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The decay of the 21.47-MeV stretched resonance in $^{13}$C, arising from p3/2→d5/2 nucleon excitation coupled to maximum spin, was investigated in a (p,p′) experiment at 135 MeV proton bombarding energy, performed at the Cyclotron Centre Bronowice (CCB) at IFJ PAN in Krakow. First experimental information on the proton and neutron decay branches from this state was obtained by using coincidence measurement of protons inelastically scattered on a $^{13}$C target and γ rays from daughter nuclei, namely, $^{12}$B (proton decay) and $^{12}$C (neutron decay). The main branches lead to the Jπ=2+, first-excited state at 0.953 MeV in $^{12}$B, and to the Jπ=1+, T=1 level at 15.110 MeV in $^{12}$C. The results were compared with predictions from the Gamow Shell Model (GSM), which was used to describe the stretched resonance in terms of its energy, width, electromagnetic transition strengths and decay pattern. A very good agreement was obtained between the measured and calculated properties of the 21.47-MeV stretched resonance in $^{13}$C, demonstrating the high-quality and precision of the GSM wave function calculations, which include coupling to the resonant and non-resonant particle continuum.

A new measurement of γ decay from the states above the neutron threshold in Pb208 has been performed at Cyclotron Centre Bronowice in Kraków, Poland. The main goal of the experiment was to observe the γ decay to the ground state from the isoscalar giant quadrupole resonance (ISGQR). To this day, the only published observation of this phenomenon dates back to the late 1980s, where γ decay to the ground state branching ratio was reported. At variance with the existing measurement using inelastic scattering of O17, here proton inelastic scattering is employed. In particular, data were obtained for Pb208(p,p′γ) at 85 MeV beam energy, where γ rays were measured for proton scattering angles 8.9∘, 10.7∘, 12.5∘, and 14.3∘. By applying a similar analysis method as in the previous experiment, the branching ratio of ISGQR gamma decay to the ground state was extracted from the data.

The low-lying dipole strength in the $^{90,94}$Zr nuclei was investigated via (p,p′γ) at 80 MeV and (α,α′γ) at 130 MeV. The experiments, made at RCNP, used the magnetic spectrometer Grand Raiden for the scattered particles and the array CAGRA with HPGe detectors for the γ-decay. For $^{94}$Zr these are the first data for both reactions and for $^{90}$Zr these are the first data with (p,p′γ) and the first ones at high resolution for (α,α′γ). The comparison of the present results for the two nuclei with existing (γ,γ′) data shows that both nuclear probes produce an excitation pattern different than that of the electromagnetic probes.DWBA calculations were made using form factors deduced from transition densities, based on RPA calculations, characterized by a strong neutron component at the nuclear surface. A combined analysis of the two reactions was performed for the first time to investigate the isoscalar character of the 1$^{−}$ states in $^{90,94}$Zr. The (p,p′γ) cross section was calculated using values for the isoscalar electric dipole energy-weighted sum rule (E1 ISEWSR) obtained from the (α,α′γ) data. The isoscalar strength for $^{90}$Zr was found to exhaust 20 ± 2.5% of the EWSR in the energy range up to 12 MeV. In case of $^{94}$Zr, a strength of 9 ± 1.1% of the EWSR was found in the range up to 8.5 MeV.Although an overall general description was obtained in the studied energy intervals, not all proton cross sections were well reproduced using the isoscalar strength from (α,α′γ). This might suggest mixing of isoscalar and isovector components and that this mixing and the degree of collectivity are not the same for all the 1$^{−}$ states below the particle binding energy.

Physics letters / B 816, 136210 (2021). doi:10.1016/j.physletb.2021.136210, Published by North-Holland Publ., Amsterdam

The low-spin structure of the semimagic ^{64}Ni nucleus has been considerably expanded: combining four experiments, several 0^{+} and 2^{+} excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0^{+} excitation is located at a surprisingly high energy (3463 keV), with a collective 2^{+} state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N. ispartof: PHYSICAL REVIEW LETTERS vol:125 issue:10 ispartof: location:United States status: published

Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈70, N≈Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in As69 and Ge66 nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in As69 and Ge66 have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the S32(95MeV)+0.8mg/cm2 Ca40 fusion-evaporation reaction. The strongest reaction channels 3p and α2p led to the As69 and Ge66 final nuclei, respectively. Using γ-γ-recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In As69, the extracted lifetimes are τ=72 (-32, +45) fs for the 33/2+ state at 7897 keV and τ

International audience; Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈70, N≈Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in As69 and Ge66 nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in As69 and Ge66 have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the S32(95MeV)+0.8mg/cm2 Ca40 fusion-evaporation reaction. The strongest reaction channels 3p and α2p led to the As69 and Ge66 final nuclei, respectively. Using γ-γ-recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In As69, the extracted lifetimes are τ=72 (−32, +45) fs for the 33/2+ state at 7897 keV and τ

Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈ 70 , N≈ Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in 69 As and 66 Ge nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in 69 As and 66 Ge have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the 32 S ( 95 MeV ) + 0.8 mg / cm 2 40 Ca fusion-evaporation reaction. The strongest reaction channels 3p and α 2 p led to the 69 As and 66 Ge final nuclei, respectively. Using γ − γ -recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In 69 As , the extracted lifetimes are τ = 72 ( − 32 , +45 ) fs for the 33 / 2 + state at 7897 keV and τ < 85 fs for the 37 / 2 + state at 9820 keV. For the 66 Ge case, the lifetime of the 11 − state at 7130 keV is τ = 122 ( ± 41 ) fs. Lifetimes in 69 As and 66 Ge reported in this paper have been measured for the first time in the present experiment. Conclusions: The results are discussed in the terms of deformation and shape evolution in 69 As and 66 Ge . The quadrupole moments deduced from the measured lifetimes were compared with the cranked Woods-Saxon-Strutinsky calculations by means of the total Routhian surface method. It turns out that Band 3 in 69 As shows an oblate-prolate shape transition, and above spin 33 / 2 + it corresponds to a prolate collective structure with β 2 ≈ 0.27 and γ ≈ 20 ∘ . In turn, in 66 Ge the negative-parity band built on the 7− state at 4205 keV corresponds to a triaxial shape with β 2 = 0.33 and γ = 31 ∘ . Analysis of the transitional quadrupole moments derived from the experimental and theoretical ones points to a significant change of deformation in the 69 As and 66 Ge nuclei with increasing rotational frequency.

A Coulomb-excitation experiment to study electromagnetic properties of 42Ca was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in 42Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in 42Ca, including the diagonal E2 matrix elements of 2+ 1 and 2+ 2 states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 0+ 1,2 and 2+ 1,2 states, as well as triaxiality for 0+ 1,2 states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in 42Ca. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42Ca.

20 pags., 12 figs., 14 tabs., A Coulomb-excitation experiment to study electromagnetic properties of Ca42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in Ca42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca42, including the diagonal E2 matrix elements of 21+ and 22+ states, were determined using the least-squares code gosia. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 01,2+ and 21,2+ states, as well as triaxiality for 01,2+ states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca42., K.H.-K. acknowledges support from the Research Council of Norway under Grant No. 213442. T.R.R. acknowledges computing time at GSI-Darmstadt and support from Spanish MINECO under Programa Ramon y Cajal 11420 and FIS-2014-53434-P (T.R.R.). We also acknowledge the support by Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019 and by the FEDER funds of the European Commission (A. Gadea), Spanish Ministerio de Economía y Competitividad under contract FPA2014-57196-C5 (A. Jungclaus, A Gadea), German Bundesministerium für Bildung und Forschung (BMBF) under Contract No. 05P12PKFNE TP4 (B. Birkenbach), the Polish National Science Centre under Projects No. 2011/03/B/ST2/01894, No. DEC-2013/10/M/ST2/00427, No. 2013/08/M/ST2/00591, No. UMO-2014/14/M/ST2/00738 (COPIN-INFN Collaboration), No. 2015/17/B/ST2/01534, No. 2016/22/M/ST200269, the UK STFC under Grants No. ST/J000124/1 and No. ST/L005735/1. The EAGLE Collaboration thanks the European Gamma-Ray Spectroscopy Pool (GAMMAPOOL) for the loan of Ge detectors.

The γ decay from the high-lying states of Ce140 excited via inelastic scattering of O17 at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented ΔE-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1- states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1- pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

A study of fusion-evaporation and (partly) fusion-fission channels for the $^{88}$Mo compound nucleus, produced at different excitation energies in the reaction $^{48}$Ti + $^{40}$Ca at 300, 450 and 600 MeV beam energies, is presented. Fusion-evaporation and fusion-fission cross sections have been extracted and compared with the existing systematics. Experimental data concerning light charged particles have been compared with the prediction of the statistical model in its implementation in the Gemini++ code, well suited even for high spin systems, in order to tune the main model parameters in a mass region not abundantly covered by exclusive experimental data. Multiplicities for light charged particles emitted in fusion evaporation events are also presented. Some discrepancies with respect to the prediction of the statistical model have been found for forward emitted $\alpha$-particles; they may be due both to pre-equilibrium emission and to reaction channels (such as Deep Inelastic Collisions, QuasiFission/QuasiFusion) different from the compound nucleus formation., Comment: 14 pages, 14 figures

The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented Δ E-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1^− states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1^− pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

M. Krzysiek et al. ; 8 págs.; 7 figs. ; 2 tabs., The γ decay from the high-lying states of Ce140 excited via inelastic scattering of O17 at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented ΔE-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1- states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1- pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used. ©2016 American Physical Society, This work has been partly supported by the stipend from Marian Smoluchowski Krakow Research Consortium ’Matter-Energy-Future’ as a Leading National Research Center (KNOW) and also by several grants: the Polish National Science Centre under Contracts No. 2015/17/B/ST2/01534, No. 2013/09/N/ST2/04093, No. 2013/08/M/ST2/00591, and No. 2011/03/B/ST2/01894; US-NSF Grants No. PHY-1204486 and No. PHY-1404343; Croatian Science Foundation under Project No. IP-2014-09-9159; the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5-4-P. Also, A. Gadea has been supported by MINECO, Spain, under Grant No. FPA2014-57196-C5; Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019; and the EU under the FEDER program. The research leading to these results has also received funding from the European Union Seventh Framework Programme FP7/2007-2013 under Grant Agreement No. 262010 - ENSAR.

International audience; 2(+) and 1(-) states in Zr-90 were populated via the (O-17, O-17 'gamma) reaction at 340 MeV. The gamma decay was measured with high resolution using the AGATA (advanced gamma tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2(+), 3(,)(-) and 1(-) states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1(-) state at 6.424 MeV. The comparison of the present (17O, 17O 'gamma) data with existing (gamma,gamma') and (p, p') data in the corresponding region of the gamma continuum (6-11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy.