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The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in 127Cd and 129Cd for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably, this mechanism is found to act well beyond the h11/2 shell. [ABSTRACT FROM AUTHOR]

Excited states in 129I were populated with the 124Sn(7Li,2n) reaction at 23 MeV. In-beam measurements of γ-ray coincidences were performed with an array of eight HPGe detectors and five LaBr3(Ce) scintillation detectors. Based on the γγ coincidence data, a positive parity band structure built on the 7/2+ ground state was established and the nπg7/2 configuration at oblate deformation was assigned to it. The results are compared to interacting Boson-Fermion model (IBFM) and total Routhian surface (TRS) calculations. [ABSTRACT FROM AUTHOR]

Background: Nuclei in the A " 190 mass region show gradual shape changes from prolate through nonaxial deformed shapes and ultimately towards spherical shapes as the Pb region is approached. Exploring how this shape evolution occurs will help us understand the evolution of collectivity in this region. Purpose: The level scheme of the 192 Au nucleus in A "190 region was studied in order to deduce its deformations. Methods: High-spin states of 192Au have been populated in the 186W("B, 5n) reaction at a beam energy of 68 MeV and their ? decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory (WNSL), Yale University. Results: Based on double and triple ?-ray coincidence data the level scheme of 192 Au has been extended up to Ip = 32+ at an excitation energy of ~6 MeV. Conclusion: The results are discussed in the framework of pairing and deformation self-consistent total Routhian surface (TRS) and cranked shell model (CSM) calculations. The comparison of the experimental observations with the calculations indicates that this nucleus takes a nonaxial shape similar to other Au nuclei in this region. [ABSTRACT FROM AUTHOR]

The spectroscopic quadrupole moment of the T1/2=9.4(5) ns isomer in 193Pb at an excitation energy Eex=(2585+x) keV is measured by the time-differential perturbed angular distribution method as ∣Qx∣=2.6(3) e b. Spin and parity Iπ=27/2¯ are assigned to it based on angular distribution measurements. This state is the band head of a magnetic-rotational band, described by the 1i13/2 subshell with the (3s1/2-21h9/21i13/2)11- proton excitation. The pairing-plus-quadrupole tilted-axis cranking calculations reproduce the measured quadrupole moment with a moderate oblate deformation ϵ2=-0.11, similar to that of the 11¯proton intruder states, which nuclei in the region. This is the first direct measurement of a quadrupole moment and thus of the deformation of a magnetic-rotational band head. [ABSTRACT FROM AUTHOR]

The neutron-deficient cadmium isotopes have been measured by high-resolution laser spectroscopy at CERN-ISOLDE. The electromagnetic moments of 101Cd have been determined for the first time and the quadrupole-moment precision of 103Cd has been vastly improved. The results on the sequence of 5/2+ ground states in 101-109Cd are tentatively discussed in the context of simple structure in complex nuclei as similarities are found with the 11/2- states in the neutron-rich cases. Comparison with shell-model calculations reveals a prominent role of the two holes in the Z=50 core. [ABSTRACT FROM AUTHOR]

An empirical parametrization for the production cross sections of 238U photofission fragments at low energies (Eγ<30 MeV) is developed. This parametrization, GIF238U, consists of three parts, namely, the photofission cross section, the mass yield, and the isobaric charge distribution. The photofission cross section is parametrized to reproduce measured data over a wide energy range. The mass yield distribution is described by the energy-dependent multimodal fission model. The isobaric charge distribution is improved, relative to other parametrizations, to describe many experimental data sets over a broad mass range. Comparisons with different measured 238U photofission data sets at various energies reveal that GIF238U is in very good agreement with measured elemental and mass yields and can accurately reproduce experimental isotopic yields. Production cross sections (yields) of photofission fragments calculated by this parametrization indicate that many neutron-rich nuclei approaching the r-process path can be accessed via photofission of 238U at radioactive-beam facilities. [ABSTRACT FROM AUTHOR]

Isomer shifts have been determined in 111-129Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1/2+ and the 3/2+ ground states to the 11/2- isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory. [ABSTRACT FROM AUTHOR]

Post-accelerated isomerically purified radioactive beams, available at the CERN On-Line Isotope Mass Separator facility using the resonant ionization laser technique, have been used to study the Coulomb excitation of the I&pi; = 3- state in 70Cu (Z = 29, N = 41). While first results using a Iπ =6- beam were reported previously, the present complementary experiment allows us to complete the study of the multiplet of states (3-, 4- ,5-,6-) arising from the π2p3νlg9/2 configuration. Besides the known γ-ray transition deexciting the 4- state, a ground-state γ ray of 511(3) keV was observed for the first time and was unambiguously associated with the 5- state deexcitation. This observation fixes the energy, spin, and parity of this state, completing the low-energy level scheme of 70Cu. B(E2) values for all possible E2 transitions within the multiplet were determined. A comparison with large-scale shell model calculations using different interactions and valence spaces shows the importance of proton excitation across the Z = 28 shell gap and the role of the 2d5/2 neutron orbital. [ABSTRACT FROM AUTHOR]

