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We have studied the electron emission angular distributions for single ionization of helium atoms in their ground states induced by fast proton impact in coplanar geometry. We have employed the four-body formalism of distorted wave (DW-4B) approximation to calculate the fully differential cross sections (FDCS) of the ejected electron for several values of the momentum transfer and energies of the electrons ejected in the scattering plane. In this formalism, distortion in the exit channel related to the Coulomb continuum states of the scattered proton and the ejected electron in the field of residual target ion are included. In the entrance channel, the initial bound state wavefunction is distorted by the incoming proton and the corresponding wavefunction is related to the Coulomb continuum state of the active electron and the proton. The transition amplitude contains nine-dimensional integrals, and it is analytically reduced to two-dimensional integrals. These two-dimensional integrals can be calculated numerically. The influence of the target wavefunctions on the FDCS is also investigated using various bound-state wavefunctions for the helium atom. The obtained results using the DW-4B approximation have been compared with the recent measurements of Schulz et al. (Phys Rev A 73:062704, 2006), Gassert et al. (Phys Rev Lett 116:073201, 2016) and Chuluunbaatar et al. (Phys Rev A 99:062711, 2019) and with the other theoretical calculations. It is found that in the whole angular range clear discrepancies are found between the experimental data and the theoretical predictions at large momentum transfer and intermediate impact energy. [ABSTRACT FROM AUTHOR]

The nuclear matter parameters define the nuclear equation of state (EoS), they appear as coefficients of expansion around the saturation density of symmetric and asymmetric nuclear matter. We review their correlations with several properties of finite nuclei and of neutron stars within mean-field frameworks. The lower order nuclear matter parameters such as the binding energy per nucleon, incompressibility and the symmetry energy coefficients are found to be constrained in narrow limits through their strong ties with selective properties of finite nuclei. From the correlations of nuclear matter parameters with neutron star observables, we further review how precision knowledge of the radii and tidal deformability of neutron stars in the mass range 1 - 2 M ⊙ may help cast them in narrower bounds. The higher order parameters such as the density slope and the curvature of the symmetry energy or the skewness of the symmetric nuclear matter EoS are, however, plagued with larger uncertainty. From inter-correlation of these higher order nuclear matter parameters with lower order ones, we explore how they can be brought to more harmonious bounds. [ABSTRACT FROM AUTHOR]

We have studied ionization and electron capture cross sections for single-electron removal from biological molecules (adenine, cytosine, guanine, thymine, and uracil) by proton impact at energies ranging from 30 keV/amu to 10 MeV/amu. In this investigation, the three-body distorted wave method is used. The calculations are based on the independent electron model. For electron capture process, distortion in the final channel related to the Coulomb continuum states of the active electron and the projectile in the field of residual target ion is included. In case of ionization, we take all the pair-wise Coulomb interactions, which treat all interactions on equal footing in the final channel. Moreover, the asymptotic Coulomb logarithmic phase for the relative motion of two colliding nuclei is included in the initial channel. In both processes, the molecular character of the biological target is assumed to be a linear combination of their atomic orbitals (LCAO) and, for all cases, the different atomic orbitals are described with the Roothaan-Hartree-Fock (RHF) approximation. We have also calculated the total capture cross sections using simple Bragg's additivity rule. For electron capture, the contributions to the TCS from the core orbitals of the molecule have also been explicitly analyzed. The double differential cross sections (DDCS) for electron emission as well as the total cross sections for single ionization of only uracil molecule with fast proton impact are also calculated. The results for capture and ionization cross sections are compared with other theoretical calculations and existing experimental data. We find that our calculated results are in quite better agreement with available experimental data than the other theoretical results. [ABSTRACT FROM AUTHOR]

