Yu. E. Penionzhkevich

Electric and nuclear transition strength in 30,32Mg

Abstract The charge and mass transition matrix elements of the neutron-rich isotopes 30,32 Mg have been extracted from inelastic scattering on 208 Pb and 12 C targets at 32xa0 A xa0MeV. The measured inelastic cross sections for the first 2 + states were compared to coupled-channels calculations, which take into account the feeding from higher excited states. The method was tested with 24 Mg inelastic scattering data obtained in the same experiment. In the framework of the rotational model, the charge and mass deformations are identical and large (| β |∼0.5–0.6) for both isotopes.

THE MODIFIED MINI-FOBOS SETUP

The 4π spectrometer FOBOS was proved to be a high-efficiency tool for investigation of the characteristics of multi-body decays of hot heavy nuclei produced in nuclear reactions induced by heavy ions. The time-offlight measurements of charged fragments employing the radio-frequency (RF) signal of the cyclotron U400-M to deduce the START signal require no special START detectors and, hence, the big fraction of the total solid angle is available for particle detection. The lack of the RF signal in experiments aimed at search for the exotic decay modes in spontaneous fission enforces to use an additional START detector. The complicated target station equipped by a START detector shadows a large portion of detector modules making thus no sense to use the whole powerful detection system in such experiments. Therefore, it has been decided to build a simplified facility consisting of several standard FOBOS modules only. The miniFOBOS setup, a prototype of the FOBOS spectrometer, has been chosen for that purpose. It was exploited mainly to solve various method tasks related to the construction of the FOBOS spectrometer. The general idea of the modified miniFOBOS setup (MMF) consists in using a small reaction chamber which can be then unique for each experiment and the basic universal system maintaining the detectors. The special mounting cones are used to joint detectors with the reaction chamber (Fig. 1, 2). Such cones can be used, in particular, to build the high efficiency system joining six modules in the form of 3Dcross.

NUCLEAR STRUCTURE STUDIES OF EXOTIC NUCLEI VIA THE STRENGTH OF E2 TRANSITIONS; ADVANCED TIME-DELAYED γγ SPECTROSCOPY AT THE EXTREME

Nuclear structure studies of exotic nuclei via the strength of E2 transitions; advanced time-delayed γγ spectroscopy at the extreme

Energy Dependence of Total Cross Sections for Reactions with 4, 6he, 6, 7, 9li Nuclei

The paper presents the results of measurement of the total cross sections for reactions 4,6He + Si and 6,7,9Li + Si in the beam energy range 5−50 A⋅MeV. The enhancements of the total cross sections for reaction 6He + Si compared with reaction 4He + Si, and 9Li + Si compared with reactions 6,7Li + Si have been observed. The performed microscopic analysis of total cross sections for reactions 6He + Si and 9Li + Si based on numerical solution of the time-dependent Schrodinger equation for external neutrons of projectile nuclei 6He and 9Li yielded good agreement with experimental data.

Role of external neutrons of weakly bound nuclei in reactions with their participation

The paper presents the results of measurement of the total cross sections for reactions 4,6He+Si and 6,7,9Li+Si in the beam energy range 5–50 A MeV. The enhancements of the total cross sections for reaction 6He+Si compared with reaction 4He+Si and 9Li+Si compared with reactions 6,7Li+Si have been observed. The performed microscopic analysis of total cross sections for reactions 6He+Si and 9Li+Si based on numerical solution of the time-dependent Schrodinger equation for external neutrons of projectile nuclei 6He and 9Li yielded good agreement with experimental data.

Some Evidence of the Cluster Struture Inside of 9Be

Angular distributions of protons, deuterons, tritons and alpha-particles emitted from the reactions in the H+Be-system at Elab=19.5 MeV were measured with an aim to shed light on the internal cluster structure of Be and the study of possible cluster transfer of He. The analyses suggest a significant contribution of five-nucleon transfer in the reaction channel Be(d,He)Li.

A NEW SET-UP FOR TOTAL REACTION CROSS SECTION MEASURING

The experimental method and set-up based on 4uf050 n-γ-technique for direct and modelindependent measuring of the total reaction cross section σR have been presented. The excitation function σR(E) for 6 He+ 197 Au reaction at the Coulomb barrier energy region has been measured. The measured data are compared with the summarized cross section which has been prepared by summing of measured cross sections of main reaction channels: 1ntransfer and 197 Au( 6 He, xn)Tl with x = 2÷7 evaporation reaction channels.

DILUTE NUCLEAR STATES IN 12C AND NEIGHBOR NUCLEI

A review of recent experiment including those performed by our collaboration is given. The main accent is done to unique information which is extracted from the measurements of the inelastic scattering cross-sections using the Modified diffraction model (MDM). The enhancement of the radii of some highly excited cluster states of 12 C, 11 B and 13 C was definitely observed. The radii values are in general 20 -30% larger than those of the corresponding ground states but much less than those predicted by the model of alpha particle condensation. A rotational band based on the 0 + 2 (Hoyle) state in 12 C is identified.

The 2n‐Evaporation Channels In the Fusion of 4,6He with 206,208Pb

Excitation functions of the reaction products were measured for the reactions induced by 4,6He projectiles on 206,208Pb targets, leading to the same compound nucleus. This was accomplished by using the stacked‐foil‐activation technique. The identification of the reaction products (accumulated in the Pb targets) was done by their radioactive alp ha decays. The excitation functions for the 2n evaporation channels were obtained at energies below the sub‐Coulomb barrier region. A large value of the fusion cross section was observed in the case of the reaction induced by the weakly bound 6He projectile.

Excitation Functions for Complete Fusion and Transfer Reactions in the Interaction of 4He Nuclei with 197Au

Excitation functions have been measured for the fusion reaction 197Au(αxn)201−xnTl with the evaporation of x neutrons (0⩽x⩽3) in the energy range 14–36 MeV. The induced‐activation method was used for registration and identification of the reaction products. The experimental cross sections for the (1–3)‐neutron evaporation residues are in good agreement with the results known from literature. For the radiation capture reaction 197Au(α,γ)201Tl, the upper limit was obtained essentially lower. The excitation functions for the measured reactions are compared with calculations in the frame of the statistical model, as well as with formerly measured similar data with a 6He beam.