Octupole correlations in the structure of O2 bands in the N=88 nuclei150Sm Gd

Knowledge of the exact microscopic structure of the 01 + ground state and first excited 02 + state in 150Sm is required to understand the branching of double β decay to these states from 150Nd. The detailed spectroscopy of 150Sm and 152Gd has been studied using (α,xn) reactions and the γ -ray arrays AFRODITE and JUROGAM II. Consistently strong E1 transitions are observed between the excited Kπ = 02 + bands and the lowest negative parity bands in both nuclei. These results are discussed in terms of the possible permanent octupole deformation in the first excited Kπ = 02 + band and also in terms of the “tidal wave” model of Frauendorf.Web of Scienc

Determining the lifetime of the first 4⁺ state in ¹⁸²Pt

In this work the mean lifetime of the First 4+ state in 182Pt was determined by using the Recoil Distance Doppler-Shift method. The studied nuclei were produced in the 86Kr(100Mo, 4n)182Pt fusion-evaporation reaction. The RDDS method exploits the fact that the observed γ-ray energy depends on the velocity of the emitting nucleus. Using a degrader foil after the target enables measuring the intensities of γ-rays emitted before and after the degrader. The recoil-gated γγ spectra were analyzed separately for each target-to-degrader distance and the lifetime was determined with the Differential Decay Curve Method, which takes into account the lifetimes of the feeding states. The lifetime of the 4+ state in 182Pt was determined to be τ = 40:8(14) ps. This corresponds to a transition quadrupole moment of |Qt| = 6:90(12) eb. When comparing the quadrupole moment to other N = 104 isotones it is clear, even when taking into account the charge dependence of the quadrupole moment, that the quadrupole moment of the prolate 4+ state in 186Pb is significantly larger. Also the quadrupole moments decrease with decreasing Z. Before drawing any final conclusions about the collectivity of the prolate band in 182Pt it is neccessary to determine the lifetimes of other yrast excited states at low energies

Spectroscopy and lifetime measurements of ¹⁶⁶ ¹⁶⁸Os

Neutron-deficient osmium isotopes 166Os and 168Os have been studied with γ-ray spectroscopy and lifetime measurements. The level scheme of 166Os has been expanded with several new structures including second the 8+ and 10+ states. These states confirm the change in the structure of the yrast band between the 6+ and 8+ states. Lifetimes of the low-lying excited states have been measured in an RDDS measurement. The results reveal a sudden decrease in the collectivity when moving towards the neutron shell closure. While the 2+ → 0+ transition is still collective in 168Os, in 166Os the reduced transition probability is only few Weisskopf units, a value expected only at closed shells. In 168Os the 4+ → 2+ transition is remarkably less collective than the 2+ → 0+ transition. While nuclear models predict a decrease in collectivity, no modern calculations can explain the measured transition probabilities

Experimental study of 1/2(+) isomers in At-199,At-201

Using fusion-evaporation reactions, a gas-filled recoil separator, and recoil-electron and recoil-electron-α tagging techniques, a new isomeric 1 2 + state [T1/2 = 45(3) ms] in 201At is identified, and an earlier reported corresponding state [T1/2 = 273(9) ms] in 199At is confirmed. The 1 2 + state is suggested to originate from an intruder π(s1/2) −1 configuration. In addition, nuclear structure of states below and above this 1 2 + state are studied in both nuclei. The isomer decays through a cascade of an E3 transition followed by a mixed M1/E2 transition to the 9 2 − ground state, and it is interpreted to be fed from nearly spherical 3 2 + and 5 2 + states originating from π(d3/2) −1 and π(d5/2) −1 configurations, respectively.peerReviewe

Confirmation of the new isotope 178Pb

The extremely neutron-deficient isotope 178Pb has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the α decay of 178Pb and its α-decay chain through α-α correlations. The α decay was measured to have an energy and half-life of Eα= 7610(30) keV and t1/2 = 0.21+0.21 −0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The α-decay reduced width and hindrance factor for 178Pb were deduced and correspond to an unhindered l = 0 transition. In addition, the mass excess of 178Pb and the α-decay Q value were calculated from the experimental results and compared to theoretical values.peerReviewe

