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Isomer spectroscopy of neutron-rich <sup>168</sup>Tb<sub>103</sub>
Gurgi, L.A.,Regan, P.H.,Sö,derströ,m, P.-A.,Watanabe, H.,Walker, P.M.,Podolyá,k, Zs.,Nishimura, S.,Berry, T.A.,Doornenbal, P.,Lorusso, G.,Isobe, T.,Baba, H.,Xu, Z.Y.,Sakurai, H.,Sumikama Elsevier 2017 Radiation physics and chemistry Vol.140 No.-
<P>In-flight fission of a 345 MeV per nucleon U-238 primary beam on a 2 mm thick Be-9 target has been used to produce and study the decays of a range of neutron-rich nuclei centred around the doubly mid-shell nucleus Dy-170 at the RIBF Facility, RIKEN, Japan. The produced secondary fragments of interest were identified event by-event using the BigRIPS separator. The fragments were implanted into the WAS3ABI position sensitive silicon active stopper which allowed pixelated correlations between implants and their subsequent beta-decay. Discrete gamma-ray transitions emitted following decays from either metastable states or excited states populated following beta decay were identified using the 84 coaxial high-purity germanium (HPGe) detectors of the EURICA spectrometer, which was complemented by 18 additional cerium-doped lanthanum bromide (LaBr3) fast-timing scintillation detectors from the FATIMA collaboration. This paper presents the internal decay of a metastable isomeric excited state in the odd-odd nucleus Tb-168, which corresponds to a single proton-neutron hole configuration in the valence maximum nucleus Dy-170. These data represent the first information on excited states in this nucleus, which is the most neutron-rich odd-odd isotope of terbium (Z=65) studied to date. Nilsson configurations associated with an axially symmetric, prolate-deformed nucleus are proposed for the Tb-168 ground state the observed isomeric state by comparison with Blocked BCS-Nilsson calculations.</P>
Taprogge, J.,Jungclaus, A.,Grawe, H.,Nishimura, S.,Xu, Z.Y.,Doornenbal, P.,Lorusso, G.,Ná,cher, E.,Simpson, G.S.,Sö,derströ,m, P.-A.,Sumikama, T.,Baba, H.,Browne, F.,Fukuda, N.,Gernh&aum North-Holland Pub. Co 2014 Physics letters. Section B Vol.738 No.-
<P><B>Abstract</B></P> <P>The decay of an isomeric state in the neutron-rich nucleus <SUP>129</SUP>Cd has been observed via the detection of internal conversion and Compton electrons providing first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a <SUP>238</SUP>U beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of <I>γ</I>-rays and internal conversion electrons, a multipolarity of <I>E</I>3 was tentatively assigned to the isomeric transition. A half-life of <SUB> T 1 / 2 </SUB> = 3.6 ( 2 ) ms was determined for the new state which was assigned a spin of ( 21 / <SUP> 2 + </SUP> ) , based on a comparison to shell model calculations performed using state-of-the-art realistic effective interactions.</P>
Sö,derströ,m, P.-A.,Walker, P.M.,Wu, J.,Liu, H.L.,Regan, P.H.,Watanabe, H.,Doornenbal, P.,Korkulu, Z.,Lee, P.,Liu, J.J.,Lorusso, G.,Nishimura, S.,Phong, V.H.,Sumikama, T.,Xu, F.R.,Yagi, A.,Zha North-Holland Pub. Co 2016 Physics letters. Section B Vol.762 No.-
<P><B>Abstract</B></P> <P>A detailed study of the structure of the doubly mid-shell nucleus Dy 104 1 66 170 has been carried out, following isomeric and <I>β</I> decay. We have measured the yrast band up to the spin-parity <SUP> J π </SUP> = <SUP> 6 + </SUP> state, the K = 2 <I>γ</I>-vibration band up to the <SUP> 5 + </SUP> state, a low-lying negative-parity band based on a <SUP> 2 − </SUP> state that could be a candidate for the lowest energy octupole vibration state within this nucleus, and a candidate for the <SUP> K π </SUP> = <SUP> 6 + </SUP> two quasi-particle isomer. This state was determined to have an excitation energy of 1643.91(23) keV and a half life of 0.99(4) μs, with a reduced hindrance for its decay to the ground-state band an order of magnitude lower than predicted by <SUB> N p </SUB> <SUB> N n </SUB> systematics. This is interpreted as being due to <I>γ</I>-vibrational mixing from a near degeneracy of the isomer and the <SUP> 6 + </SUP> state of the <I>γ</I> band. Furthermore, the parent nucleus <SUP>170</SUP>Tb has been determined to have a half-life of 0.91 ( − 13 + 18 ) s with a possible spin-parity of <SUP> 2 − </SUP> .</P>
Nuclear structure and β -decay schemes for Te nuclides beyond N=82
Moon, B.,Moon, C.-B.,Sö,derströ,m, P.-A.,Odahara, A.,Lozeva, R.,Hong, B.,Browne, F.,Jung, H. S.,Lee, P.,Lee, C. S.,Yagi, A.,Yuan, C.,Nishimura, S.,Doornenbal, P.,Lorusso, G.,Sumikama, T.,Watan American Physical Society 2017 Physical Review C Vol.95 No.4
<P>We study for the first time the internal structure of Te-140 through the beta-delayed gamma-ray spectroscopy of Sb-140. The very neutron-rich Sb-140 nuclei with Z = 51 and N = 89 were produced by the in-flight fission of U-238 beams at the Radioactive Isotope Beam Factory, RIKEN. The half-life and spin-parity of Sb-140 are reported as 173 +/- 12 ms and 3(-), respectively. In addition to the excited states of Te-140 produced by the beta-decay branch, the beta-delayed one-neutron and two-neutron emission branches were also established. By identifying the first 2(+) and 4(+) excited states of Te-140, we found that Te isotopes persist in their vibrator character with E(4(+))/E(2(+)) = 2. We discuss the distinctive features manifest in this region revealed in pairs of isotopes with the same neutron holes and particles with respect to N = 82.</P>
