The reduced transition probabilities $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+},{2}_{2}^{+})$ in $^{70}\mathrm{Zn}$ and the full $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}^{+})$ strength up to ${\mathrm{S}}_{n}=7.79\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$ in $^{68}\mathrm{Ni}$ have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a $^{208}\mathrm{Pb}$ target. The $\ensuremath{\gamma}$ rays emitted in-flight were detected with an array of $46{\mathrm{BaF}}_{2}$ crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the ${2}^{+}$ states. The measured $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ of 1432(124) ${e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{4}$ for $^{70}\mathrm{Zn}$ falls in the lower part of the published values which clustered either around 1600 or above $2000\phantom{\rule{3.33333pt}{0ex}}{e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{4}$, while the $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{2}^{+})$ of 53(7) ${e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{4}$ agrees very well with the two published values. The relatively low $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ of 301(38) ${e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{4}$ for $^{68}\mathrm{Ni}$ agrees with previous studies and confirms a local magicity at $Z=28$, $N=40$. Combining the results of the low-energy spectra of $^{68}\mathrm{Ni}$ and $^{70}\mathrm{Zn}$ and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed $E2$ strength of only about $150\phantom{\rule{4pt}{0ex}}{e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{4}$ has been found experimentally at high excitation energy, likely due to proton excitations across the $Z=28$ gap. The experimental distribution of this high-energy $E2$ excitation agrees with shell-model calculations, but its strength is about two times weaker.

Background: The influence of halo structure of He-6, B-8, Be-11, and Li-11 nuclei in several mechanisms such as direct reactions and fusion is already established, although not completely understood. The influence of the C-10 Brunnian structure is less known. Purpose: To investigate the influence of the cluster configuration of C-10 on the elastic scattering at an energy close to the Coulomb barrier. Methods: We present experimental data for the elastic scattering of the C-10 + Pb-208 system at E-lab = 66 MeV. The data are compared to the three- and the four-body continuum-discretized coupled-channels calculations assuming B-9 +p, Be-6 +alpha, and Be-8 +p + p configurations. Results: The experimental angular distribution of the cross sections shows the suppression of the Fresnel peak that is reasonably well reproduced by the continuum-discretized coupled-channels calculations. However, the calculations underestimate the cross sections at backward angles. Couplings to continuum states represent a small effect. Conclusions: The cluster configurations of C-10 assumed in the present work are able to describe some of the features of the data. To explain the data at backward angles, experimental data for the breakup and an extension of theoretical formalism towards a four-body cluster seem to be in need to reproduce the measured angular distribution.

The reduced transition probabilities B(E2; 0(g.s.)(+) -> 2(1)(+), 2(2)(+)) in (70) Zn and the full B(E2; 0(g.s.)(+) -> 2(+)) strength up to S-n = 7.79 MeV in Ni-68 have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a Pb-208 target. The gamma rays emitted in-flight were detected with an array of 46BaF(2) crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the 2(+) states. The measured B(E2; 0(g.s.)(+) -> 2(1)(+)) of 1432(124) e(2) fm(4) for Zn-70 falls in the lower part of the published values which clustered either around 1600 or above 2000 e(2) fm(4), while the B(E2; 0(g.s.)(+) -> 2(1)(+)) of 53(7) e(2) fm(4) agrees very well with the two published values. The relatively low B(E2; 0(g.s.)(+) -> 2(1)(+)) of 301(38) e(2) fm(4) for Ni-68 agrees with previous studies and confirms a local magicity at Z = 28, N = 40. Combining the results of the low-energy spectra of Ni-68 and Zn-70 and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate, and triaxial) are present. Finally, a summed E2 strength of only about 150 e(2) fm(4) has been found experimentally at high excitation energy, likely due to proton excitations across the Z = 28 gap. The experimental distribution of this high-energy E2 excitation agrees with shell-model calculations, but its strength is about two times weaker.

Direct measurements of the total fusion cross section for B8+40Ar were achieved with the active target technique. The fusion excitation function was extracted at energies near the Coulomb barrier. The cross section is well described by a coupled reaction channels calculation. The data were compared with previous B8 fusion experiments on Si28 and Ni58 targets. No evidence of striking enhancement of the total fusion cross section at near the Coulomb barrier, that was previously reported for the B8+58Ni system, was observed in these direct measurements. The present data are systematically consistent with the results for B8+28Si at higher energies and with other weakly-bound systems at near-barrier energies.

The TETRA long neutron counter is operated at ALTO ISOL facility behind the PARRNe mass separator. TETRA has been proven to be a unique instrument for measurements of beta-decay properties of short-lived neutron-rich nuclei having applications for the nuclear structure and/or astrophysical r-process calculations. A proper calibration of TETRA can allow validation of the experimental procedure used for determination of beta-delayed one-neutron emission probabilities (P-1n). It requires the use of a well-known beta-neutron decaying radioactive source which can be only produced and measured on-line due to its short half-life. Thus, the present paper reports on measurements of P-1n and T(1/2 )of Rb-96,Rb-97 nuclei using TETRA. The results obtained are in a good agreement with the values available in the literature. This proves that the developed techniques can be applied to unknown P-1n and T-1/2 of neutron-rich species.

