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The elastic, differential and integrated, and total cross sections for the scattering of electrons and positrons by magnesium atom have been calculated. These calculations are done within the framework of complex electron/positron-atom optical potential and relativistic Dirac partial wave analysis at the impact energies 0.1–1000 eV for both the projectiles. The present results are compared with available experimental data and some other theoretical calculations.

A simple empirical formula is proposed for the rapid calculation of electron impact total ionization cross sections both for the open- and closed-shell neutral atoms considered in the range 1≤ Z≤92 and the incident electron energies from threshold to about 104 eV. The results of the present analysis are compared with the available experimental and theoretical data. The proposed model provides a fast method for calculating fairly accurate electron impact total ionization cross sections of atoms. This model may be a prudent choice, for the practitioners in the field of applied sciences e.g. in plasma modeling, due to its simple inherent structure.

The recently modified Kolbenstvedt (MKLV) model [Eur. Phys. J. D 37, 361 (2006)], developed for electron impact ionization (EII) of the K-shell atomic targets, has been extended to generalize its two parameters in terms of the electronic orbitals nl. The generalized MKLV (GKLV) with two sets of the species independent parameters for the same nl, one set for the ionization of inner orbits and another for the outermost orbit, is found profoundly successful in accounting for the EII cross section data of the K, L and M-shell neutral atoms with atomic numbers Z = 1-92 for the incident energies up to 1000 MeV in a consistent manner.

The electron impact ionization cross-sections of mono- and di-positive ionic targets are calculated using a second version of the modified binary-encounter-dipole (MBED) model, previously reported [M A Uddinet al, J. Phys. B37, 1909 (2004)]. The present version differs from the previous one in the scale factor of the Burgess denominator and is applicable to targets with chargesq = 1 and 2. The MBED in the present form is found to work well for 11 ionic targets ranging from Be+ to K+ and complements its previous version valid for targets withq s> 2

A modification of the Kolbensvedt model, MKLV, in terms of ionic, correlation (between the incident and target electrons) and relativistic corrections, is proposed to calculate the K-shell electron impact ionization cross-sections of neutral and ionic targets. The modified model, with a single set of parameters, is found to reproduce satisfactorily the experimental data for the neutral H, Al, Ar, Mn, Ge, Mo, Ag, Sn, Au, Bi and U and ionic Li + , B 4+ and O 7+ targets better than the existing empirical models from threshold energies to as high as 10 4 MeV. For the Ag target, the calculations from MKLV follow closely the results of Scofield, and for Au, those of Scofield, and Ndefru and Malik, both done in the relativistic Born approximation with the Moller interaction, at energies higher than the peak region.

A folding potential describing the $\alpha$ -scattering on 16O over a broad energy range 25.8-146.0 MeV is constructed on the basis of $\alpha$ -like cluster and unclustered-nucleon configurations of 16O. The resulting potential does not need any renormalization to fit the angular distribution of elastic cross-sections. The effects of the repulsive part of $\alpha$ - $\alpha$ and $\alpha$ -nucleon interactions are investigated. The analysis suggests that both the $\alpha$ - $\alpha$ repulsive potential and the unclustered nucleonic configuration in the target are important to describe the scattering data over a broad range of incident energies. The root-mean-square radius for the 16O nucleus is deduced.

Full finite-range macroscopic calculations in the distorted-wave Born approximation have been performed using the molecular and Michel α-nucleus potentials to analyze the angular distributions of cross-sections of the 27Al(α, d)29Si reaction, at 26.5 and 27.2 MeV incident energies, leading to seven transitions up to the excitation energy E X = 4.08 MeV of the final nucleus. The parameters of the two types of the α-nucleus potentials are determined from the elastic-scattering data. Both the molecular and Michel potentials, without any adjustment to the parameters needed to fit the elastic-scattering data, are able in most cases to reproduce, simultaneously, the absolute cross-sections particularly at large angles, where the previous calculations failed to reproduce by orders of magnitude, and the gross pattern of angular distributions of the reaction. The deuteron-cluster spectroscopic factors for most of the seven transitions, deduced using the two α-27Al potentials, differ from those obtained in earlier works. The spectroscopic factor for the ground-state transition, deduced in the present work for the 25.8 MeV data, agrees well with the shell model prediction.

