V. M. Lebedev

αγ angular correlations in the inelastic scattering of α particles on 24Mg at Eα = 30.3 MeV

The results from measuring the angular dependence of differential α-scattering cross sections on 24Mg with final nucleus formation in the ground and three lower excited states are presented, along with the double differential 24Mg(α, αγ)24Mg(2+, 1.369 MeV) reaction cross sections at Eα = 30.3 MeV. The spin-tensor components of the density matrix of the 24Mg nucleus in the 2+(1.369 MeV) state are reconstructed and its orientation characteristics are determined. The experimental results are compared to theoretical results under the assumption of collective excitation and mechanisms for compound nucleus formation.

Investigation of the mechanism of inelastic deuteron scattering on 12C at E d = 15.3 MeV by the method of dγ angular correlations

The results are presented that were obtained by measuring the differential cross sections for the reaction 12C(d,d) 12C occurring at Ed = 15.3 MeV and leading to the production of a 12C nucleus in the ground and the first excited state. The energy dependences of the differential reaction cross sections were measured for three angles of deuteron emission in the range of projectile-deuteron energies Ed between 12 and 15.3 MeV. The double-differential cross sections for the reaction in question were measured for the 2+ state of the 12C nucleus at 4.44 MeV, and the angular dependences of the even spin-tensor components of the density matrix were determined, along with the angular dependences of the populations of magnetic sublevels and the components of the tensors of multipole-moment orientation. These experimental results are compared with their theoretical counterparts obtained under the assumption of various reaction mechanisms, including collective interaction, heavy-particle stripping, a two-step mechanism that takes into account the delay in the interaction, and the mechanism of compound-nucleus formation.

A study of the (α, t) reaction on 19F, 27Al, 51V and 59Co

Abstract The angular distributions of tritons from the (α, t) reaction on 19 F, 27 Al, 51 V and 59 Co nuclei corresponding to the (0 + ) ground states and (2 + ) excited states in the final nuclei have been measured in the angular range between 15° and 170° at α-particle energies of 25 MeV. For reactions on 27 Al and 51 V nuclei, the differential excitation functions have also been obtained at different angles of outgoing tritons at E α from 20 to 25 MeV. The experimental angular distributions are analysed by the DWBA approximation on the assumption of a nucleon stripping mechanism. The analyses of the present results and the data obtained earlier for the ( α , t) reaction on the 1 p shell nuclei, A ≲ 30, reveal that the distinguishing feature of the reaction under study is the presence of backward angle peaks in the reaction cross section, which appear to be associated with exchange processes. For the ( α , t) reaction on the heavier nuclei ( A > 30), the dominant mechanism is nucleon stripping.

Angular correlations in the inelastic-scattering process 24Mg(d, dγ)24Mg at Ed = 15.3 MeV

The double-differential cross sections for the reaction 24Mg(d, dγ1.369)24Mg at the projectiledeuteron energy of Ed = 15.3 MeV weremeasured for deuteron emission angles in the forward hemisphere. All even spin-tensor components of the density matrix for the 2+ state of the 24Mg nucleus at 1.369 MeV were reconstructed, and its orientation properties were determined. These experimental results were compared with the results of calculations based on various versions of the coupled-channel method.

Using a 120-cm cyclotron to study the synchronous effects of ionizing radiation and hypomagnetic conditions on the simplest biological objects

The effect of α-particles on one of the simplest unicellular organisms, Synechocystis sp. PCC 6803 cyanobacteria, is studied using a 120-cm cyclotron. Suspensions of cells are irradiated in a cuvette with walls made of thin mylar films. The energy of α-particles in the solution is 24 MeV. The linear energy transfer (LET) of α-particles is close to that of relativistic nuclei of the neon-magnesium group in galactic cosmic rays, making it possible to simulate their effect on biological objects. A number of apparent changes in the Synechocystis spectral characteristics are found for samples irradiated in and outside a hypomagnetic field.

Populations of sublevels 24Mg(2+) nucleus formed in the reaction 24Mg(d, d1γ)24Mg at Ed = 15.3 MeV

Angular dependences of density matrix spin tensors and sublevel populations are experimentally reconstructed for the 24Mg(2+, 1.369 MeV) nucleus formed in the inelastic scattering of deuterons by 24Mg at Ed = 15.3 MeV and deuteron emission angles from 25° to 165° (lab). The experimental results are compared to those from calculations using different versions of the coupled-channel method.

Using the U-120 cyclotron to study the effect of 30 MeV alpha particles on a liposome membrane

We studied the effect of α particles with energies 30.5 MeV, emitted from the 120-cm cyclotron at Skobeltsyn Research Institute of Nuclear Physics, MSU, on artificial membrane systems (liposomes) to simulate the effects of ionizing galactic cosmic rays on biological subjects. The start of low-level lipid peroxidation, accompanied by a change in the ordering of fatty acid residues in a part of the membrane remote from β-carotene molecules, was observed after irradiation by α-particles. The presented method proved to be quite effective and reliable.

Correlation features of the reaction 9Be(d, pγ)10Be at Ed=15.3 MeV and structure of the 10Be nucleus

Double-differential cross sections for the reaction 9Be(d, pγ)10Be at Ed=15.3 MeV are measured for proton emission into the forward hemisphere. All even spin-tensor components of the density matrix for the 2+ 3.37-MeV state of the residual nucleus are reconstructed in a model-independent way. The angular distributions of the populations of the magnetic substates and of the tensors of the angular-momentum orientation for the state in question are also obtained. The experimental results are compared with the results of the calculations performed by the coupled-channel method under the assumption of the neutron-stripping mechanism. The calculated correlation features are found to be highly sensitive to the wave functions for the participant nuclei, especially the 10Be nucleus. The importance of taking into account multistep processes in the reaction being considered is demonstrated.

Investigation of αγ angular correlations in the reaction 15N(p, αγ)12C induced by 7.5-MeV protons

The double-differential cross sections for the reaction 15N(p, αγ)12C induced by 7.5-MeV protons are measured for alpha-particle emission angles from 20° to 160°. All even spin-tensor components of the density matrix for the 2+ state (4.44 MeV) of the final nucleus are reconstructed by a model-independent method. For the same state of the carbon nucleus, the populations of magnetic sublevels and the components of the angular-momentum-orientation tensor are analyzed as functions of the alpha-particle emission angle. Our experimental data are compared with theoretical predictions based on the triton-cluster-pickup mechanism treated within the coupled-channel method. It is shown that correlation features are sensitive to the reaction mechanism and to structural characteristics of the nuclei involved. The role of sequential processes is emphasized.

Determination of Energy of n n-Singlet Virtual State in \(\varvec{d+{{}^{2}}}\hbox {H}\varvec{\rightarrow p+p+n+n}\) Reaction

The nn final state interaction has been investigated in d+2H->(pp)S+(nn)S->p+p+n+n reaction going through a formation and breakup of singlet diproton and dineutron in the intermediate state. In the kinematically complete experiment performed at Ed =15 MeV two proton and neutron were detected at angles close to those of emission of (pp)S and (nn)S systems. Simulation of the reaction showed that the shape of neutron energy (timing) spectrum depends on epsnn - the energy of virtual 1S0 state of nn-system. The most likely value epsnn = 0.076 +/- 0.006 MeV was obtained by fitting procedure using the experimental data and simulations. This low value of epsnn evidently indicates on effective enhancement of nn-interaction in the intermediate state of studied reaction