Projectile Coulomb excitation of the nucleus 194Pt

Low-lying collective excited states of 194Pt have been studied via the 12C(194Pt,194Pt*) projectile Coulomb excitation reaction at 85% of the Coulomb barrier (850 MeV) using the Gammasphere Ge-detector array at Argonne National Laboratory. Absolute E2 transition strengths have been obtained from the Coulex cross sections that were deduced from the relative γ-ray yields. They are discussed with respect to the structure suggested by the O(6) symmetry of the Interacting Boson Model

Low-energy structure of the even-A 96−104 Ru isotopes via g-factor measurements

The transient-field-perturbed angular correlation technique was used with Coulomb excitation in inverse kinematics to perform a systematic measurement of the g factors of the first excited 21+ states in the stable even-A isotopes Ru96-104. The measurements have been made relative to one another under matched kinematic conditions and include a measurement of g(21+)=+0.47(3) in Ru96

Properties of excited states in Ge77

The nucleus Ge77 was studied through the Ge76(C13,C12)Ge77 reaction at a sub-Coulomb energy. The angular distributions of γ rays depopulating excited states in Ge77 were measured in order to constrain spin and parity assignments. Some of these assignments are of use in connection with neutrinoless double beta decay, where the population of states near the Fermi surface of Ge76 was recently explored using transfer reactions

Low-lying quadrupole collective states of the light and medium Xenon isotopes

Collective low lying levels of light and medium Xenon isotopes are deduced from the Generalized Bohr Hamiltonian (GBH). The microscopic seven functions entering into the GBH are built from a deformed mean field of the Woods-Saxon type. Theoretical spectra are found to be close to the ones of the experimental data taking into account that the calculations are completely microscopic, that is to say, without any fitting of parameters.Comment: 8 pages, 4 figures, 1 tabl

Multinucleon transfer in the interaction of 977 MeV and 1143 MeV Hg 204 with Pb 208

A previous study of symmetric collisions of massive nuclei has shown that current models of multinucleon transfer (MNT) reactions do not adequately describe the transfer product yields. To gain further insight into this problem, we have measured the yields of MNT products in the interaction of 977 (E/A=4.79 MeV) and 1143 MeV (E/A=5.60 MeV) Hg204 with Pb208. We find that the yield of multinucleon transfer products are similar in these two reactions and are substantially lower than those observed in the reaction of 1257 MeV (E/A=6.16 MeV) Hg204+Pt198. We compare our measurements with the predictions of the GRAZING-F, dinuclear systems (DNS), and improved quantum molecular dynamics (ImQMD) models. For the observed isotopes of the elements Au, Hg, Tl, Pb, and Bi, the measured values of the MNT cross sections are orders of magnitude larger than the predicted values. Furthermore, the various models predict the formation of nuclides near the N=126 shell, which are not observed

Two-quasiparticle structures and isomers in Er168, Er170, and Er172

The stable and neutron-rich isotopes Er168, Er170, and Er172 have been studied with Gammasphere using inelastic excitation with energetic Xe136 beams. The previously assigned structures based on the proposed Kπ=4- isomeric intrinsic states in both Er168 and Er170 have been re-evaluated and an equivalent band identified in Er172. In Er170, the identification of a Kπ=6- band with transitions close in energy to those of the 4 - band leads to a modified interpretation, since the overlap would have compromised previous analyses. The gK-gR values for the 4- bands deduced from the in-band γ-ray intensities for the sequence of isotopes suggest a predominantly two-neutron configuration in Er168, an equally mixed two-neutron, two-proton configuration in Er170, and a two-proton configuration in Er172. A comprehensive decay scheme for the previously proposed 6+ isomer in Er172 has also been established, as well as band structures built on this isomer that closely resemble the 6+ and 7- two-neutron structures known in the isotone Yb174. The implied K hindrances are discussed. The main decay path of the 6+ isomer occurs through the newly identified 4- isomer. The measured lifetimes of the 4 - and 6+ isomers in Er172 are 57(3) and 822(90) ns, respectively. Multiquasiparticle calculations support the suggested configuration changes across the isotopic chain

Precise electromagnetic tests of ab initio calculations of light nuclei: States in Be10

In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in Be10 using the Doppler shift attenuation method (DSAM) following the Li7(Li7,α)Be10 reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The Jπ=21+ state at 3.37 MeV has τ=205±(5)stat±(7)sysfs corresponding to a B(E2) of 9.2(3)e2fm4 in broad agreement with many calculations. The Jπ=22+ state at 5.96 MeV was found to have a B(E2) of 0.11(2)e2fm4 and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment

Lifetime of the Kπ=8- isomer in the neutron-rich nucleus Er174, and N=106 E1 systematics

Chopped-beam techniques and γ-ray spectroscopy with Gammasphere have been used to measure the lifetime of the 1112-keV 8- isomeric state in Er174. The value obtained of τ=5.8(4) s corresponds to a reduced hindrance of fν=98 for the 163-keV E1 transition to the 8+ state of the ground-state band, in good agreement with the systematics of the corresponding E1 strengths in the N=106 isotones. The K-mixing in the 8- states is calculated in the context of the particle-rotor model and used to extract the underlying reduced hindrances

Xe 136 + Pb 208 reaction: A test of models of multinucleon transfer reactions

The yields of over 200 projectile-like fragments (PLFs) and target-like fragments (TLFs) from the interaction of (Ec.m.=450 MeV) Xe136 with a thick target of Pb208 were measured using Gammasphere and off-line γ-ray spectroscopy, giving a comprehensive picture of the production cross sections in this reaction. The measured yields were compared to predictions of the grazing model and the predictions of Zagrebaev and Greiner using a quantitative metric, the theory evaluation factor tef. The grazing model predictions are adequate for describing the yields of nuclei near the target or projectile but they grossly underestimate the yields of all other products. The predictions of Zagrebaev and Greiner correctly describe the magnitude and maxima of the observed TLF transfer cross sections for a wide range of transfers (ΔZ=-8 to ΔZ=+2). However, for ΔZ=+4, the observed position of the maximum in the distribution is four neutrons richer than the predicted maximum. The predicted yields of the neutron-rich N=126 nuclei exceed the measured values by two orders of magnitude. Correlations between TLF and PLF yields are discussed

High-spin transition quadrupole moments in neutron-rich Mo and Ru nuclei: Testing γ softness?

The transition quadrupole moments, Qt, of rotational bands in the neutron-rich, even-mass 102-108Mo and 108-112Ru nuclei were measured in the 8-16 ℏ spin range with the Doppler-shift attenuation method. The nuclei were populated as fission fragments from 252Cf fission. The detector setup consisted of the Gammasphere spectrometer and the HERCULES fast-plastic array. At moderate spin, the Qt moments are found to be reduced with respect to the values near the ground states. Attempts to describe the observations in mean-field-based models, specifically cranked relativistic Hartree-Bogoliubov theory, illustrate the challenge theory faces and the difficulty to infer information on γ softness and triaxiality from the data