The new isotopes, 235Bk and its <italic>&#945;</italic>-decay daughter 231Am, were investigated using the gas-filled recoil separator SHANS2. They were identified by measuring radioactive decay chains originating from 235Bk, which was produced via the 197Au( 40Ar, 2n) 235Bk reaction. Three correlated <italic>&#945;</italic>-decay chains were assigned to 235Bk, from which the <italic>&#945;</italic>-particle energy of 235Bk was measured to be 7632(17) keV. For 231Am, the <italic>&#945;</italic>-particle energy and half-life were determined to be 7109(18) keV and <math altimg='si5.svg'><msubsup><mn>75</mn><mrow><mo>&#8722;</mo><mn>30</mn></mrow><mrow><mo>+</mo><mn>137</mn></mrow></msubsup></math> s, respectively. The <italic>&#945;</italic>-decay branching ratio of 231Am was evaluated as <math altimg='si6.svg'><mrow><msubsup><mn>17</mn><mrow><mo>&#8722;</mo><mn>15</mn></mrow><mrow><mo>+</mo><mn>65</mn></mrow></msubsup><mo>%</mo></mrow></math>. A systematic analysis reveals significant discrepancies between the experimental data and the WS4+RBF theoretical predictions for the isotopes of Bk and Am, which warrant further investigation.

China

J.G. Wang

Z.C. Li

Z.Y. Zhang

Z.G. Gan

United Kingdom

Japan

A.N. Andreyev

M.H. Huang

L. Ma

M.M. Zhang

H.B. Yang

C.L. Yang

Y.H. Qiang

Z.H. Li

X.Y. Huang

G. Xie

L. Zhu

H. Zhou

X. Zhang

J.H. Zheng

S.Y. Xu

Z. Zhao

L.C. Sun

F. Guan

X.L. Wu

W.X. Huang

Y.L. Tian

Y.S. Wang

J.Y. Wang

Z.W. Lu

Y. He

L.T. Sun

Z.Z. Ren

S.G. Zhou

Russia

V.K. Utyonkov

A.A. Voinov

Yu.S. Tsyganov

A.N. Polyakov

Decay properties of new isotopes 235Bk and 231Am

The nuclear properties of bismuth isotopes <math altimg='si12.svg'><mrow><mo>(</mo><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>83</mn><mo>)</mo></mrow></math>, with just one valence proton above the closed spherical shell at <math altimg='si13.svg'><mrow><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>82</mn></mrow></math>, are expected to be governed by a single unpaired proton. However, already in semimagic 209Bi <math altimg='si14.svg'><mrow><mo>(</mo><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>83</mn></mrow></math>, <math altimg='si15.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>126</mn><mo>)</mo></mrow></math>, the magnetic moment ( <italic>&#956;</italic>) strongly deviates from the single-particle Schmidt value. A near linear decrease in <italic>&#956;</italic> with the increase of <italic>N</italic> after the <math altimg='si4.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>126</mn></mrow></math> magic number was observed up to <math altimg='si16.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>130</mn></mrow></math>. In order to test whether this trend is kept at <italic>N</italic>&#8239;&gt;&#8239;130 and to reveal the underlying mechanisms, an investigation of 215,217Bi <math altimg='si17.svg'><mrow><mo>(</mo><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>132</mn><mo>,</mo><mn>134</mn><mo>)</mo></mrow></math> has been undertaken. The magnetic dipole and electric quadrupole moments of the <math altimg='si5.svg'><mrow><msup><mi>I</mi><mi>&#960;</mi></msup><mo linebreak='goodbreak'>=</mo><mn>9</mn><mo linebreak='goodbreak'>/</mo><msup><mn>2</mn><mo>&#8722;</mo></msup></mrow></math> nuclear ground states in these isotopes have been measured for the first time using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). It has been shown that the linearly decreasing trend of <italic>&#956;</italic>( 209,211,213Bi <italic>g</italic>) is broken in 215,217Bi with a nearly constant value of <italic>&#956;</italic> observed. Experimental data have been compared to calculations in the framework of the configuration-interaction shell model with the monopole-based universal V <inf>MU</inf>+LS interaction. The peculiarities in the behavior of <italic>&#956;</italic>(Bi, <math altimg='si18.svg'><mrow><mn>9</mn><mo linebreak='goodbreak'>/</mo><msup><mn>2</mn><mo>&#8722;</mo></msup></mrow></math>) with increasing neutron number are explained as being due to the shell evolution, change of the neutron orbitals occupancies and strong configuration mixing beyond <math altimg='si16.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>130</mn></mrow></math>. Also, the difference in the <italic>&#956;</italic> trends for bismuth <math altimg='si12.svg'><mrow><mo>(</mo><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>83</mn><mo>)</mo></mrow></math> and astatine <math altimg='si19.svg'><mrow><mo>(</mo><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>85</mn><mo>)</mo></mrow></math> isotopes with <italic>N</italic>&#8239;&gt;&#8239;126 are reproduced by the shell-model calculations. It is shown that monopole interaction plays noticeable role in the description of the peculiarities of the <italic>&#956;</italic> behaviour. Additionally, the extension of the application of the V <inf>MU</inf> interaction to the <italic>&#956;</italic> isotopic trends for heavy nuclei is important for further study of the capabilities of this promising version of the shell-model calculations.

