[en] A review is presented of the experimental investigations on the stability of very neutron-rich light nuclei carried out at the JINR Laboratory of Nuclear Reactions. Results on mass excess measurements are reported for ⁴H, ⁵H, ⁶H, ⁷H and for the superheavy helium isotope ⁹He. Some results from the joint JINR-Ganil experiment on the search for and study of new neutron-rich light nuclei are also given. Analyzed are new possibilities for the investigation of multineutron decay of light nuclei. 14 refs.; 10 figs

[en] The international school-seminar on heavy ion physics had been organized in Dubna in may of 1993. The scientific program of reports covers the following main topics: synthesis and properties of heavy nuclei; synthesis and investigation of properties of exotic nuclei; experiments with radioactive nuclear beams; interaction between complex nuclei at low and intermediate energies. It also includes reports on laser spectroscopy and exotic nuclear beams, on some application of heavy ion beams for the problems of solid state physics, on construction of multidetector facilities and on developing of heavy ion accelerator complexes. Short communication

[en] A short review is given of the status of investigation of the heavy hydrogen isotopes ^4,5,6H and the multineutron systems consisting of three and four neutrons. The available data are rather controversial. Experiments are suggested for their further study. Also the latest results from the experimental attempt to determine the particle stability of nuclei close to the neutron shells N=20 and N=28 are presented. In this region, known as 'island of inversion', there is evidence of the changing of the magic numbers for very neutron-rich nuclei and their influence on their stability

[en] The scattering of a ⁶Li beam on a ¹²C-target has been studied at (63±0.5) MeV. The reaction products were analyzed by the magnetic spectrometer MSP-144 and identified with a focal plane detector by their energy loss and residual energy in a gas-filled ionization chamber. The position in the focal plane was determined using proportional counters by the charge-division technique. The elastic scattering was measured for the angular range from 10 to 95 deg c.m. with Δθ = ± 0.5 deg. The inelastic scattering data were taken for exciting the 2⁺ (4.44 MeV) state in ¹²C. The calculations of the angular distributions of elastically and inelastically scattered ⁶Li nuclei have been carried out within the optical model and by the method of DWBA, respectively. A parametrization is proposed for the optical potential of the interaction of ⁶Li nuclei of different energies with a broad range of target masses. The calculated differential cross sections of elastic and inelastic scattering demonstrate good agreement with the available experimental data. The possibility of future experiments using radioactive beams at DRIBs is also discussed. (author)

[en] Energy spectra have been measured for α-particles emitted in the bombardment of ¹⁵⁹Tb, ¹⁸¹Ta, ¹⁹⁷Au, and ²³²Th nuclei by ²⁰Ne, ²²Ne, and ⁴⁰Ar projectiles. The reaction products emitted in the angular range (0+-2)deg relative to the beam direction were analyzed using a magnetic spectrometer and detected by means of a semiconductor ΔE-E telescope. It was found that in all cases the experimentally measured maximum α-particle energy almost amounts to the maximum possible value calculated from the reaction energy balance for a two-body exit channel. A correlation was found between the measured absolute cross section in different target-projectile combinations and the α-particle binding energy in the target nuclei. On the basis of the obtained results a conclusion has been drawn that the α-particles are emitted in the early stage of the reaction

[en] Proceedings of the fifth school-seminar on heavy ion physics are given. Special attention is paid to reaction mechanism at low, medium and high energies. The problems on experiments carrying out and experimental development of nuclear beam facilities are discussed

[en] The possibilities of the CR-39 plastic for the detection and identification of the He, Li, Be, and B isotopes produced in heavy ion reactions were studied using a magnetic spectrometer placed at 0 deg with respect to the beam. The products of the reaction sup(nat)Ti+sUp(22)Ne (178 MeV) were incident on the CR-39 detector at an angle of 90 deg. Their identification was performed by track diame-ter determination as a function of energy and specific ionization. The presented results coincide within 10% with those obtained using a semiconductor ΔE-E telescope of the same geometry. Thus CR-39 plastic detector has proved to have good spectroscopic properties which make it useful for heavy ion reaction studies

[en] Lifetimes of high-spin levels of the main rotational band of ¹⁶⁶Yb were measured. The ¹⁶⁶Yb nuclei were obtained by the reaction ¹³⁰Te (⁴⁰Ar, 4n) ¹⁶⁶Yb. The enriched (95%) ¹³⁰Te target (thickness 1.2 mg/cm²) was irradiated with 168 MeV ⁴⁰Ar ion beam. Lifetimes were measured by the gamma Doppler shift caused by ¹⁶⁶Yb recoil in vacuum. The excited recoil nuclei were stopped in Bi. The bismuth-target distance D was varied. The ratio y of the unshifted γ-peak (decay after being stopped) to the total gamma intensity was measured, the decay curves of the levels were calculated. The accuracy of relative distance measurements is +- 0.5 μm. Lifetimes of the high-spin rotational levels of ¹⁶⁶Yb with Isup(π) from 10⁺ to 16⁺ were obtained, also of Isup(π) = 2⁺, 4⁺, 6⁺, 8⁺ levels. The experimental values were compared with the predictions of the rigid rotator model, no serious descrepancies being observed. The main parameters characterizing the rotational bands of the ground state of even-even Yb isotopes (M=160, 162, 164, 166) are compared. All parameters (moment of inertia, inner quadrupole moment, quadrupole deformation parameter of the nucleus) decrease continuously with decreasing mass number M. Furtheron, the probability and the time of independent occupation of the high-spin levels of the compound nucleus were measured

[en] Proceedings of the fifth school-seminar on heavy ion physics are given. Special attention is paid to heavy ion reactions and nuclear fission. The problems on nuclear spectroscopy of heavy ions are considered in detail

[en] Experimental results of measuring mass distribution of compound nucleus fission fragments, produced in the ²⁰⁸Pb+⁴⁸Ca reaction at 25 MeV excitation energy are presented. The radiochemical technique was used in the experiments. Mass and isotopic distributions of ²⁵⁶102 compound nucleus fission fragments have been obtained. Mass distributions had sharply expressed asymmetry, in this case asymmetrical fission with heavy fragment generation in the mass region Asub(N)=142-145 1.5-1.7 times more preferable than asymmetric distribution Asub(N)=Asub(L) approximately 128. The asymmetric mass distribution obtained testifies to the shell effects conservation in the ²⁵⁶102 nucleus at 25 MeV excitation energy