In the past several years, there has been a large interest of Time Projection Chambers (TPCs) for use in experimental nuclear physics. This has continued in tandem with the requirement for high efficiency detectors with low intensity radioactive ion beams. TexAT is a Active Target TPC (AT-TPC) built at Texas A&M University utilizing MICRO MEsh GASeous (MicroMegas) pads and GET electronics developed specifically for TPCs. This design combines good TPC pixelation with a surrounding shell of Si/CsI telescopes to make an extremely versatile detector capable of a wide range of different experimental techniques with only minor modifications to the electronics setup. Two recent experiments performed at the Cyclotron Institute, Texas A&M University, are detailed here demonstrating versatility beyond the usual Thick Target Inverse Kinematics (TTIK) or transfer reactions that these TPCs are more typically used for. The first, a measurement of the 12N → 12C* → 3α decay demonstrates the capabilities of TexAT as a low-energy detector operating at low pressure (20 Torr) to measure β-delayed particle decay. The second, a direct measurement of the 8B+40Ar fusion cross section shows the advantages of operating in active target mode where the target also functions as the detector gas.

The reduced transition probabilities B(E2; 0 + g.s.→ 2 + 1 ) of the 46 Ar and 44 Ca nuclei were studied using the Coulomb excitation technique at intermediate energy at the LISE/GANIL facility.The in-flight γ rays, emitted after the Coulomb excitation of their first 2 + states, were detected in an array of 64 BaF 2 crystals.The present B(E2 ↑) value for 44 Ca, 475(36) e 2 fm 4 , agrees well with the value of 495(35) e 2 fm 4 obtained by averaging results of previous experiments.Consistent B(E2; 0 + g.s.→ 2 + 1 ) values of 225(29) e 2 fm 4 and 234(19) e 2 fm 4 have been obtained for 46 Ar from an absolute and a relative measurement, normalized to the 44 Ca value.Both results agree with the ones obtained with the same experimental technique at the NSCL facility but are a factor of 2 smaller than the shell model predictions.The drop in B(E2; 0 + g.s.→ 2 + 1 ) in the Ar chain at N = 28, confirmed in this experiment, shows that 46 Ar is sensitive to the N = 28 shell closure.

The Isoscalar Giant Monopole Resonance (ISGMR) and the Isoscalar Giant Dipole Resonance (ISGDR) compression modes have been studied in the doubly-magic unstable nucleus 56Ni. They were measured by inelastic α-particle scattering in inverse kinematics at 50 MeV/u with the MAYA active target at the GANIL facility. The centroid of the ISGMR has been obtained at Ex=19.1±0.5 MeV. Evidence for the low-lying part of the ISGDR has been found at Ex=17.4±0.7 MeV. The strength distribution for the dipole mode shows similarity with the prediction from the Hartree–Fock (HF) based random-phase approximation (RPA) [1]. These measurements confirm inelastic α-particle scattering as a suitable probe for exciting the ISGMR and the ISGDR modes in radioactive isotopes in inverse kinematics.

A. S. Denikin a, b, , S. M. Lukyanov , N. K. Skobelev , Yu.G. Sobolev , E. I. Voskoboynik , Yu. E. Penionzhkevich b, , W. H. Trzaska , G. P. Tyurin , V. Burjan , V. Kroha , J. Mr azek , S. Pisko r , V. Glagolev , Yi Xu , S. V. Khlebnikov f , M.N. Harakeh , K. A. Kuterbekov h, , Yu. Tuleushev i a International University ©Dubnaa, Dubna, Russia b Joint Institute for Nuclear Research, Dubna c National Research Nuclear University MEPhI, Moscow d Department of Physics, University of Jyvéaskyléa, Jyvéaskyléa, Finland e Nuclear Physics Institute, Re z, Czech Republic f Khlopin Institute, St. Petersburg, Russia g Kernfysisch Versneller Instituut, University of Groningen, Groningen, Netherlands h Eurasian Gumilev University, Astana i Nuclear Physics Institute, Almaty, Kazakhstan

It is well known that the nuclear shell structure changes for the most exotic nuclei. One of the consequences of this phenomenon is the modification of the "classical" magic numbers, as experimentally observed at N = 20 and N = 28. Nevertheless, the mechanisms responsible for such changes are still under discussion and more experimental information is needed to better constrain the theoretical models. In these proceedings, we report on the discovery and the experimental study by precise spectroscopy experiments of the 02+ state in 34Si and 44S⁠. The 34Si is located between the magic spherical 36S and the deformed 32Mg⁠, member of the so-called island of inversion, whereas 44S is located between the magic spherical 48Ca and the deformed 42Si⁠. Therefore, the structure of these nuclei, and in particular the phenomenon of shape coexistence, is of crucial importance to understand how the intruder configurations progressively dominate the ground state structure of the most exotic nuclei at both N = 20 and N = 28.

