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We measured the lifetimes of the 2+1,2 and 4+1 states in 98Ru in order to reduce their uncertainties and resolve the discrepancies in the literature for the lifetime of the 4f state. Coulomb excitation in inverse kinematics was used to populate excited states in 98Ru, and the recoil distance doppler shift (RDDS) method was employed using the nNew Yale plunger device (NYPD). This technique combined with inverse Coulomb excitation requires several corrections due to relativistic and deorientation effects but yields high precision lifetimes. The determined B4/2 = B(4+1 → 2)+/B(2+1 → O+1) = 1.86(16) agrees well with the vibrational limit. In order to analyze the data, a new method for the deorientation correction of RDDS data was developed using the perturbation of experimental angular correlations. The simultaneous measurement of deorientation and lifetime of a given state and its application are discussed. The method is suitable for radioactive beam experiments. [ABSTRACT FROM AUTHOR]

Background: One-phonon mixed-symmetry quadrupole excitations are a well-known feature of near-spherical, vibrational nuclei. Their interpretation as a fundamental building block of vibrational structures is supported by the identification of multiphonon states resulting from a coupling of fully-symmetric and mixed-symmetric quadrupole phonons. In addition, the observation of strong M1 transitions between low-lying 3- and 4+ states has been interpreted as an evidence for one-phonon mixed-symmetry excitations of octupole and hexadecapole character. Purpose: The aim of the present study is to identify collective one- and two-phonon excitations in the heaviest stable N = 52 isotone 96Ru based on a measurement of absolute Ail, E1, and E2 transition strengths. Methods: Inelastic proton-scattering experiments have been performed at the Wright Nuclear Structure Laboratory (WNSL), Yale University, and the Institute for Nuclear Physics (IKP), University of Cologne. From the acquired proton-γ and γγ coincidence data we deduced spins of excited states, y-decay branching ratios, and multipole mixing ratios, as well as lifetimes of excited states via the Doppler-shift attenuation method (DSAM). Results: Based on the new experimental data on absolute transition strengths, we identified the 2+ and 3+ members of the two-phonon mixed-symmetry quintuplet (21ms+⊙21ms+).Furthermore, we observed strong M1 transitions between low-lying 3- and 4+ states suggesting one-phonon symmetric and mixed-symmetric octupole and hexadecapole components in their wave functions, respectively. The experimental results are compared to sdg-IBM-2 and shell-model calculations. Conclusions: Both the sdg-IBM-2 and the shell-model calculations are able to describe key features of mixed-symmetry excitations of 96Ru. Moreover, they support the one-phonon mixed-symmetry hexadecapole assignment of the experimental 42+ state. [ABSTRACT FROM AUTHOR]

It was shown that the evolution of the B(E2; 2+1 0+1) values in N = 80 isotones from Te to Nd is affected by the underlying subshell structure. This manifests itself in the observation of the local suppression of the B(E2) value at Z = 58 with respect to the neighboring nuclei 136Ba and l40Nd. To investigate this shell sensitivity toward the Z = 64 subshell gap, the fi(E2+1 → 0+1) value of the unstable nucleus l42Sm was measured utilizing the projectile Coulomb excitation technique. The radioactive ion beam (RIB) experiment was performed at the REX-ISOLDE facility at CERN. The B(E2) value of 32 (4) W.u. reflects the impact of the πr(1g7/22d5/2) subshell closure at Z = 64 with respect to a linear scaling of collectivity with valence proton number. [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]

Background: Excitations with mixed proton-neutron symmetry have been previously observed in the N = 52 isotones. Besides the well-established quadrupole mixed-symmetry states (MSS), octupole and hexadecapole MSS have been recently proposed for the nuclei 92Zr and 94Mo. Purpose: The heaviest stable N = 52 isotone 96Ru was investigated to study the evolution of octupole and hexadecapole MSS with increasing proton number. Methods: Two inelastic proton-scattering experiments on 96Ru were performed to extract branching ratios, multipole mixing ratios, and level lifetimes. From the combined data, absolute transition strengths were calculated. Results: Strong M1 transitions between the lowest-lying 3- and 4+ states were observed, providing evidence for a one-phonon mixed-symmetry character of the 32(-) and 42+ states. Conclusions: sdg-IBM-2 calculations were performed for 96Ru. The results are in excellent agreement with the experimental data, pointing out a one-phonon hexadecapole mixed-symmetry character of the 42+ state. The 〈31-||M1||32(-)〉 matrix element is found to scale with the 〈2s+||M1||2ms+〉 matrix element. [ABSTRACT FROM AUTHOR]