Differences in mean-square nuclear charge radii of 100-130Cd are extracted from high-resolution collinear laser spectroscopy of the 5s ²S1/2→5p ²P3/2 transition of the ion and from the 5s5p ³P2→5s6s ³S1 transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete sdgh shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius. [ABSTRACT FROM AUTHOR]

Excited states of the neutron-rich nuclei 97,99Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of 97Rb as being built on the pg9/2 [431] 3/2+ Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around A~100 and indicates that the deformation of 97Rb is essentially the same as that observed well inside the deformed region. It further highlights the power of the Coulomb-excitation technique for obtaining spectroscopic information far from stability. The 99Rb case demonstrates the challenges of studies with very short-lived postaccelerated radioactive beams. [ABSTRACT FROM AUTHOR]

A precise measurement of the g factor of the first-excited state in the self-conjugate (N=Z) nucleus 24Mg is performed by a new time-differential recoil-in-vacuum method based on the hyperfine field of hydrogenlike ions. Theory predicts that the g factors of such states, in which protons and neutrons occupy the same orbits, should depart from 0.5 by a few percent due to configuration mixing and meson-exchange effects. The experimental result, g=0.538±0.013, is in excellent agreement with recent shell-model calculations and shows a departure from 0.5 by almost 3 standard deviations, thus achieving, for the first time, the precision and accuracy needed to test theory. Proof of the new method opens the way for wide applications including measurements of the magnetism of excited states of exotic nuclei produced as radioactive beams. [ABSTRACT FROM AUTHOR]

We report on the spectroscopic quadrupole moment measurement of the 7/2¡" isomeric state in "JgS27 [E* = 320.5(5) keV, Tt/2 = 415(3) ns], using the time dependent perturbed angular distribution tech-nique at the RIKEN RIBF facility. Our value, | Qs |= 23(3)

The high-velocity transient-field (HVTF) technique was used to measure the g factor of the 2+ state of 72Zn produced as a radioactive beam. The transient-field strength was probed at high velocity in ferromagnetic iron and gadolinium hosts using 76Ge beams. The potential of the HVTF method is demonstrated and the difficulties that need to be overcome for a reliable use of the TF technique with high-Z, high-velocity radioactive beams are revealed. The polarization of K-shell vacancies at high velocity, which shows more than an order of magnitude difference between Z = 20 and Z = 30 is discussed. The g-factor measurement hints at the theoretically predicted transition in the structure of the Zn isotopes near N = 40. [ABSTRACT FROM AUTHOR]

Photodisintegration reaction rates involving charged particles are relevant to the p-process nucleosynthesis that aims at explaining the production of stable neutron-deficient nuclides heavier than iron. In this study, considering the compound and pre-equilibrium reaction mechanisms, the cross sections and astrophysical rates of (γ,p) and (γ,α) reactions for about 3000 target nuclei with 10≤Z≤100 ranging from stable to proton dripline nuclei are computed. To study the sensitivity of the calculations to the optical model potentials (OMPs), both the phenomenological Woods-Saxon and the microscopic folding OMPs are taken into account. The systematic comparisons show that the reaction rates, especially for the (γ,α) reaction, are dramatically influenced by the OMPs. Thus, better determination of the OMP is crucial to reduce the uncertainties of the photodisintegration reaction rates involving charged particles. Meanwhile, a γ-beam facility at Extreme Light Infrastructure-Nuclear Physics (ELI-NP) is being developed which will open new opportunities to experimentally study the photodisintegration reactions of astrophysical interest. Considering both the important reactions identified by the nucleosynthesis studies and the purpose of complementing the experimental results for the reactions involving p nuclei, the measurements of six (γ,p) and eight (γ,α) reactions based on the γ-beam facility and the Extreme Light Infrastructure Silicon Strip Array (ELISSA) for the detection of charged particles at ELI-NP are proposed. Furthermore, the geant4 simulations on these (γ,p) and (γ,α) reactions are performed using the calculated cross sections and the features of the γ-beam facility and the ELISSA detector at ELI-NP. Simultaneously satisfying the minimum detectable limit of the experimental yield and the particle identification of protons and α particles, the minimum required energies of the γ beam to measure the six (γ,p) and eight (γ,α) reactions are estimated. It is shown that the direct measurements of these photonuclear reactions based on the γ-beam facility at ELI-NP within the Gamow windows at the typical temperature of T9=2.5 for the p-process are fairly feasible and promising. We believe that this pivotal work will guide the future photodisintegration experiments at ELI-NP. Furthermore, the expected experimental results will be used to constrain the OMPs of the charged particles, which can eventually reduce the uncertainties of the reaction rates for the p-process nucleosynthesis. [ABSTRACT FROM AUTHOR]