Effects of three different α-nucleus potentials, the normal Woods-Saxon (WS), the squared WS and the molecular, have been studied using the differential cross-section data of inelastically scattered α-particles on 24Mg and 28Si at 54 and 26 MeV incident energies, respectively. The angular distributions of inelastic scattering to the first 2+ and 4+ states of the two nuclei have been analyzed in terms of a coupled-channel formalism. The macroscopic rotational model using both the squared WS and the molecular potentials can produce satisfactorily a simultaneous description of the elastic data and the inelastic-scattering data of the 2+ and 4+ states for both the targets. The normal WS potential fails to describe the elastic and inelastic data, simultaneously. The effects of second-order deformed potential are also investigated. Microscopic coupled-channel calculations, using the 0+-2+ coupling and the Gaussian α-nucleon interaction in the form-factor, have also been performed for the 28Si target using both the squared WS and molecular potentials, the latter one giving a reasonable description of the data.

The DWBA analyses are performed for the ground states and other strong transitions populated in the (α, t) reaction on various targets ranging fromA = 16 to 208 with zero-range and with finite-range corrections in the local energy approximation (LEA). The normalization constants without and with the LEA are found to be, respectively,D 2 0 = (18.16±3.49) × 10 MeV fm andD = (8.67±1.60)× 10 MeV2 fm3 which are reasonably consistent with some other previous studies. The normalization constants for the (α, t) reaction on the Al target are also deduced for different incident energiesEα = 25.0, 25.2, 64.5, 80.0 and 104.0 MeV for studying any possible energy dependence of the normalization constant. No tangible energy dependence was found in the present study and hence the LEA seems to be valid reliably within the energy range studied. The ratioD 2 0/D bears a value of about 2.0 which is remarkably constant over the target masses and incident energies.

Absolute magnitudes of stopping cross sections (SCS) for H+, He2+ and Li3+ in various stopping media with atomic numbers Z 2 = 2 to 100 are calculated using atomic density functions from Dirac-Hartree-Fock-Slater wave functions in the Lindhard-Schraff theory [J. Lindhard, M. Scharff, Kgl. Danske Videnskab. Selskab. Mat. Fys. Medd. 27, 15 (1953)]. The newly proposed formula, characterizing projectile-specific parameters in the incident energy range considered herein, describes satisfactorily the experimental and SRIM-simulated SCS data from low energies, with projectile velocities nearing v = Z 1 v 0 (with Z 1 as the projectile’s atomic number, v 0 = c / 137, the Bohr velocity and c, the speed of light in vacuum), to high energies up to about 2.5 MeV/u.

A search is made to identify hypernuclear species with two or more decay centres in nuclear emulsion exposed to a separated beam of 3.0 GeV/c K−-mesons at the CERN Proton Synchrotron. In a sample of 493 hypernuclei one event has been observed whose most probable interpretation turns out to be31SiΛΛ with the successive decay modes Open image in new window and binding energyBΛΛ=(38.2±6.3) MeV.

In a systematic search for rare hypernuclear species in nuclear emulsion exposed to 3.0 GeV/c K−-mesons at the CERN PS, an event with three connecting stars has been observed. The two secondary stars are most probably due to the decay of a cascade hypernucleus according to the following channel: \(_\Xi ^{13} - C \to {}_\Lambda ^8 Be + {}_\Lambda ^5 He + Q\). The binding energy of the ÷-hypernucleus is \(B_{\Xi - } \left( {_{\Xi - }^{13} C} \right) - \left( {18.1 \pm 3.2} \right)\) MeV.