V. A. Ziman

Structure of Be-12: Intruder d-wave strength at N=8

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the [FORMULA: SEE TEXT]orbital and the [FORMULA: SEE TEXT], intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be.

α-particle production in the scattering of 6He by 208Pb at energies around the Coulomb barrier

New experimental data from the scattering of 6He + 208Pb at energies around and below the Coulomb barrier are presented. The yield of breakup products coming from projectile fragmentation is dominated by a strong group of α particles. The energy and angular distribution of this group have been analyzed and compared with theoretical calculations. This analysis indicates that the α particles emitted at backward angles in this reaction are mainly due to two-neutron transfer to weakly bound states of the final nucleus.

Energy dependence of the 8Be + 13C interaction

Abstract Angular distributions of the 9Be(12C,13C)8Be reaction were measured at the beam energy of Elab(12C) = 65 MeV for the transitions to the ground, 3.09 MeV (1/2+) and 3.68 MeV (3/2−) + 3.85 MeV (5/2+) excited states of the 13C nucleus. These data together with experimental data at the energies of Elab(12C) = 12, 15 MeV and Elab(9Be) = 20 MeV were analyzed within the coupled reaction channels (CRC) model. The elastic and inelastic scattering as well as one- and two-step transfers were included in the coupled channel scheme. It was found that n- and α-transfers dominate in these reactions. The energy dependence of the OM potential for the 8Be + 13C channel was deduced. A good description of all sets of experimental data was achieved.

Energy dependence of the nucleus–nucleus interaction in the 9Be + 12C system and the 9Be reorientation

Abstract The angular distributions of elastic and inelastic scattering of the 12 C ions on the 9 Be nuclei were measured using the Kiev U-240 cyclotron at the beam energy 65 MeV for the transitions to the ground state of the 12 C nucleus and to the ground, 1.68 MeV and 2.43 MeV excited states of the 9 Be nucleus. These data and elastic scattering in the 9 Be + 12 C system in the energy range of E cm =5.14–90.46 MeV were analyzed within the optical and coupled reaction channel (CRC) models. The elastic and inelastic scattering, transfer reactions and spin reorientation of the 9 Be nucleus in the ground state were included in the coupled channel scheme. The data of inelastic scattering at E lab ( 12 C)=65 MeV were used to determine the deformation parameters of 9 Be nucleus in the ground state. It was found that the reorientation process dominates in the elastic scattering data at large angles. A good description of all sets of experimental data was achieved. The energy dependence of parameters for the real and imaginary parts of the optical potential was analyzed using analytic forms of the Woods–Saxon type. The dispersion relation between the real and imaginary parts of the optical potential was applied in the analysis of the energy dependence. The parameters for the energy dependence of the 9 Be + 12 C optical potential were determined.

{alpha}-decaying states {sup 18}O, {sup 20}Ne and {sup 22}Ne in {sup 18}O beam induced reactions

The three reactions {sup 12}C({sup 18}O,{sup 14}C+{alpha}){sup 12}C, {sup 12}C({sup 18}O,{sup 16}O+{alpha}){sup 10}Be, and {sup 12}C({sup 18}O,{sup 18}O+{alpha}){sup 8}Be have been used to investigate {alpha}-decaying states in the nuclei {sup 18}O, {sup 20}Ne, and {sup 22}Ne populated through inelastic scattering, 2p, and {alpha} transfer, respectively. The measurements were performed at a beam energy of 140 MeV, and two charged particle detector telescopes were used to detect the breakup of the projectile-like particle. States in {sup 18}O, {sup 20}Ne, and {sup 22}Ne were observed in the excitation energy range from 7 to 22 MeV and angular correlation techniques were used to determine the spins of a number of these states. The data are interpreted in terms of the underlying cluster structure. In the case of the {sup 18}O, {sup 14}C core + {alpha}, cluster bands, that are the analog of those in {sup 20}Ne have been identified.