A theoretical study of the double-differential cross sections (DDCS) for ejection of electron from hydrogen atom in ground state by the impact of C 6 + ion with energy values 1 and 2.5 MeV/amu is presented. For the final state, we use a continuum distorted wave that contains the product of two Coulomb distortions due to the projectile–electron and target–electron Coulombic interactions for which it is called the two-Coulomb-wave (2CW) model. In this paper, the energy and angular distributions of DDCS for electron emission from atomic hydrogen have been investigated. The ejected electrons are influenced by the combined fields of the target and the projectile ion. Comprehensive comparisons are made between the three-Coulomb-wave model (Jana et al. in Eur Phys J D 66:243, 2012) and the present 2CW model. The emitted electron, the incident projectile ion and the residual ion are considered to be in the same plane. It is found that the two-centre effect has a major influence on the observed forward–backward angular asymmetry in the angular distribution of electron emission spectra. The region of the binary encounter peak is analysed in detail. The present computed results have been compared with the available experimental results as well as other theoretical calculations based on the first Born approximation and the continuum distorted wave eikonal initial state approximation. Moreover, the present computed results are in better agreement with the available experimental data for electron emission cross sections. [ABSTRACT FROM AUTHOR]

The single ionization of He atom by the impact of highly charged dressed projectile nucleus is investigated by applying the three-body formalism of three-Coulomb wave (3CW) model and the first Born approximation (FBA). In the 3CW formalism, the interaction between the dressed projectile and the active electron is represented by a model potential containing both the long-range and short-range part of the Coulomb potential. The target is treated as a one-electron atom, where the interaction of the active electron with the rest of the target is represented by a similar type of model potential. The correlated motion of each pair of particles, interacting through long-range Coulomb potential, is taken into account in the final state. In addition, an independent particle model and a single-zeta Roothaan-Hartree-Fock 1s wavefunction, describing helium in its ground state, is used to carry out the calculations, where the effective charge of the target nuclei is obtained from the initial orbital energy. The energy distributions of the double-differential cross sections (DDCS) at low and intermediate energy electron emission from helium atom have been investigated. Our theoretical results are compared with both the available experimental measurements and theoretical calculations using other methods. There is good overall agreement of the present calculations with experimental data except for low-energy electron emission (less than 10 eV). For target ionization by a dressed projectile, we find that the cross sections depend on the projectile charge. For distant collisions involving high energy ions, the primary effect of bound projectile electrons is to screen the projectile nuclear charge, thereby reducing the strength of the interaction potential. Finally, the energy distribution of DDCS ratio at different angles has also been studied. [ABSTRACT FROM AUTHOR]

Total as well as angular-differential cross sections for single electron capture have been investigated in collision of bare ions ( H + , H e 2 + and L i 3 + ) with hydrogen molecules at intermediate and high collision energies with special emphasis on finding interference effects to be exhibited by angular-differential cross sections. Here, we apply the first-order molecular target continuum distorted-wave approximation. Within the distorted-wave formalism, the one-active-electron model, developed to describe collisions with multi-electronic atomic targets, has been employed for the case of H 2 targets. Here, distortion in the final channel related to the Coulomb continuum state of the active electron in the field of residual molecular target ion is included. The present computed results are compared with the available experimental and other theoretical results. The total cross section is obtained by integrating over the projectile's scattering angle and averaging over all the molecular orientations. The total capture cross sections for all the projectile ions have fair agreement with the experimental observations particularly at lower projectile energies. We have studied the differential cross sections at θ ρ = 90 ∘ , ϕ ρ = 0 ∘ , where θ ρ and ϕ ρ are the polar and azimuthal angles, respectively, of the molecular axis with respect to the incident direction at different impact energies. The interference between two capture amplitudes associated with two centers in the molecule has been found to be more pronounced at fixed orientation of the molecule. [ABSTRACT FROM AUTHOR]

In this work, we report theoretical electron capture cross sections for single-electron removal from molecules of biological interest and noble gases by bare ion (H+ and He2+) impact at energies ranging from 25 to 10,000 keV/amu. We use a distorted wave (DW) method where the intermediate continuum state of the active electron with the target ion has been taken into account. This method is developed within the framework of the independent electron model taking particular care of the representation of the bound continuum target states. Two different approximations have been considered for molecular targets: molecular representation of the bound-state target wavefunction and Bragg's additivity rule. The molecular orbital for targets are described within the framework of the complete neglect of differential overlap (CNDO) method based on the linear combination of atomic orbital (LCAO) approximation. Using the DW method, we have also calculated the K-, L- and M- shell electron capture in collisions of bare ions with three noble gases He, Ne, and Ar respectively. Contributions from different molecular orbitals and different shells to the total cross sections (TCS) are studied. The preference of electron capture occurs in accordance as the binding energy of the active electron in molecular orbital and atomic shell. The maximum contributions to TCS for SC comes from the less bound electrons in repetitive orbitals, whereas the tightly bound electrons dominate the TCS at higher projectile energy regime. Variation of TCS with impact energy are compared with the available experimental observation and other theoretical findings. We find that the present theoretical method is satisfactory in both intermediate and high-energy region for molecules as well as noble gas targets to give reliable outcomes compared to other theoretical methods. [ABSTRACT FROM AUTHOR]

