Fine and hyperfine structure of the muonic <Superscript>3</Superscript>He ion

On the basis of quasipotential approach to the bound state problem in QED we calculate the vacuum polarization, relativistic, recoil, structure corrections of orders α ⁵ and α ⁶ to the fine structure interval ΔE ^fs = E(2P _3/2) − E(2P _1/2) and to the hyperfine structure of the energy levels 2P _1/2 and 2P _3/2 in muonic ₂³He ion. The resulting values ΔE ^fs = 144 803.15 μeV, Δ$ \tilde E $ \tilde E ^hfs(2P _1/2) = −58 712.90 μeV, Δ$ \tilde E $ \tilde E ^hfs(2P _3/2) = −24 290.69 μeV provide reliable guidelines in performing a comparison with the relevant experimental data.     

Fine structure of the muonic <Superscript>4</Superscript>He ion

On the basis of quasi-potential approach to the bound state problem in QED we calculate the vacuum polarization, recoil and structure corrections of orders α⁵ and α⁶ to the fine splitting interval ΔE ^fs = E(2P _3/2) − E(2P _1/2) in muonic ₂⁴He ion. The resulting value ΔE ^fs = 146180.68 μeV provides reliable guideline in performing a comparison with the relevant experimental data.     

Different formulations of <Superscript>3</Superscript>He and <Superscript>3</Superscript>H photodisintegration

Different momentum space Faddeev-like equations and their solutions for the radiative pd-capture and the three-nucleon photodisintegration of ³He are presented. Applications are based on the AV18 nucleon-nucleon and the Urbana IX three-nucleon forces. Meson exchange currents are included using the Siegert theorem. A very good agreement has been found in all cases indicating the reliability of the used numerical methods. Predictions for cross-sections and polarization observables in the pd-capture and the complete three-nucleon breakup of ³He at different incoming-deuteron/photon energies are presented.     

Recent results on hyperpolarized<Superscript>3</Superscript>He−<Superscript>4</Superscript>He liquid mixtures

Laser optical pumping in low magnetic field provides very high nuclear polarizations in gaseous helium mixtures, and is used to prepare polarized liquid. Wall relaxation in glass cells is effiently reduced using cesium coatings, and bulk longitudinal relaxation times are measured. In highly magnetized samples, dipolar fields control the spin dynamics in anisotropic volumes and weak external magnetic field inhomogeneities. Long lived magnetostatic modes are observed by pulsed NMR. Detailed analysis of their frequency and damping gives information on magnetization density and spin diffusion coefficient in polarized mixtures. Experiments are performed above 0.2 K on mixtures with³He concentrations of order a few percents or larger. When phase separation occurs, the³He-rich phase retains a high polarization.     

Kinetics of the sorption of <Superscript>3</Superscript>He by C<Subscript>60</Subscript> fullerite. The quantum diffusion of <Superscript>3</Superscript>He and <Superscript>4</Superscript>He in fullerite

The kinetics of the sorption and subsequent desorption of gaseous ³He in a C₆₀ fullerite powder has been studied in the temperature range of 2–292 K. The temperature dependences of the diffusion coefficients of ³He and ⁴He impurities in fullerite have been plotted using the measured characteristic times of filling of octahedral and tetrahedral interstices, as well as previous data. These temperature dependences of the diffusion coefficients of ³He and ⁴He impurities in fullerite are qualitatively similar. A decrease in the temperature from 292 to 79 K is accompanied by a decrease in the diffusion coefficients, which corresponds to the dominance of the thermally activated diffusion of helium isotopes in fullerite. A further decrease in the temperature to 8–10 K leads to an increase in the diffusion coefficients by more than an order of magnitude. The diffusion coefficients of ³He and ⁴He are independent of the temperature below 8 K, indicating the tunnel character of the diffusion of helium in C₆₀ fullerite. The isotope effect is manifested in the difference between the absolute values of the diffusion coefficients of ³He and ⁴He atoms at the same temperatures.     

Applications of <Superscript>3</Superscript>He neutron detectors

Neutron detectors with ³He-filled proportional counters are described. The use of these detectors in measuring the probability of neutron emission (in particular, multiparticle neutron emission) after the β decay of neutron-rich nuclei and in studying rare events of spontaneous fission of superheavy nuclei is considered.     

Appearance of anomalous phase in <Superscript>4</Superscript>He crystal in the presence of small <Superscript>3</Superscript>He impurity

The kinetics of formation of an anomalous phase from a solution with a small ³He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ～30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface.     

Decay of the anomalous state of a <Superscript>4</Superscript>He crystal

The relaxation of the anomalous state, i.e., the return of the growth kinetics to the regime typical of crystals in the normal state, is studied experimentally in the temperature range 0.48–0.68 K. It is found that the relaxation process with the growth rate decreasing by two orders of magnitude mainly occurs 1–20 ms after the termination of the fast growth stage. Slow relaxation to the normal values of the kinetic growth coefficient is observed subsequently during a time interval equal approximately to 100 ms.     

