Vol 82, No 4 (2019)

Dynamic neutron diffraction on perfect InSb crystals is analyzed theoretically both under conditions of predominantly potential scattering and under conditions of predominantly resonant scattering. Attention is given primarily to the effect of anomalous neutron transmission. A project of an experiment aimed at studying this effect in predominantly resonant neutron scattering via a simultaneous detection of reflected and transmitted beams and secondary gamma rays is proposed. It is shown that such an experiment may be performed in beams from high-flow reactors.

The probability of a reaction’s occurrence is known as reaction cross section which provides researchers numerous benefits and details to generate advanced studies. Although it is possible to obtain this value experimentally, it may not be achievable to have it due to some physical events that occur in low-energy situations. In such cases, where the Coulomb repulsion between the target and incident particle becomes more dominant, a rescaled variant of cross section which is S factor could be usable. In this study, S-factor calculations have been performed for ¹¹²Sn(p, γ)¹¹³Sb, ¹¹⁴Sn(p, γ)¹¹⁵Sb, ¹¹⁶Sn(p, γ)¹¹⁷Sb, ¹¹⁹Sn(p, γ)¹²⁰Sb, ¹¹³In(p, γ)¹¹⁴Sn, and ¹¹⁵In(p, γ) ¹¹⁶Sn reactions by using computer aided calculation codes EMPIRE 3.2 and TALYS 1.8. The effects of gamma strength function over the S-factor value’s calculation with TALYS 1.8 code have also been investigated. To comment about the reached outcomes, calculation results have been compared with the data taken from Experimental Nuclear Reaction Data Library (EXFOR) both visually by graphing and statistically by variance analysis.

The spectra of ^3,4He charged particles produced in stopped pion absorption by nuclei were measured for 17 nuclei in the mass-number range of 6 ≤ A ≤ 209 by means of a semiconductor spectrometer. These data were analyzed on the basis of a phenomenological model where the absorption reaction in question is treated as a three-stage process: primary absorption by intranuclear clusters, preequilibrium stage, and evaporation stage. It is shown that a dominant contribution to the production of helium isotopes with energies not less than 20 MeV comes from the preequilibrium stage. The contribution of the knockout and pickup mechanisms to ^3,4He production is estimated.

A self-consistent approach in the problem of taking into account quasiparticle-phonon interaction provides a high predictive power and is free from adjustable parameters (this is of crucial importance for astrophysics). Moreover, it is consistent and makes it possible to take into account new effects. A brief survey of the results obtained within this approach on the basis of Skyrme or Fayans functionals by employing the smallness parameter g², where g is the phonon-production amplitudes, with allowance for tadpole effects is presented. The contribution of quasiparticle-phonon interaction to ground-state electromagnetic moments of odd nuclei; second-order anharmonic effects in g², including quadrupole moments of the first 2⁺ and 3⁻ states and EL transitions between one-phonon states; third-order anharmonic effects; pygmy dipole and giant resonances; and the contribution of quasiparticle-phonon interaction to radiative properties of nuclear reactions are considered. For magic and semimagic nuclei, additional effects and structures arising in nuclear features because of quasiparticle-phonon interaction are discussed along with new—that is, three- and four-quasiparticle ground-state—correlations. Earlier unknown values of the above features, including the features of the pygmy dipole resonance in neutron-rich nickel isotopes, are predicted. It is shown that, in all of the aforementioned problems, the contributions of quasiparticle-phonon interaction is sizable, is of fundamental importance, and is necessary for explaining experimental data.

Within a dynamical approach, the average spins of fission fragments originating from the ¹²C + ^235,236U and ¹³C + ²³⁵U complete fusion reactions at c.m. energies in the range of E_c.m. = (55–75) MeV are analyzed as a function of energy. Particular attention is given to the process of formation of initial distributions for the components of the total angular momentum of compound nuclei. It is shown that substantial distinctions in the behavior of average spins of fission fragments for different fusion reaction channels are expected to be observed in the range of subbarrier energies.

The differential cross sections for the elastic scattering of π^± and K⁺ mesons on ^13,15C and ¹⁵N nuclei at intermediate energies were calculated within Glauber diffraction theory. The sensitivity of the calculated features to variations in the target wave functions and in the multiple-scattering contribution were analyzed. The contribution of double scattering were estimated.

Extensive air showers characterized by a multicomponent time structure were detected at the experimental Horizon-T array deployed at the Tien Shan High-Altitude Science Station of Lebedev Physical Institute, Russian Academy of Sciences, at an altitude of 3346 meters above sea level. Such a structure manifested itself in showers of energy above 10¹⁷ eV and suggests that, in contrast to the standard mechanism of the development of a nuclear-electromagnetic cascade, shower particles reach the observation level as components of several shower disks.