The nature of equation of state for the neutron star matter is crucially governed by the density dependence of the nuclear symmetry energy. We attempt to probe the behaviour of the nuclear symmetry energy around the saturation density by exploiting the empirical values for volume and surface symmetry energy coefficients extracted from the precise data on the nuclear masses. [ABSTRACT FROM AUTHOR]

Based on the general analysis of the grand canonical partition function in the S-matrix framework, a method is presented to calculate the equation of state of dilute warm nuclear matter. The result is a model-independent virial series for the pressure and density that systematically includes contributions from all the ground and excited states of all the stable nuclear species and their scattering channels. The multiplicity distribution of these species to keep the matter in statistical equilibrium is found out and then the pressure, incompressibility and the symmetry energy of the system are evaluated. The calculated symmetry energy coefficients are found to be in fair agreement with the recent experimental data. [ABSTRACT FROM AUTHOR]

Fragmentation is expected to be an experimental signal which can give some information about the physical characteristics of finite excited systems. We try to investigate the question concerning the mechanism which governs the onset of the disassembly of such systems in connection with their internal dynamics. We restrict this study to the case where the systems are in thermodynamical equilibrium. We use the 2-dimensional Ising model as a generic model in order to calculate the multiplicities for the formation of strongly bound clusters inside the system and analyse their behaviour as a function of the temperature. The calculated observables show features which reflect the role played by the internal dynamics. The evolution of the shape of the cluster multiplicities with temperature obtained in the present study is qualitatively the same as the one which comes out through different nuclear phase space fragmentation models. [ABSTRACT FROM AUTHOR]

The dependence of the inclusive variances σ, σ and σ in nuclear collisions is investigated as a function of the correlation coefficient ρ for isospin correlated nuclon exchange on the dinuclear potential energy surface (PES). Variances for neutron-proton cluster exchange (single step process with zero net momentum between the constituents) are also evaluated. This analysis is helpful to understand the nature of the exchange mechanism. There exist a few experimental data which are at variance with either uncorrelated neutron-proton exchange or with isospin correlated exchange. An explanation of this data may possibly lie in coexisting neutron-proton cluster exchange. [ABSTRACT FROM AUTHOR]

The formation of the neck in the entrance channel is studied using a classical dynamical model. The dependence of neck radius on bombarding energy, mass or charge and angular momentum is discussed. [ABSTRACT FROM AUTHOR]

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Copyright of Il Nuovo Cimento della Societa Italiana di Fisica: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Linearized hydrodynamic equations together with Maxwell's equations are used to describe a compressible partially ionized plasma interacting with a weak electromagnetic field. Using this fluid description of a plasma, orthogonality properties of modes are investigated for a compressible, partially ionized plasma. This plasma is confined in a uniform cylindrical structure of arbitrary cross-section, in the presence or absence of a static magnetic field along the axial direction. The modes in the plasma are found to be orthogonal provided they satisfy the following conditions: a) the electromagnetic field must satisfy the usual known impedance boundary conditions, and b) the pressure is proportional t o the normal component of the velocity of the fluid elements (i.e., plasma elements) at the boundary in a particular way which may be termed the 'hydrodynamic impedance boundary condition'. [ABSTRACT FROM AUTHOR]

The scattering of plane waves with two types of polarization by a circular homogeneous anisotropic cylinder at oblique incidence is investigated. The anisotropy of the medium is characterized by suitable dyadic forms of ε and μ, which may represent a uniform plasma column or a uniform ferrite column in the presence of a uniform static magnetic field in the axial direction. In the general problem, expressions for fields inside and outside the cylinder are obtained and the total scattering cross section is evaluated. From the general problem various special cases are obtained by the limiting process and checked with known results. Total scattering cross sections for various parameters have been calculated numerically on a digital computer for normal indidence only. A study of these numerical results show the feasibility of an anisotropic plasma column as an electronic scanning antenna. [ABSTRACT FROM AUTHOR]