Cluster breakup of 18O and 22Ne

The 14C + α breakup of 18O has been studied at energies of Ebeam = 136 MeV and 148.5 MeV, using a 200 µg cm−2 thick Be target. Several states belonging to the proposed octupole deformed band, previously associated with the 8.04 MeV, 1− and 8.22 MeV, 2+ states, have been populated through inelastic excitation. A candidate for the 7− member was not found, providing evidence that the negative parity component of the band terminates at the 5− member. This is shown to be consistent with the Nilsson description of the systematics in the 16O, 18O and 20Ne nuclei. In addition, several states at Ex > 13 MeV in 18O have been measured to α-decay for the first time. The α-transfer reactions 9Be(18O, 12C 10Be)5He, 9Be(18O, 13C 9Be)5He and 9Be(18O, 18O 4He)5He were also measured; however, little or no evidence for the population of states in 22Ne was found.

One- and two-step processes in the 6Li(d,6Li), (d,7Li) and (d,7Be) reactions at Ed = 50 MeV

Abstract The cross sections for the (d, 6 Li), (d, 7 Li) and (d, 7 Be) reactions on the 6 Li nuclei were measured at the deuteron energy of 50 MeV for transitions to the ground state of 6 Li and to the ground and first excited states of 7 Li and 7 Be nuclei. The experimental data were analyzed with the coupled reaction channel model. It was found that both one- and two-step cluster transfers give substantial contributions to the cross sections. Reasonable agreement between measured and calculated cross sections was achieved. The asymmetry in the angular distributions between the (d, 7 Li) and (d, 7 Be) reactions was observed experimentally. We discuss the effects that lead to the charge symmetry violation.

B(E1) Strengths from Coulomb excitation of 11Be

The B(E1;1/2{sup +}{yields} 1/2{sup -}) strength for {sup 11}Be has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for {sup 11}Be+{sup 208}Pb at 38.6 MeV/nucleon is reported. The B(E1) strength of 0.105(12) e{sup 2}fm{sup 2} derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, in contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e{sup 2}fm{sup 2}. This value is in good agreement with the value deduced independently from the lifetime of the 1/2{sup -} state in {sup 11}Be, and has a comparable precision.

One- and two-step mechanisms of the 9Be(12C,11B)10B reaction at Elab(12C)=65 MeV and the energy dependence of 11,10B+10B interactions

Abstract Angular distributions of the 9 Be( 12 C, 11 B) 10 B reaction were measured at the energy of E lab ( 12 C)=65 MeV for transitions to the ground and 0.72 MeV (1 + ), 1.74 MeV (0 + , T =1), 3.59 MeV (2 + ) excited states of the 10 B nucleus and 2.12 MeV (1/2 − )+2.15 MeV (1 + ) excited states of 11 B and 10 B nuclei, respectively. Data were analyzed within the coupled reaction channel (CRC) model including one- and two-step transfer mechanisms. The elastic and inelastic scattering and p-, d-, (d + n)-, (n + p)-, ( 3 He + p)- and ( 3 He + d)-transfer mechanisms were included in the coupled channel scheme. It was found that two-step processes are important for all transitions. Data of 10 B+ 10 B elastic scattering from the literature were included in the analysis of the energy dependence of optical model parameters for 10 B+ 10 B and 10 B+ 11 B interactions. A good description of all sets of experimental data was achieved.

Direct versus exchange processes in the reactions 7Li(14N, 14,15N) at 110 MeV

The angular distributions of elastic and inelastic scattering of the 14N ions by the 7Li nuclei were measured for the transitions to the ground and 3.948 MeV (1+), 4.915 MeV (0−)+5.106 MeV (2−), 6.204 MeV (1+)+6.444 MeV (3+), 7.967 MeV (2−) excited states of the nucleus 14N and to the ground and 4.63 MeV (7/2−), 6.68 MeV (5/2−), 7.467 MeV (5/2−) excited states of the nucleus 7Li at Elab(14N)=110 MeV. The angular distribution of the reaction 7Li(14N, 15N)6Li was obtained simultaneously at the same energy. The experimental data were analyzed within coupled reaction channels (CRC) method. The elastic and inelastic scattering as well as transfers of clusters were included in the coupling scheme. We have concentrated on the study of the reaction mechanism at backward angles where anomalous large-angle scattering (ALAS) is observed. Unlike in many other reactions, the reorientation of 7Li was found to be by far the most dominant mechanism in this region. The deformation parameters for the nuclei of 7Li and 14N were obtained by fitting the experimental data for both elastic and inelastic scattering. The deformation parameters of 7Li obtained from the analysis of elastic and inelastic channels coincide. Good agreement between measured and calculated cross sections was achieved.