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Rapid shape evolutions near A = 100 are now the focus of much attention in nuclear science. Much of the recent work has been centered on isotopes with Z

Swedish Research Council; European Community [HPRI-CT 1999-00019]; Spanish MINECO [FPA2015-65035-P]

gamma-ray and fast-timing spectroscopy were used to study levels in Al-30 populated following the beta(-) decay of Mg-30. Five new transitions and three new levels were located in Al-30. A search was made to identify the third 1(+) state expected at an excitation energy of similar to 2.5 MeV. Two new levels were found, at 3163.9 and 3362.5 keV, that are firm candidates for this state. Using the advanced time-delayed (ATD) beta gamma gamma (t) method we have measured the lifetime of the 243.8-keV state to be T-1/2 = 15(4) ps, which implies that the 243.8-keV transition is mainly of M1 character. Its fast B(M1; 2(+) -> 3(+)) value of 0.10(3) W.u. is in very good agreement with the USD shell-model prediction of 0.090 W.u. The 1801.5-keV level is the only level observed in this study that could be a candidate for the second excited 2(+) state.

10 pags.; 6 figs.; 4 tabs. ; Open Access funded by Creative Commons Atribution Licence 4.0, We have applied the fast timing β(t) technique to remeasure lifetimes of selected states in Ra populated in the β decay of Fr. T = 587(12) ps and 210(13)ps have been obtained for the 3/2 and 5/2 states at 50.1 and 79.7 keV, that are more accurate than the previous values of 630(70)ps and 166(55)ps, respectively. Our |D| value of 0.155(10) e·fm obtained for the K=3/2 configuration together with the available values of |D| for the K=1/2 and K=5/2 parity doublet bands establish the configuration dependence of |D| at low spins in this nucleus. Results of theoretical calculations performed for Ra, using the quasiparticle-phonon model (QPM) with inclusion of the Coriolis coupling, reasonably well reproduce octupole correlations in this nucleus. © The Author(s), 2016, This work was supported in part by the Swedish Natural Science Research Council, Norwegian Scientific Research Committee, the Nansen Foundation, the CICYT “Plan Nacional de Altas Energias” Spain (under contract AEN94-0833-C02-02), the U.K. Engineering and Physical Sciences Research Council, and the Polish Scientific Research Committee.

Several new subnanosecond lifetimes were measured in Pd-109 using the fast-timing beta gamma gamma (t) method. Fission fragments of the A = 109 mass chain were produced by bombarding natural uranium with 30 MeV protons at the Jyvaskyla Ion Guide Isotope Separator On-Line (IGISOL) facility. Lifetimes were obtained for excited states in Pd-109 populated following beta decay of Rh-109. The new lifetimes provide some insight into the evolution of nuclear structure in this mass region. In particular, the distinct structure of the two low-lying 7/2(+) states occurring systematically across the Pd isotopic chain is supported by the new lifetime measurements. The available nuclear data indicate a sudden increase in deformation at N = 60 which is related to the strong p-n interaction between pi g(9/2) and vg(7/2) valence nucleons expected in this region.

Properties of excited states in Nd-147 have been studied with the multispectra and gamma gamma coincidencemeasurements. Twenty-four new gamma lines and three new levels have been introduced into the level scheme of Nd-147. Using the advanced time-delayed beta gamma gamma(t) method, we measured lifetimes of eight excited levels in Nd-147, populated via the beta decay of Pr-147. We have determined reduced transition probabilities for 30 gamma transitions. Multidimensional potential energy surface calculations performed for Nd-147 suggest two single-quasiparticle configurations with nonzero octupole deformation, with K = 1/2 and K = 5/2. Our calculations also predict a sizable value of the electric dipole moment vertical bar D-0 vertical bar = 0.26e fm for this nucleus, while experimentally, a lower limit of vertical bar D-0 vertical bar >= 0.02e fm has been evaluated for the supposed K = 1/2 parity doublet. In contrast to the theoretical results, we do not observe the parity doublet bands with K = 5/2. This, and the lack of theoretically expected E1 strength in Nd-147,Nd-149 may signal some poorly understood structural effect in the odd-N lanthanides.