Excited states in ^{10}B were populated with the ^{10}B(p,p^{'}γ)^{10}B^{*} reaction at 8.5 MeV and their γ decay was investigated via coincidence γ-ray spectroscopy. The emitted γ rays were measured using large-volume LaBr&#95;{3}:Ce and CeBr&#95;{3} detectors placed in anti-Compton shields. This allowed the observation of weak γ-ray transitions, such as the M3 transition between the J^{π},T=0^{+},1 isobaric analog state (IAS) and the J^{π},T=3^{+},0 ground state and the E2 transition between the J^{π},T=2&#95;{1}^{+},0 state and the IAS, i.e., performing measurements of branching ratios at the level of λ≥10^{-4}. For the first time in ^{10}B, the competing M1 and M3 transitions from the decay of the IAS have been observed in a γ spectroscopy experiment. The experimental results are compared with ab initio no-core shell model calculation using the newest version of the local position-space chiral N^{3}LO nucleon-nucleon interaction. The calculations reproduce correctly the ordering of the bound states in ^{10}B, and are in reasonable agreement with the observed branching ratios and reduced transition probabilities.

The gyromagnetic factor of the low-lying E=251.96(9)  keV isomeric state of the nucleus ^{99}Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of J^{π}=7/2^{+}, with a half-life of T&#95;{1/2}=336(5)  ns. The isomer was produced and spin aligned via the abrasion-fission of a ^{238}U primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μ&#95;{N} was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd&#95;{5/2} composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

The change in mean-square nuclear charge radii δ⟨r^{2}⟩ along the even-A tin isotopic chain ^{108-134}Sn has been investigated by means of collinear laser spectroscopy at ISOLDE/CERN using the atomic transitions 5p^{2} ^{1}S&#95;{0}→5p6 s^{1}P&#95;{1} and 5p^{2} ^{3}P&#95;{0}→5p6s ^{3}P&#95;{1}. With the determination of the charge radius of ^{134}Sn and corrected values for some of the neutron-rich isotopes, the evolution of the charge radii across the N=82 shell closure is established. A clear kink at the doubly magic ^{132}Sn is revealed, similar to what has been observed at N=82 in other isotopic chains with larger proton numbers, and at the N=126 shell closure in doubly magic ^{208}Pb. While most standard nuclear density functional calculations struggle with a consistent explanation of these discontinuities, we demonstrate that a recently developed Fayans energy density functional provides a coherent description of the kinks at both doubly magic nuclei, ^{132}Sn and ^{208}Pb, without sacrificing the overall performance. A multiple correlation analysis leads to the conclusion that both kinks are related to pairing and surface effects.

Differences in mean-square nuclear charge radii of ^{100-130}Cd are extracted from high-resolution collinear laser spectroscopy of the 5s ^{2}S&#95;{1/2}→5p ^{2}P&#95;{3/2} transition of the ion and from the 5s5p ^{3}P&#95;{2}→5s6s ^{3}S&#95;{1} transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete sdgh shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius.

Isomer shifts have been determined in ^{111-129}Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1/2^{+} and the 3/2^{+} ground states to the 11/2^{-} isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.

Excited states of the neutron-rich nuclei (97,99)Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of (97)Rb as being built on the πg(9/2) [431] 3/2(+) Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around A∼100 and indicates that the deformation of (97)Rb is essentially the same as that observed well inside the deformed region. It further highlights the power of the Coulomb-excitation technique for obtaining spectroscopic information far from stability. The (99)Rb case demonstrates the challenges of studies with very short-lived postaccelerated radioactive beams.

The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in (127)Cd and (129)Cd for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2(-) quadrupole moments. Remarkably, this mechanism is found to act well beyond the h(11/2) shell.

We report on the spectroscopic quadrupole moment measurement of the 7/2(1)(-) isomeric state in (16)(43)S(27) [E*=320.5(5) keV, T(1/2)=415(3) ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, |Q(s)|=23(3) efm(2), is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured |Q(s)|, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape.

We report on the g-factor measurement of the first isomeric state in (16)43S27 [Ex=320.5(5) keV, T1/2=415(5) ns, and g=0.317(4)]. The 7/2- spin-parity of the isomer and the intruder nature of the ground state of the nucleus are experimentally established for the first time, providing direct and unambiguous evidence of the collapse of the N=28 shell closure in neutron-rich nuclei. The shell model, beyond the mean-field and semiempirical calculations, provides a very consistent description of this nucleus showing that a well deformed prolate and quasispherical states coexist at low energy.

