Search results for "nuclear physics"
showing 10 items of 5307 documents
Spectroscopy of the proton drip-line nucleus 203Fr
2013
The nucleus 203Fr has been studied through γ -ray and electron spectroscopy, using the recoil-decay tagging technique. A 13/2+ state, with a half-life of 0.37(5) μs, has been observed in 203Fr. Both the α-decay branch and the internal de-excitation of the 1/2+ isomer in 203Fr have been studied. Furthermore, the corresponding 1/2+ state, with a half-life of 0.31(8) s, has been found in 199At. In addition, transitions feeding the 9/2− ground state of 203Fr have been identified. The observed level pattern suggests that the ground state is still spherical. peerReviewed
Octupole correlations in the structure of 0$_2^+$ bands in the N=88 nuclei 150Sm and 152Gd
2013
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. peerReviewed
First prompt in-beam gamma-ray spectroscopy of a superheavy element: the 256Rf
2013
Using state-of-the-art γ-ray spectroscopic techniques, the first rotational band of a superheavy element, extending up to a spin of 20 ¯h, was discovered in the nucleus 256Rf. To perform such an experiment at the limits of the present instrumentation, several developments were needed. The most important of these developments was of an intense isotopically enriched 50Ti beam using the MIVOC method. The experimental set-up and subsequent analysis allowed the 256Rf ground-state band to be revealed. The rotational properties of the band are discussed and compared with neighboring transfermium nuclei through the study of their moments of inertia. These data suggest that there is no evidence of a…
Beta-delayed fission of 186, 188Bi isotopes
2013
By using the technique of correlating implanted evaporation residues and their subsequent fission decay, β-delayed fission (βDF) of 186Bi has been identified for the first time and βDF of 188Bi has been unambiguously confirmed. The experiments were performed at the velocity filter SHIP (GSI, Darmstadt). The βDF probabilities for both nuclides were qualitatively estimated, and, in particular indications for a large value in the case of 186Bi are regarded. peerReviewed
Local suppression of collectivity in the N=80 isotones at the Z=58 subshell closure
2013
Background: Recent data on N=80 isotones have suggested that the proton π(1g7/2) subshell closure at Z=58 has an impact on the properties of low-lying collective states. Purpose: Knowledge of the B(E2;2+1→0+1) value of 140Nd is needed in order to test this conjecture. Method: The unstable, neutron-rich nucleus 140Nd was investigated via projectile Coulomb excitation at the REX-ISOLDE facility with the MINIBALL spectrometer. Results: The B(E2) value of 33(2) W.u. expands the N=80 systematics beyond the Z=58 subshell closure. Conclusions: The measurement demonstrates that the reduced collectivity of 138Ce is a local effect possibly due to the Z=58 subshell closure and requests refined theoret…
Gamma-ray linear polarization measurement and $(g9/2)-3$ neutron alignment in 91Ru
2013
Linear polarization measurements have been performed for γ rays in 91Ru produced with the 58Ni(36Ar, 2p1nγ ) 91Ru reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the γ -γ coincidences, γ -ray linear polarization, and γ -ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3–1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in 91Ru. More specifically, calculations using a semiempirical…
Recoil-beta tagging study of the N=Z nucleus 66As
2013
An in-beam study has been performed to further investigate the known isomeric decays and to identify T = 1 excited states in the medium-heavy N = Z = 33 nucleus 66As. The fusion-evaporation reaction 40Ca(28Si,pn) 66As was employed at beam energies of 75 and 83 MeV. The half-lives and ordering of two known isomeric states in 66As have been determined with improved accuracy. In addition, several prompt γ -ray transitions from excited states, both bypassing and decaying to the isomeric states in 66As, have been observed. Most importantly, candidates for the 4+ → 2+ and 6+ → 4+ transitions in the T = 1 band have been identified. The results are compared with shell-model calculations using the m…
Isomer-tagged differential-plunger measurements in 113Xe
2013
The 278-keV M2 γ decay from the νh11/2 isomeric state in 113Xe has been observed for the first time using the recoil-isomer tagging technique. The half-life of the isomer has been measured to be 6.9(3) μs. The derived B(M2) value is in agreement with the trend of systematic measurements of M2 transition strengths in neutron-deficient tellurium and tin isotopes. The lifetime of the first excited state in the νh11/2 band has been measured using the recoil distance Doppler-shift method. The extracted B(E2) value has been compared to theoretical CD-Bonn calculations and recent lifetime measurements in 109Te. This comparison of B(E2) values has been used to shed light on the possible influence o…
Competing single-particle and collective states in the low-energy structure of 113I
2013
To understand the low-energy structure of the neutron deficient iodine isotopes, lifetimes for the low-lying 9/2+ and 11/2+ positive-parity states in 113I have been measured as τ = 28(4) ps and τ = 3.7(7) ps, respectively. The lifetime for the 11/2− state, which feeds the 9/2+ and 11/2+ states, was remeasured with improved accuracy as τ = 216(7) ps. The reduced transition probability, B(E2) = 32(5) W.u., for the 9/2+ → 5/2+ transition agrees with that calculated within the shell model using a Hamiltonian based on the charge-dependent Bonn nucleon-nucleon interaction. In contrast, the much larger transition probability, B(E2) = 209(39) W.u., measured for the 11/2+ → 7/2+ transition has been …
Total absorption study of the \beta decay of 102,104,105Tc
2013
The β-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely 102,104,105Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations. peerReviewed