Decay spectroscopy of 179 82 Pb 97 and evidence for a 9/2− intruder state in 179 81 Tl 98

The very neutron-deficient isobars 179Pb and 179Tl have been produced using the fusion-evaporation reactions 104Pd(78Kr,xpyn), where x≤1 and y≥2. The gas-filled separator RITU was employed to transport and separate the recoiling nuclei of interest from the scattered beam and unwanted products. The GREAT spectrometer was used to study the decay properties through α−α and α−γ correlations, which has allowed the ground state of 179Pb to be assigned as Iπ=9/2−. The decay of 179Pb was measured to have an α-particle energy and half-life of Eα=7348(5)keV and t1/2=2.7(2) ms, respectively. A search for a νi13/2 state in 179Pb was performed, but only a limit of excitation energy and half-life was obtained. In 179Tl a t1/2=114+18−10 ns isomeric state, likely at an excitation energy of 904.5(9) keV, was identified and is tentatively assigned to be a 9/2− proton intruder state.peerReviewe

Quantum-state-selective decay spectroscopy of 213Ra

An experimental scheme combining the mass resolving power of a Penning trap with contemporary decay spectroscopy has been established at GSI Darmstadt. The Universal Linear Accelerator (UNILAC) at GSI Darmstadt provided a 48Ca beam impinging on a thin 170Er target foil. Subsequent to velocity filtering of reaction products in the Separator for Heavy Ion reaction Products (SHIP), the nuclear ground state of the 5n evaporation channel 213Ra was mass-selected in SHIPTRAP, and the 213Ra ions were finally transferred into an array of silicon strip detectors surrounded by large composite germanium detectors. Based on comprehensive geant4 simulations and supported by theoretical calculations, the spectroscopic results call for a revision of the decay path of 213Ra, thereby exemplifying the potential of a combination of a mass-selective Penning trap device with a dedicated nuclear decay station and contemporary geant4 simulations.peerReviewe

Experimental study of isomeric intruder ½+ states 197,203At

A newly observed isomeric intruder ½ + state [ T ½ = 3.5 ( 6 ) ms ] is identified in 203 At using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of E 3 and mixed M 1 / E 2 transitions to the 9 / 2 − ground state, and it is suggested to originate from the π ( s ½ ) − 1 configuration. In addition, the structures above the ½ + state in 203 At and 197 At are studied using in-beam γ -ray spectroscopy, recoil-decay tagging, and recoil-isomer decay tagging methods. The ½ + state is fed from 3 / 2 + and 5 / 2 + states, and the origin of these states are discussed.peerReviewe

Detailed spectroscopy of 195Bi

An experiment focused on the study of shape coexistence and new high-spin structures in 195 Bi has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the 13 / 2 + isomeric state was extended up to I π = ( 49 / 2 + ) and an energy of 5706 keV. The I π = 31 / 2 + member of the π i 13 / 2 band was also found to feed a new long-lived isomeric state with an excitation energy of 2616 keV and a spin and parity of I π = 29 / 2 + . The half-life of the 29 / 2 + isomeric state was determined to be 1.49 ( 1 ) μ s . It decays via the emission of 457-keV E 2 and 236-keV E 1 transitions, respectively. A low-energy 46-keV E 2 transition has been identified to depopulate the ( 29 / 2 − ) isomeric state, with a measured half-life of T 1 / 2 = 614 ( 5 ) ns . This transition allows the excitation energy of the isomeric state to be determined as 2381 keV. The feeding patterns of both 29 / 2 + and ( 29 / 2 − ) isomeric states have also been described. This is the first time collective structures have also been observed up to high spins and excitation energies in the neutron-deficient 195 Bi nucleus. Evidence for the manifestation of shape coexistence in 195 Bi is also discussed.peerReviewe

Spin-dependent evolution of collectivity in 112Te

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus 112Te has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations.peerReviewe