Pionic atom spectroscopy in the (d,<Superscript>3</Superscript> He) reaction at finite angles

We study the formation of deeply bound pionic atoms in the (d, ³He) reactions theoretically and show the energy spectra of the emitted ³He at finite angles, which are expected to be observed experimentally. We find that the different combinations of the pion-bound and neutron-hole states dominate the spectra at different scattering angles because of the matching condition of the reaction. We conclude that the observation of the (d, ³He) reaction at finite angles will provide the systematic information of the pionic bound states in each nucleus and will help to develop the study of the pion properties and the partial restoration of chiral symmetry in nuclei.     

Momentum distributions of <Superscript>4</Superscript>He nuclei from the <Superscript>6</Superscript>He and <Superscript>6</Superscript>Li breakup

Experimental data on the momentum distributions of ⁴He nuclei originating from ⁶He and ⁶Li breakup on various targets are presented over a wide beam energy range. The experiment with ⁶He was performed at the DRIBs accelerator complex for radioactive beams at the Joint Institute for Nuclear Research (JINR, Dubna). The intensity of the ⁶He beam used was 5 × 10⁶ particles per second and its energy was 10 MeV per nucleon. The momentum distributions of breakup products were measured by means of the MSP-144 magnetic spectrometer. The distribution width was shown to be virtually independent of the target mass. A small value of this width, σ ～ 28 MeV/c, confirms the presence of a halo in ⁶He. The measurements performed with ⁶Li beams of energy 18 and 46 MeV per nucleon at the U-400M accelerator yielded a width value of σ ～ 50 MeV/c for the momentum distributions of ⁴He nuclei, which is intermediate between that for ⁶He and those for stable nuclei. A compilation of the widths of the momentum distributions of fragments originating from the breakup of various nuclei is presented versus the binding energy of one or two neutrons in these nuclei, the target mass and the projectile energy.     

Phase shift analysis of the <Superscript>6</Superscript>He+<Superscript>208</Superscript>Pb and the <Superscript>6</Superscript>He+<Superscript>197</Superscript>Au systems

We present the elastic scattering of the ⁶He+²⁰⁸Pb and the ⁶He+¹⁹⁷Au systems at the laboratory energy of E _lab=27 MeV within the framework of the McIntyre parametrization, and systematically investigate χ ²/N analysis of both systems to obtain an excellent agreement between the theoretical results and the experimental data. We find large diffusivity parameters indicating long range absorption mechanisms. We also show that both systems lack both the nuclear and the Coulomb rainbow scattering for obtained S-matrix parameters.     

Solar Modulation of <Superscript>2</Superscript>H/<Superscript>1</Superscript>H and <Superscript>3</Superscript>He/<Superscript>4</Superscript>He according to Data Obtained in the PAMELA Satellite-Borne Experiment between 2006 and 2014

Preliminary results of measurements of the solar modulation of the isotopic hydrogen and helium content in galactic cosmic rays are presented for the first time. These data were obtained between 2006 and 2014 in the PAMELA international orbital experiment via measuring the time of flight of nuclei in the Pamela scintillation telescope and via analyzing, in the multilayered calorimeter of the PAMELA magnetic spectrometer, ionization losses of nuclei whose rigidity was known from trajectory measurements and which traversed the instrument without undergoing nuclear interactions. The results of these measurements are compared with existing experimental and calculated data, which are quite scanty.     

<Superscript>6</Superscript>He + <Superscript>6</Superscript>He Clustering of <Superscript>12</Superscript>Be in a Microscopic Algebraic Approach

The norm kernel of the A=12 system composed of two ⁶He clusters, and the L=0 basis functions (in the SU(3) and angular momentum-coupled schemes) are analytically obtained in the Fock-Bargmann space. The norm kernel has a diagonal form in the former basis, but the asymptotic conditions are naturally defined in the latter one. The system is a good illustration for the method of projection of the norm kernel to the basis functions in the presence of SU(3) degeneracy that was proposed by the authors. The coupled-channel problem is considered in the algebraic version of the resonating-group method, with the multiple decay thresholds being properly accounted for. The structure of the ground state of ¹²Be obtained in the approximation of zero-range nuclear force is compared with the shell-model predictions. In the continuum part of the spectrum, the S-matrix is constructed, the asymptotic normalization coefficients are deduced and their energy dependence is analyzed.     

Magnetic properties of <Superscript>3</Superscript>He on the recursive lattices

We considered the Heisenberg model on the recursive lattices with multi-spin interaction in a strong magnetic field as an approximation of the two-dimensional kagome lattice, as well as hexagonal recursive lattices as an approximation of triangular lattice, for solid ³He. In a strong magnetic field it is possible to approximate the Heisenberg model with the Izing one. Using dynamic approach, we obtain exact recursion relations for partition functions. Diagrams of the magnetization versus external magnetic field with different spin-exchange parameters and temperatures are presented. Magnetization plateaux, bifurcation points, and doublings are obtained.