Search for elements 119 and 120

Khuyagbaatar, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Asai, Masato; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.

Physical Review C, 102(6), p.064602_1 - 064602_9, 2020/12

https://doi.org/10.1103/PhysRevC.102.064602

A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the Ti+Bk and Ti+Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA. Over four months of irradiation, neither was detected at cross-section sensitivity levels of 65 and 200 fb, respectively. The non-observation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical predictions on the fission-barrier heights of superheavy nuclei in the region of the island of stability.

Investigation of the = 0 selection rule in Gamow-Teller transitions; The -decay of Hg

Berry, T. A.*; Podolyk, Zs.*; Carroll, R. J.*; Lic, R.*; Grawe, H.*; Timofeyuk, N. K.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; et al.

Physics Letters B, 793, p.271 - 275, 2019/06

https://doi.org/10.1016/j.physletb.2019.04.039

Recoil--fission and recoil---fission events observed in the reaction Ca + Am

Forsberg, U.*; Rudolph, D.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Fahlander, C.*; Gates, J. M.*; Golubev, P.*; Gregorich, K. E.*; Gross, C. J.*; et al.

Nuclear Physics A, 953, p.117 - 138, 2016/09

https://doi.org/10.1016/j.nuclphysa.2016.04.025

Alpha-decay chains observed in the element-115 production reactions of Ca + Am were investigated using a new data set consisting of our recently reported data obtained at GSI and previously reported ones at Dubna and LBNL. Short decay chains of recoil--()-fission type, fourteen of which were observed, and some of which were interpreted as the 2-neutron evaporation products Mc, have been reassigned. It is plausible that most of them were assigned to the 3-neutron evaporation products Mc whose decay chain would on the way have branches of EC decays followed by fission.

Ca + Bk fusion reaction leading to element Z = 117; Long-lived -decaying Db and discovery of Lr

Khuyagbaatar, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Asai, Masato; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.

Physical Review Letters, 112(17), p.172501_1 - 172501_5, 2014/05

https://doi.org/10.1103/PhysRevLett.112.172501

The superheavy element with atomic number 117 was produced in the Ca + Bk fusion reaction using the gas-filled recoil separator TASCA at GSI in Germany. This result verified the previous result of the discovery of new element 117 reported by Flerov Laboratory of Nuclear Reactions in Russia, which makes certain the synthesis and discovery of element 117 in human history. On the other hand, the last nucleus in the decay chain from the element 117 was assigned to be the unknown nucleus Lr instead of the previously reported Db, and Db was found to be the -decaying nucleus with very long half-life.

Alpha-photon coincidence spectroscopy along element 115 decay chains

Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.

Acta Physica Polonica B, 45(2), p.263 - 272, 2014/02

https://doi.org/10.5506/APhysPolB.45.263

Produced in the reaction of Ca beam with an Am target, thirty correlated -decay chains were observed. Observed decay chains are consistent with a previously reported decay chain, which confirms the identification of the element 115. In addition, an -photon coincidence measurement was performed, and rays as well as X-ray candidates were observed in this decay chain. The -ray observation in the heaviest region of superheavy nuclei brings a big progress in the superheavy nuclear structure studies.

Resonant X-ray scattering study of NpRhGa and NpCoGa

Detlefs, B.*; Wilkins, S. B.*; Caciuffo, R.*; Paixo, J. A.*; Kaneko, Koji; Honda, Fuminori*; Metoki, Naoto; Bernhoeft, N.*; Rebizant, J.*; Lander, G. H.*

Physical Review B, 77(2), p.024425_1 - 024425_10, 2008/01

https://doi.org/10.1103/PhysRevB.77.024425

We report a resonant X-ray scattering study of the antiferromagnetic neptunium compounds NpCoGa and NpRhGa. Large resonant signals of magnetic dipole character are observed below the Nel temperatures. The signals at the Np edges confirm the behavior determined previously from neutron diffraction. On application of a magnetic field of 9 T along the [010] direction in NpRhGa, we observe a change in the population of different [110]-type domains. We also observe a magnetic dipole signal at the Ga edge, similarly to the reported UGa case, that can be interpreted within a semilocalized model as an orbital polarization of the Ga 4 states induced via strong hybridization with the Np 5 valence band. Quantitative analysis of the signal shows that the Ga dipole on the two different Ga sites follows closely the Np magnetic moment reorientation in NpRhGa. The ratios of the signals on the two inequivalent Ga sites are not the same for the different compounds.

