Total cross sections for fission of heavy nuclei by intermediate-energy protons

The results of measuring total cross sections for proton-induced fission of ^natPb, ²⁰⁹Bi, ²³²Th, ²³³U, ²³⁵U, ²³⁸U, ²³⁷Np, and ²³⁹Pu nuclei at proton energies from 200 to 1000 MeV are reported. The measurements were carried out in steps of ≈100 MeV. Complementary fission fragments were detected in coincidence by two parallel-plate avalanche gas counters placed in the beam line on both sides of the thin target close to it. Energy and isotope dependences of the fission cross sections are analyzed.     

Investigation of near-threshold eta-meson production in the reaction π ? p→ ηn

Differential and total cross sections for eta-meson production in the reaction ?? ^? p ?? ??n were measured within the experimental program eta-meson physics implemented in the pion channel of the synchrocyclotron of the Petersburg Nuclear Physics Institute (PNPI, Gatchina). These measurements were performed at incident-pion momenta (700, 710, 720, and 730 MeV/c) in the vicinity of the threshold for the process under study by using the neutral-meson spectrometer designed and created at the Meson Physics Laboratory of PNPI. It is shown that, in the immediate vicinity of the threshold (685 MeV/c), the process of eta-meson production proceeds predominantly via S ₁₁(1535)-resonance formation followed by the decay S ₁₁(1535) ?? ??n (the respective branching fraction is Br ?? 60%), but that, as the momentum of incident pions increases, the role of the D wave becomes ever more important. A detailed analysis of this effect indicates that it is due to the increasing contribution of the D ₁₃(1520) resonance. Although the branching fraction of the decay of this resonance through the ??n channel is assumed to be very small (BR ?? 0.24%), the effect is enhanced owing to the interference between the D wave and the dominant resonance S ₁₁(1535).     

Study of Inelastic $$\boldsymbol{A}$$ ( $$\boldsymbol{p,p^{\prime}}$$ ) $$\boldsymbol{X}$$ Reaction with $${}^{\mathbf{9}}$$ Be and $${}^{\mathbf{90}}$$ Zr Nuclei at 1 GeV

Physics of Atomic Nuclei - The secondary proton polarization and differential cross sections of the ( $$p,p^{\prime}$$ ) inelastic reaction on nuclei $${}^{9}$$ Be and $${}^{90}$$ Zr at the initial...     

Infrared spectra of molecular chlorine complexes with acetylene,ethylene and propylene at low temperatures

Infrared spectra of molecular complexes of C₂H₂Cl₂, C₂D₂Cl₂, C₂H₄Cl₂, C₂D₄Cl₂, and C₃H₆Cl₂ were obtained after simultaneous slow deposition of both components on the cooled window of an optical cryostat at 75°K. Chlorine addition reactions to the multiple bond start in these systems at 90–100°K.     

Formation of soot clusters under the action of electric field of direct-current corona during combustion of natural gas

The influence of the electrode type and geometry, the interelectrode distance, and the electric field strength on the yield and distribution of soot particles during the combustion of natural gas in an electric field of direct-current corona discharge for positive and negative electrodes has been studied. The results are interpreted with allowance for the ion wind effect. The structure of soot clusters has been examined by electron microscopy.     

Polarization in quasielastic (p,2p) scattering on a 4He nucleus at 1 GeV

The polarization of secondary protons from the (p, 2p) reaction induced by 1-GeV protons incident to a ⁴He nucleus was measured in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons from this reaction were recorded in coincidence at unequal scattering angles of Θ₁ = 18°?24.21° and Θ₂ = 53.22° over a broad range of the recoil-nucleus momentum K _B between 0 and 150 MeV/c. It was found that the measured polarization of either secondary proton is less than that observed in free elastic proton-proton scattering. The magnitude of this difference is determined by the mean binding energy of s-shell protons rather than by the effective nuclear density. The polarizations measured in inclusive quasielastic and elastic scattering of 1-GeV protons on ⁴He nuclei are presented for scattering angles in the range Θ₁ = 18° ? 24.21°.     

Measurement of the polarization correlation parameter C nn in the pp elastic scattering with an unpolarized proton target and an unpolarized 1-GeV proton beam

The polarization correlation parameter C _nn in the elastic proton-proton scattering was for the first time measured with a high statistical accuracy at 1 GeV using an unpolarized proton beam incident on an unpolarized proton target. Both outgoing protons from the reaction were detected in coincidence by means of a two-arm focusing magnetic spectrometer installed at nonsymmetric angles corresponding to the center-of-mass scattering angle Θ_cm = 62.25°. The correlation parameter C _nn , as well as polarizations P ₁ and P ₂ of the secondary protons, were measured by means of multiwire proportional chamber polarimeters placed at the focal planes of each spectrometer arm. The obtained data are compared with the predictions of the phase-shift analysis. The connection with the experiment on C _nn and polarization measurements in the (p, 2p) reaction on ⁴He and other light nuclei in similar kinematics is discussed