The preliminary value of the reduced transition probability B(E2; 0(+) -> 2(1)(+)) in Ar-46 has been determined using the Coulomb excitation technique at intermediate energy. The Ar-46 was produced in the fragmentation of a Ca-48 beam at GANIL. The gamma-rays following the Coulomb excitation of the 2(1)(+) were emitted in-flight and detected by the 64 BaF2 detectors of the Chateau de Cristal array. The relatively low B(E2) value of Ar-46 reported in this article supports the semi-magic character of this nucleus due to the persistence of the N = 28 shell closure at Z = 18.

The preliminary value of the reduced transition probability B(E2; 0+ ! 2+1 ) in 46Ar has been determined using the Coulomb excitation technique at intermediate energy. The 46Ar was produced in the fragmentation of a 48Ca beam at GANIL. The -rays following the Coulomb excitation of the 2+1 were emitted in-flight and detected by the 64 BaF2 detectors of the Château de Cristal array. The relatively low B(E2) value of 46Ar reported in this article supports the semi-magic character of this nucleus due to the persistence of the N = 28 shell closure at Z = 18.

For certain combinations of protons and neutrons, there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a "pear shape" in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation).In this paper, I will briefly review the historic evidence for reflection asymmetry in nuclei, describe how recent experiments carried out at REX-ISOLDE are constraining nuclear theory and how they contribute to tests of extensions of the Standard Model, and look at future prospects for this field.

The reduced transition probability B(E2: 3/2(-) -> 7/2(2)(-)) has been measured in S-43 using Coulomb excitation at intermediate energy. The nucleus of interest was produced by fragmentation of a Ca-48 beam at GANIL. The reaction products were separated in the LISE spectrometer. After Coulomb-excitation of S-43 in a Pb-208 target, the gamma rays emitted in-flight were detected by 64 BaF2 detectors of the Chateau de Cristal array. The preliminary value deduced for the reduced transition probability B(E2: 3/2(-) -> 7/2(2)(-)) is in agreement with the predictions of the shell model calculations and supports a prolate-spherical shape coexistence in the S-43 nucleus.

The 02(+) state in 34Si has been populated at the GANIL-LISE3 facility through the β decay of a newly discovered 1(+) isomer in 34Al of 26(1) ms half-life. The simultaneous detection of e(+)e(-) pairs allowed the determination of the excitation energy E(02(+))=2719(3)  keV and the half-life T(1/2)=19.4(7) ns, from which an electric monopole strength of ρ(2)(E0)=13.0(0.9)×10(-3) was deduced. The 2(1)(+) state is observed to decay both to the 0(1)(+) ground state and to the newly observed 0(2)(+) state [via a 607(2) keV transition] with a ratio R(2(1)(+)→0(1)(+)/2(1)(+)→0(2)(+))=1380(717). Gathering all information, a weak mixing with the 0(1)(+) and a large deformation parameter of β=0.29(4) are found for the 0(2)(+) state, in good agreement with shell model calculations using a new SDPF-U-MIX interaction allowing np-nh excitations across the N=20 shell gap.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Unveiling the intruder deformed 0_2 state in Si F. Rotaru, F. Negoita, S. Grévy, J. Mrazek, S. Lukyanov, F. Nowacki, A. Poves, O. Sorlin, C. Borcea, R. Borcea, et al.

We thank support by BMBFNo. 06BN109, GAof Czech Republic No. 202/040791, MEC-DGI-(Spain) No. BFM2003-1153, and by the EC through the Eurons Contract No. RII3-CT-3/2004- 506065 and OTKA No. K68801 and Bolyai Janos Foundation. R. B., A. B., M. L., S. I., F. N. and R. C., X. L. acknowledge the IN2P3/CNRS and EPSRC support

Received 23 February 2012DOI:https://doi.org/10.1103/PhysRevC.85.039901©2012 American Physical Society

The 0(2)(+) state in Si-34 has been populated at the GANIL-LISE3 facility through the beta decay of a newly discovered 1(+) isomer in Al-34 of 26(1) ms half-life. The simultaneous detection of e(+)e(-) pairs allowed the determination of the excitation energy E(0(2)(+)) = 2719(3) keV and the half-life T-1/2 = 19.4(7) ns, from which an electric monopole strength of rho(2)(E0) = 13.0(0.9) x 10(-3) was deduced. The 2(1)(+) state is observed to decay both to the 0(1)(+) ground state and to the newly observed 0(2)(+) state [via a 607(2) keV transition] with a ratio R(2(1)(+)) -> 0(1)(+)/2(1)(+) -> 0(2)(+)) = 1380(717). Gathering all information, a weak mixing with the 0(1)(+) and a large deformation parameter of beta = 0.29(4) are found for the 0(2)(+) state, in good agreement with shell model calculations using a new SDPF-U-MIX interaction allowing np-nh excitations across the N = 20 shell gap.