N. Soić

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.

4 He Decay of Excited States in 14 C

A study of the 7Li(9Be,4He 10Be)2H reaction at E{beam}=70 MeV has been performed using resonant particle spectroscopy techniques and provides the first measurements of alpha-decaying states in 14C. Excited states are observed at 14.7, 15.5, 16.4, 18.5, 19.8, 20.6, 21.4, 22.4 and 24.0 MeV. The experimental technique was able to resolve decays to the various particle bound states in 10Be, and provides evidence for the preferential decay of the high energy excited states into states in 10Be at ~6 MeV. The decay processes are used to indicate the possible cluster structure of the 14C excited states.

3D hydrogen profiling using a proton microbeam

Abstract A new method for 3D hydrogen profiling is introduced. The method is based on the proton-proton coincidence measurement and uses a standard microbeam facility. The 3D profile is derived from depth profiles at a set of points combined with the average hydrogen areal density of the sample. The deconvolution technique, in which the depth profiles are described as a sum of cubic splines, is applied. The average hydrogen areal density is determined by a scanning proton microbeam. Samples of a known hydrogen distribution were used to test the method.

{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.

First Measurement of the 19F(α, p)22Ne Reaction at Energies of Astrophysical Relevance

The observational 19F abundance in stellar environments systematically exceeds the predicted one, thus representing one of the unsolved challenges for stellar modeling. It is therefore clear that further investigation is needed in this field. In this work, we focus our attention on the measurement of the 19F(α, p) 22Ne reaction in the astrophysical energy range, between 0.2 and 0.8 MeV (far below the Coulomb barrier, 3.8 MeV), as it represents the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct measurements is ∼0.66 MeV, covering only the upper tail of the Gamow window, causing the reaction-rate evaluation to be based on extrapolation. To investigate lower energies, the 19F(α, p) 22Ne reaction has been studied by means of the Trojan horse method, applied to the quasi-free 6Li (19F, p22Ne)2H reaction at Ebeam = 6 MeV. The indirect cross section of the 19F(α, p) 22Ne reaction at energies ≲1 MeV was extracted, fully covering the astrophysical region of interest and overlapping existing direct data for normalization. Several resonances have been detected for the first time inside the Gamow window. The reaction rate has been calculated, showing an increase up to a factor of 4 with respect to the literature at astrophysical temperatures. This might lead to potential major astrophysical implications.

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.

8Li + α decay of 12B and its possible astrophysical implications

The 12B excitation energy spectrum has been obtained from coincidence measurements of the 9Be + 7Li → 2α + 8Li reaction at E0 = 52 MeV. The decay of the states at excitations between 10 and 16 Mev into α + 8Li has been observed for the first time. Observed α-decay indicates possible cluster structure of the 12B excited states. The influence of these states on the cross-section of the astrophysically important 8Li(α,n)11B and 9Be + t reactions is discussed and the results are compared with existing results.

4He1H2+ and 4He2H+, exotic impurities in 6He+ beam

(HeH2+)-He-4-H-1 ions were observed as an impurity in a 17.0 MeV He-6(+) beam produced by CYCLONE, with the ratio of Intensities being 1:5400. A (HeH+)-He-4-H-2 beam was also observed, having 60 times weaker intensity and slightly lower magnetic rigidity than original He-6(+) beam

α-5He decaying states and the ground-state rotational band of 9Be

In a measurement of the 9Be(7Li, 7Liα)αn reaction at Ei = 52 MeV it is unambigously established for the first time that the 9Be excited states around 6.5 and 11.3 MeV decay into the α + 5He channel. This fact may support previous claims that the 11.3 MeV state is also a member of the ground-state rotational band.

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.