Recent results in fragmentation isomer spectroscopy with rising

Pietri, S.*; Regan, P. H.*; Podolyk, Zs.*; Rudolph, D.*; Steer, S. J.*; Garnsworthy, A. B.*; Werner-Malento, E.*; Hoischen, R.*; Grska, M.*; Gerl, J.*; et al.

Nuclear Instruments and Methods in Physics Research B, 261(1-2), p.1079 - 1083, 2007/08

https://doi.org/10.1016/j.nimb.2007.04.219

The first results from the stopped beam RISING experimental campaign performed at the GSI laboratory in Darmstadt, Germany, are presented. RISING constitutes a major new experimental program in European nuclear structure physics research aimed at using relativistic energy (typically around 1 GeV per nucleon) projectile fragmentation reactions to populate nuclei with highly exotic proton-to-neutron ratios compared to the line of beta stability. In its high-efficiency stopped beam configuration, the RISING -ray spectrometer consists of 105 individual germanium crystals which view a focal plane in which the exotic nuclei are brought to rest. Here, decays from metastable states with half-lives in the nano to milliseconds range can be observed. Results of initial commissioning experiments are also shown and details of the planned future experimental program are given.

Isomer spectroscopy using relativistic projectile fragmentation at the N=Z line for A8090

Regan, P. H.*; Garnsworthy, A. B.*; Pietri, S.*; Caceres, L.*; Grska, M.*; Rudolph, D.*; Podolyk, Zs.*; Steer, S. J.*; Hoischen, R.*; Gerl, J.*; et al.

Nuclear Physics A, 787(1), p.491c - 498c, 2007/05

https://doi.org/10.1016/j.nuclphysa.2006.12.073

Relativistic energy projectile fragmentation of Pb has been used to produce neutron-rich nuclei with N126. The nuclei of interest were studied by detecting delayed rays following the decay of isomeric states. Experimental information on the excited states of the neutron-rich Pt N=126 nucleus, following internal decay of two isomeric states, was obtained for the first time. Raw experimental data and shell-model calculations are presented.

Induced orbital polarization of Ga ligand atoms in UGa (=Ni, Pd, and Pt)

Kuzushita, Kaori*; Ishii, Kenji; Wilkins, S. B.*; Janousova, B.*; Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Kaneko, Koji; Metoki, Naoto; et al.

Physical Review B, 73(10), p.104431_1 - 104431_5, 2006/03

https://doi.org/10.1103/PhysRevB.73.104431

We report a resonant X-ray scattering study of antiferromagnetic uranium compounds UGa (=Ni, Pd, and Pt) at the Ga -edge. A large resonant signal is observed below the Nel temperatures. The azimuth dependence in both - and - polarization channels establishes that the resonant signal has the symmetry of the magnetic dipole. This resonance with the band electrons is interpreted within a semi-localized model as an orbital polarization of the Ga states induced through strong hybridization with U valence level. These results demonstrate that resonant magnetic X-ray scattering at the anions, taken in combination with symmetry arguments, can be used to determine the configuration of the U moments and provide information about the hybridization.

Magnetic structure of NpTGa(T: Fe, Co, Ni)

Honda, Fuminori; Metoki, Naoto; Kaneko, Koji; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji; Shiokawa, Yoshinobu; Onuki, Yoshichika; Colineau, E.*; Bernhoeft, N.*; et al.

Physica B; Condensed Matter, 359-361, p.1147 - 1149, 2005/06

https://doi.org/10.1016/j.physb.2005.01.304

We have succeeded in growing single crystalline samples of NpTGa (T: Fe, Co, Ni). Magnetic structures of these compounds have been studied by neutron diffraction experiment. We summarize the results of the unusual variety of magnetic structure occurred in NpTGa and discuss in terms of electronic structural point of view.