Watanabe, H.,Wang, H.K.,Lorusso, G.,Nishimura, S.,Xu, Z.Y.,Sumikama, T.,Sö,derströ,m, P.-A.,Doornenbal, P.,Browne, F.,Gey, G.,Jung, H.S.,Taprogge, J.,Vajta, Zs.,Wu, J.,Yagi, A.,Baba, H.,Benzon Elsevier 2019 Physics letters: B Vol.792 No.-
<P><B>Abstract</B></P> <P>The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N = 82 neutron shell closure and its influence on the <I>r</I>-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in <SUP>125</SUP>Pd<SUB>79</SUB> and <SUP>127</SUP>Pd<SUB>81</SUB> studied using the EURICA <I>γ</I>-ray spectrometer, following production via in-flight fission of a high-intensity <SUP>238</SUP>U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of ( 23 / <SUP> 2 + </SUP> ) and ( 19 / <SUP> 2 + </SUP> ) in <SUP>125</SUP>Pd and <SUP>127</SUP>Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus <SUP>132</SUP>Sn.</P>
Corté,s, M.L.,Rodriguez, W.,Doornenbal, P.,Obertelli, A.,Holt, J.D.,Lenzi, S.M.,Mené,ndez, J.,Nowacki, F.,Ogata, K.,Poves, A.,Rodrí,guez, T.R.,Schwenk, A.,Simonis, J.,Stroberg, S.R. North-Holland Pub. Co 2020 Physics letters. Section B Vol.800 No.-
<P><B>Abstract</B></P> <P>Excited states in the N = 40 isotone <SUP>62</SUP>Ti were populated via the <SUP>63</SUP>V ( p , 2 p ) <SUP>62</SUP>Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using <I>γ</I>-ray spectroscopy. The energies of the 2 1 + → 0 gs + and 4 1 + → 2 1 + transitions, observed here for the first time, indicate a deformed <SUP>62</SUP>Ti ground state. These energies are increased compared to the neighboring <SUP>64</SUP>Cr and <SUP>66</SUP>Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for <SUP>62</SUP>Ti show a dominant configuration with four neutrons excited across the N = 40 gap. Likewise, they indicate that the N = 40 island of inversion extends down to Z = 20 , disfavoring a possible doubly magic character of the elusive <SUP>60</SUP>Ca.</P>
βdecay of semi-magicCd130: Revision and extension of the level scheme ofIn130
Jungclaus, A.,Grawe, H.,Nishimura, S.,Doornenbal, P.,Lorusso, G.,Simpson, G. S.,Sö,derströ,m, P.-A.,Sumikama, T.,Taprogge, J.,Xu, Z. Y.,Baba, H.,Browne, F.,Fukuda, N.,Gernhä,user, R.,Gey, American Physical Society 2016 Physical Review C Vol.94 No.2
<P>The beta decay of the semi-magic nucleus Cd-130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In-130 and the observation of additional beta feeding to high- lying core-excited states in In-130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N = 50-82 neutron and Z = 28-50 proton shells and the NA-14 interaction, and good agreement is found.</P>
Watanabe, H.,Lorusso, G.,Nishimura, S.,Otsuka, T.,Ogawa, K.,Xu, Z. Y.,Sumikama, T.,Sö,derströ,m, P.-A.,Doornenbal, P.,Li, Z.,Browne, F.,Gey, G.,Jung, H. S.,Taprogge, J.,Vajta, Zs.,Wu, J.,Yagi, American Physical Society 2014 Physical Review Letters Vol.113 No.4
<P>A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in (126)Pd and is proposed to have a spin and parity of 10(+) with a maximally aligned configuration comprising two neutron holes in the 1h(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in (126)Ag. The smaller energy difference between the 10(+) and 7(-) isomers in (126)Pd than in the heavier N=80 isotones can be interpreted as being ascribed to the monopole shift of the 1h(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below (132)Sn are discussed in terms of the central and tensor forces.</P>
Jungclaus, A.,Gargano, A.,Grawe, H.,Taprogge, J.,Nishimura, S.,Doornenbal, P.,Lorusso, G.,Shimizu, Y.,Simpson, G. S.,Sö,derströ,m, P.-A.,Sumikama, T.,Xu, Z. Y.,Baba, H.,Browne, F.,Fukuda, N.,G American Physical Society 2016 Physical Review C Vol.93 No.4
<P>For the first time, the gamma decay of excited states has been observed in a nucleus situated in the quadrant south-east of doubly magic Sn-132, a region in which experimental information so far is limited to ground-state properties. Six gamma rays with energies of 50, 86, 103, 227, 357, and 602 keV were observed following the beta-delayed neutron emission from Cd-133(85), populated in the projectile fission of a U-238 beam at the Radioactive Isotope Beam Factory at RIKEN within the EURICA project. The new experimental information is compared to the results of a modern realistic shell-model calculation, the first one in this region very far from stability, focusing in particular on the pi 0g(9/2)(-1) circle times nu 1f(7/2) particle-hole multiplet in In-132(83). In addition, theoretical estimates based on a scaling of the two-body matrix elements for the pi h(11/2)(-1) circle times nu g(9/2) analog multiplet in Tl-208(127), one major proton and one major neutron shell above, are presented.</P>