Isotopes of francium have been produced via a spallation reaction of thorium carbide and separated in the ISOCELE facility. The very weak beta branch (0.35%) of 220Fr decay and the beta decay of 222Fr leading to the levels of 220Ra and 222Ra, respectively, have been studied by means of gamma -ray singles and beta -gated gamma - gamma coincidence measurements. A strong evidence has been obtained for the 1- state in 220Ra at 412.9 keV and 15 new levels have been added to the eight excited states known previously in 222Ra. The 3- to 2+ E1 transition in the latter nucleus has been found to be remarkably enhanced compared with analogous transitions in the heavier radium isotopes. This enhancement together with the low energy of the 1- state reflects octupole instability of 222Ra. The essentially higher energy of the 1- state in 220Ra suggests that the latter nucleus already lies at the border of the octupole instability region. In contradiction to experimental indications the theory places 220Ra inside this region. For 222Ra it predicts a Q1 value not far from the authors' experimental result but fails to reproduce Q1, changes in 224,226,228Ra nuclei.

The beta decay of 215Bi and 216Bi isotopes has been studied by mass separation and nuclear spectroscopy methods using spallation reactions on thorium carbide. For the 7.7+or-0.2 min 215Bi activity the beta decay has been found to populate six of the 215Po levels known previously from the alpha decay of 219Rn. The 216Bi activity has been identified through its beta decay to 216Po, to the 550 keV level known already from the alpha decay of 220Rn and to a new level at 969 keV. Its half-life has been determined to be 3.6+or-0.4 min.

4 pages, 3 figures, 1 table.-- PACS nrs.: 21.10.Tg; 23.40.−s; 27.40.+z., The Advanced-Time-Delayed method was used to measure lifetimes of the states in Ar-41 populated in the β decay of Cl-41. The nuclei Cl-41 were produced at ISOLDE by 1.4-GeV proton bombardment of a thick UCx target and mass-separated as molecular ions, XeCl+. Our measured half-life of the 167.1-keV state, T(1/2) = 315(15) ps, is significantly lower than the previously measured value of 410(30) ps. We have also determined T(1/2) = 260(80) ps and T(1/2) ≤ 46 ps for the 515.9- and 1867.7-keV states, respectively. These are the shortest lifetimes measured so far with the ultrafast timing method using the new LaBr3(Ce) crystals for γ-ray detection., This work was performed as part of an undergraduate research project (ERW) at the Physics Department of the University of Notre Dame. Fast-timing detectors and electronics were provided by the Fast Timing Pool of Electronics. This study was supported in part by the NSF PHY04-57120, Swedish Research Council, BMBF Grant No. 06KY205I, the Alexander von Humboldt Foundation (WBW), Foundation for Polish Science (AK), the European Union Sixth Framework through RII3-EURONS (Contract No. 506065), and the EURTD project TARGISOL (HPRI-CT-2001-50033).

The results of the Doppler-shift attenuation method lifetime measurements in partner bands of 128 Cs and 132 La are presented. Experimental reduced transition probabilities in 128 Cs are compared with theoretical calculations done in the frame of the core-quasiparticle coupling model. The electromagnetic properties, energy and spin of levels belonging to the partner bands show that 128 Cs is the best known example revealing the chiral symmetry breaking phenomenon.

Lifetimes of excited states in {sup 229}Th, populated in the {beta} decay of {sup 229}Ac, have been measured using the advanced time-delayed {beta}{gamma}{gamma}(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new {gamma} lines have been introduced into the {beta}-decay scheme of {sup 229}Ac based on results of {gamma}{gamma} coincidence measurements. Reduced transition probabilities have been determined for more than 70 {gamma} transitions in {sup 229}Th. Average |D{sub 0}| values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K{sup {pi}}=1/2{sup {+-}},3/2{sup {+-}}, and 5/2{sup {+-}} parity partner bands, respectively. Excited states in {sup 229}Th and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2{sup +} isomeric state is predicted to be about 10 h. Potential energy surfaces on the ({beta}{sub 2},{beta}{sub 3}) plane for the lowest single quasiparticle configurations in {sup 229}Th have been calculated using the Strutinsky method.

A new isotope 220At has been identified among the mass-separated products of a spallation reaction of ThO2. Its half-life has been found to be 3.71+or-0.04 min. This isotope was identified through its beta decay to four excited levels in 220Rn known previously from the alpha decay of 224Ra.

The γ-rays following the β − decay of 230 Fr have been investigated by means of γ-ray singles including multispectrum analysis and γγ coincidence measurements using Ge(Li) detectors. The half-life of 230 Fr was measured to be 19.1 ± 0.5 s. Most of the observed transitions could be placed in a level scheme comprising 23 new excited states of 230 Ra, ten of them grouped into the K π = 0 + ground-state band, the K π = 0 − band with its 1 − state at 710.9 keV and a K π = 2 + γ-vibrational band with its head at 734.8 keV. It is concluded that 230 Ra is a better rotator than the lighter radium isotopes, and has no ground-state octupole deformation.