The electric quadrupole moment and the magnetic moment of the 11Li halo nucleus have been measured with more than an order of magnitude higher precision than before, |Q| = 33.3(5) mb and mu = +3.6712(3)muN, revealing a 8.8(1.5)% increase of the quadrupole moment relative to that of 9Li. This result is compared to various models that aim at describing the halo properties. In the shell model an increased quadrupole moment points to a significant occupation of the 1d orbits, whereas in a simple halo picture this can be explained by relating the quadrupole moments of the proton distribution to the charge radii. Advanced models so far fail to reproduce simultaneously the trends observed in the radii and quadrupole moments of the lithium isotopes.

Collective properties of the low-lying levels in the odd-A 67-73Cu were investigated by Coulomb excitation with radioactive beams. The beams were produced at ISOLDE and postaccelerated by REX-ISOLDE up to 2.99 MeV/u. In 67,69Cu, low-lying 1/2(-), 5/2(-), and 7/2(-) states were populated. In 71,73Cu, besides the known transitions deexciting the single-particle-like 5/2(-) and core-coupled 7/2(-) levels, gamma rays of 454 and 135 keV, respectively, were observed for the first time. Based on a reanalysis of beta-decay work and comparison with the systematics, a spin 1/2(-) is suggested for these excited states. Three B(E2) values were determined in each of the four isotopes. The results indicate a significant change in the structure of the odd-A Cu isotopes beyond N=40 where single-particle-like and collective levels are suggested to coexist at very low excitation energies.

We report on the first low-energy Coulomb excitation measurements with radioactive Ipi=6- beams of odd-odd nuclei 68,70Cu. The beams were produced at ISOLDE, CERN and were post-accelerated by REX-ISOLDE to 2.83 MeV/nucleon. Gamma rays were detected with the MINIBALL spectrometer. The 6- beam was used to study the multiplet of states (3-, 4-, 5-, 6-) arising from the pi2p3/2 nu 1g9/2 configuration. The 4- state of the multiplet was populated via Coulomb excitation and the B(E2;6--->4-) value was determined in both nuclei. The results obtained illustrate the fragile stability of the Z=28 shell and N=40 subshell closures. A comparison with large-scale shell-model calculations using the 56Ni core shows the importance of the proton excitations across the Z=28 shell gap to the understanding of the nuclear structure in the neutron-rich nuclei with N approximately 40.

Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F,4n)134Pr. Recoil distance Doppler-shift and Doppler-shift attenuation measurements using the Euroball spectrometer, in conjunction with the inner Bismuth Germanate ball and the Cologne plunger, were performed at beam energies of 87 MeV and 83 MeV, respectively. Reduced transition probabilities in 134Pr are compared to the predictions of the two quasiparticle + triaxial rotor and interacting boson fermion-fermion models. The experimental results do not support the presence of static chirality in 134Pr underlying the importance of shape fluctuations. Only within a dynamical context the presence of intrinsic chirality in 134Pr can be supported.

We report on the g factor measurement of an isomer in the neutron-rich (61)(26)Fe (E(*)=861 keV and T(1/2)=239(5) ns). The isomer was produced and spin aligned via a projectile-fragmentation reaction at intermediate energy, the time dependent perturbed angular distribution method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the nuclear spin ensemble has been observed, allowing a precise determination of its g factor, including the sign: g=-0.229(2). In this way we open the possibility to study moments of very neutron-rich short-lived isomers, not accessible via other production and spin-orientation methods.

The quadrupole moment of the 11(-) isomer in 196Pb has been measured by the level mixing spectroscopy method. This state has a pi(3s(-2)(1/2)1h(9/2)1i(13/2))11(-) configuration which is involved in most of the shears band heads in the Pb region. The first directly measured value of Q(s)(11(-)) = (-)3.41(66) b, coupled to the previously known quadrupole moment of the nu(1i(-2)(13/2))12(+) isomer allows us to estimate the quadrupole moment of the 16(-) shears band head as Q(s)(16(-)) = -0.32(10) b. The experimental values are compared to tilted axis cranking calculations, giving insight into the validity of the additivity approach to couple quadrupole moments and on the amount of deformation in the shears bands.

The spectroscopic quadrupole moment of the high-spin, high- K five-quasiparticle isomer (K(pi) = 35/2(-), T(1/2) = 750(80) ns, E(i) = 3349 keV) in (179)W has been determined using the level mixing spectroscopy method. A value Q(s) = 4.00(+0.83-1.06)e b was derived, which corresponds to an intrinsic quadrupole moment Q0 = 4.73(+0.98-1.25)e b and to a quadrupole deformation beta(2) = 0.185(+0.038-0.049). These values differ significantly from the deduced ground-state quadrupole moments and are in disagreement with the current theoretical predictions in this mass region.