case, due to the inclusion of other direct mechanisms and (or) to the multi-step processes in their mechanism, while for the second case, it is may be due to either the angular momentum mismatching effect or the choice of the optical parameters. The agreement between theoretical and experimental data for the first six investigated 12C states indicate the success of the Cohen–Kurath wave-functions itself and their accuracy. They also indicate the success of the model of calculations of spectroscopic factors. [Copyright &y& Elsevier]

Abstract: Calculations of the triple differential cross section (TDCS) for electron impact ionization of the Ar(2p) orbital in a highly asymmetric geometry, using modified distorted wave Born approximation (DWBA) methods, are reported. The role of the polarization effect in (e, 2e) collisions of Ar(2p) is considered in the calculations, and the calculated results shows that the polarization potential is particularly important. [Copyright &y& Elsevier]

The Trojan–Horse method is an indirect approach to determine the energy dependence of S factors of astrophysically relevant two-body reactions. This is accomplished by studying closely related three-body reactions under quasi-free scattering conditions. The basic theory of the Trojan–Horse method is developed starting from a post-form distorted wave Born approximation of the T-matrix element. In the surface approximation the cross-section of the three-body reaction can be related to the S-matrix elements of the two-body reaction. The essential feature of the Trojan–Horse method is the effective suppression of the Coulomb barrier at low energies for the astrophysical reaction leading to finite cross-sections at the threshold of the two-body reaction. In a modified plane wave approximation the relation between the two- and three-body cross-sections becomes very transparent. The appearing Trojan–Horse integrals are studied in detail. [Copyright &y& Elsevier]