A yy angular-correlatio n experiment has been performed to investigate the low-energy states of the nucleus 98Mo. The new data, including spin assignments, multipole mixing ratios, and lifetimes reveal evidence for shape coexistence and mixing in 98Mo, arising from a proton intruder configuration. This result is reproduced by a theoretical calculation within the proton-neutron interacting boson model with configuration mixing, based on microscopic energy density functional theory. The microscopic calculation indicates the importance of the proton particle-hole excitation across the Z = 40 subshell closure and the subsequent mixing between spherical vibrational and the y-soft equilibrium shapes in 98Mo. [ABSTRACT FROM AUTHOR]

Background: The interplay between single-particle and collective excitations in the 30 = Z = 40 and 30 = N = 50 even-even isotopes has been examined in light of recent new measurements of magnetic moments of 41+, 22+, and 21+ states. Purpose: The g factors of the 41+ and 22+ states in the 72,74,76Ge isotopes have been measured for the first time and the g(21+) values have been remeasured. Methods: The transient field (TF) technique in inverse kinematics with a variety of targets has been applied, following Coulomb excitation of the relevant states. The data have been analyzed within the framework of the IBA-II model. Large-scale shell-model calculations have been performed within the p3/2, p1/2, f5/2, g9/2 orbital space for both protons and neutrons with the JUN45 and JJ4B interactions. Results: The measured Ge g factors were compared to the g factors of the low-lying states of the neighboring Zn, Ge, Se, Kr, and Sr isotopes. The results were evaluated in the context of the systematics of g factors in the A ~ 80 region. Conclusions: The predictions based on the classic collective model and the interacting boson model IBA-II agree with the experimental results. No evidence for shell closure was found for neutrons at N = 38 or N = 40. [ABSTRACT FROM AUTHOR]

Excited states in 74 Se were populated following thee ε/β+ decay of 74Br, mainly from the J = K = 4,13.8-keV β-decaying isomer. Off-beam y-ray spectroscopy was performed with the array of Clover HPGe detectors at WNSL Yale. Many new transitions were observed and rigorous spin assignments were made based on y-y angular correlations. The β-decay strength was found to proceed almost entirely to a few high-lying states near 4500 keV, which are consistent with deformed two-quasineutron high-AT configurations. These doorway states then provide an effective tool for populating and identifying the lower prolate structures. Once categorized, the low-lying states of 74Se can be described as a set of near-spherical vibrational levels mixing strongly with a spectrum of prolate states which have an unperturbed bandhead near 1350 keV. [ABSTRACT FROM AUTHOR]

Precise electromagnetic transition matrix elements in 10Be and 10C have provided surprisingly stringent tests of modern ab initio calculations using realistic nuclear forces. The analog transition in 10B can further constrain these new calculations and probe the symmetry of the wave functions across the A = 10 multiplet. We report on a careful measurement of the β-ray intensities from states populated in the 10B(p,p') reaction at 10 MeV, including a determination of the key E2 branch from the J = 2 T = 1 state at 5164 keV to the J = 0 T = 1 state at 1740 keV of 0.16(4)%. [ABSTRACT FROM AUTHOR]

Background: The evolution of and interplay between single-particle and collective excitations in the 40 ≤ N ≤ 50 range for 38Sr and 40Zr isotopes have been studied. Purpose: Measurement of the g factor of the 2+1 and 4+1 states in radioactive 88Zr while simultaneously remeasuring the g(2+1) factors in the Sr isotopes and extention of the measurements to higher energy states in the Sr isotopes. Lifetimes of states in these nuclei are determined. Methods: The transient field technique in inverse kinematics and line-shape analysis using the Doppler-shift attenuation method are applied. The 88Zr nuclei were produced by the transfer of an a particle from the 12C nuclei of the target to 84Sr nuclei in the beam. The excited states in the stable 84Sr isotopes were simultaneously populated via Coulomb excitation by 12C in the same target. Coulomb excitation measurements on 86,88Sr were carried out with the same apparatus. Results: The resulting g factors and B(E2) values of these nuclei reveal similarities between the two chains of Zr and Sr isotopes. Large-scale shell-model calculations were performed within the p3/2, f5/2, P1/2. g9/2 orbital space for both protons and neutrons and yielded results in agreement with the experimental data. Conclusions: In this paper the magnetic moments and lifetimes of several low-lying states in 88Zr and 84,86,88Sr have been measured and compared to large-scale shell-model calculations. [ABSTRACT FROM AUTHOR]

Background: The experimental study of g(I > 2) factors of nuclear states can provide information about the evolution of collectivity in certain regions of the nuclear chart, and assist in obtaining a microscopic description of the nuclear wave functions. The measurements and explanations of g{I > 2) factors are still a challenge for experiments and theory. Purpose: Measurement of the g(2+1) and g(41) factors, the latter for the first time, in the 9644Ru nucleus. Comparison of the experimental results with calculations using the shell model and collective models. Methods: The experiments made use of the transient field technique, using a Coulomb-excitation reaction in inverse kinematics. Large scale shell model calculations were performed; comparisons with previous theoretical predictions, using the tidal-wave model and the hydrodynamical model, were carried out. Results: The values of g(2+1) = +0.46(2) and g(4+-) = +0.58(8) were experimentally obtained. While the g(2+1) value agrees with the hydrodynamical model prediction of g = Z/A = +0.46. the g(4+1 ) is in agreement with the shell model predictions. The trend of the experimental g factors, as a function of nuclear spin, is not reproduced by the theoretical models discussed. Conclusions: Measurements of g(2+1 ) and g(4+1 ) in 96Ru were performed. Further theoretical efforts are necessary to explain the trend of the g factors as a function of nuclear spin for the 96Ru nucleus. Future measurements of g(4+1) should reduce the uncertainty of the result. [ABSTRACT FROM AUTHOR]

Octupole vibrational states were studied in the nucleus 150Nd via inelastic proton scattering with 10.9-MeV protons, which are an excellent probe to excite natural parity states. For the first time in 150Nd, both the scattered protons and the γ rays were detected in coincidence, giving the possibility to measure branching ratios in detail. Using the coincidence technique, the B(E1) ratios of the decaying transitions for 10 octupole vibrational states and other negative-parity states to the yrast band were determined and compared to the Alaga rule. The positive and negative-parity states revealed by this experiment are compared with interacting boson approximation calculations performed in the spdf boson space. The calculations are found to be in good agreement with the experimental data, for both positive and negative-parity states. [ABSTRACT FROM AUTHOR]

The g factors of the first 2+ and 4+ states of the radioactive 100Pd nucleus have been investigated for the first time, using an α-particle transfer reaction from 12C to 96Ru. The transient magnetic field technique in inverse kinematics was used. The Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. nucleus is a suitable candidate for studying single-particle proton and neutron effects in the nuclear wave functions near the N = Z = 50 shell closures. The results are discussed within the frameworks of both large-scale shell-model calculations and collective-model predictions. [ABSTRACT FROM AUTHOR]

We report on the measurement of the ^{7}Be(n,p)^{7}Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a ^{7}Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal ^{7}Li(p,n)^{7}Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. The relevance of these results on the near-threshold neutron production in the p+^{7}Li reaction is also discussed.

The neutron-rich nuclei 94,96Kr were studied via projectile Coulomb excitation at the REX-ISOLDE facility at CERN. Level energies of the first excited 2(+) states and their absolute E2 transition strengths to the ground state are determined and discussed in the context of the E(2(1)(+)) and B(E2;2(1)(+)→0(1)(+)) systematics of the krypton chain. Contrary to previously published results no sudden onset of deformation is observed. This experimental result is supported by a new proton-neutron interacting boson model calculation based on the constrained Hartree-Fock-Bogoliubov approach using the microscopic Gogny-D1M energy density functional.