A. Barzakh

M.D. Seliverstov

Z. Yue

Menglan Liu

Cenxi Yuan

Spain

Hungary

A. Algora

Slovakia

B. Andel

S. Antalic

Oman

M. Al Monthery

Germany

Switzerland

D. Atanasov

J. Benito

Italy

G. Benzoni

T. Berry

M.L. Bissell

K. Blaum

M.J.G. Borge

K. Chrysalidis

Romania

C. Clisu

Belgium

T.E. Cocolios

C. Costache

J.G. Cubiss

Canada

T. Day Goodacre

G.J. Farooq-Smith

D.V. Fedorov

V.N. Fedosseev

L.M. Fraile

Denmark

H.O.U. Fynbo

V. Gadelshin

L.P. Gaffney

United States

R. F Garcia Ruiz

C. Granados

Finland

P.T. Greenlees

R.D. Harding

L.J. Harkness-Brennan

R. Heinke

A. Herlert

M. Huyse

A. Illana

J. Jolie

D.S. Judson

Sweden

J. Karls

J. Konki

P. Larmonier

I. Lazarus

D. Leimbach

R. Lică

Z. Liu

France

D. Lunney

K.M. Lynch

M. Madurga

V. Manea

N. Marginean

R. Marginean

B.A. Marsh

C. Mihai

P. Molkanov

P. Mosat

M. Mougeot

J.R. Murias

E. Nacher

A. Negret

D. Neidherr

L. Nies

R.D. Page

S. Pascu

A. Perea

V. Pucknell

P. Rahkila

C. Raison

E. Rapisarda

K. Rezynkina

M. Rosenbush

R.E. Rossel

S. Rothe

V. Sánchez-Tembleque

K. Schomacker

L. Schweikhard

C. Seiffert

S. Sels

C. Sotty

L. Stan

M. Stryjczyk

D. Studer

J. Sundberg

C. Sürder

O. Tengblad

P. Van Duppen

V. Vedia

M. Verlinde

S. Viñals

N. Warr

A. Welker

F. Wienholtz

Australia

R.N. Wolf

Electromagnetic moments of 215,217Bi: Probing shell evolution beyond <math altimg='si4.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>126</mn></mrow></math>

Near the doubly-magic nucleus 78Ni ( <math altimg='si1.svg'><mi>Z</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>28</mn></math>, <math altimg='si2.svg'><mi>N</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>50</mn></math>), there has been a decades-long debate on the existence of a long-lived isomer in 76Cu. A recent mass measurement claimed to have settled the debate, by measuring the energy of the isomer and shedding light on the structure of the nucleus. In this work, we present new, more accurate, and precise values of the half-lives of the isomeric and ground states in 76Cu. Our findings suggest that both states have very similar half-lives, in the 600&#8211;700 ms range, in disagreement with the literature values, implying that they cannot be differentiated by their decay curves. These results raise more questions than they answer, reopening the debate and showing that the structures in 76Cu are still not fully understood.

B. Olaizola

D.P. Suárez-Bustamante

G. Del Piccolo

Poland

M. Araszkiewicz

Y. Ayyad

South Africa

R.A. Bark

Z. Favier

F. Galtarossa

G. Georgiev

P.T. Greenless

R. Grzywacz

P. Ibañez

K. Johnston

P.M. Jones

A. Korgul

U. Köster

J. Kurcewicz

M. Labiche

M. Llanos-Expósito

Czechia

R.E. Mihai

E. Nácher

C. Neacsu

V.M. Nouvilas

J. Ojala

J.N. Orce

C.A.A. Page

J. Pakarinen

J. Papadakis

M. Piersa-Siłkowska

A.M. Plaza

Zs. Podolyák

W. Poklepa

F. Rotaru

M. Siciliano

J.M. Udías

R. Wadsworth

H. De Witte

D. Yates

The 76Cu conundrum remains unsolved

The magnetic dipole moments (μ) of $^{209}$Tl$^{g}$ (<math><mi>N</mi><mo>=</mo><mn>128</mn></math>) and $^{207}$Tl$^{m}$ (<math><mi>N</mi><mo>=</mo><mn>126</mn></math>) have been measured for the first time using the in-source laser resonance-ionization spectroscopy technique with the Laser Ion Source and Trap (LIST) at ISOLDE (CERN). The application of the LIST suppresses the usually overwhelming background of the isobaric francium isotopes and allows access to heavy thallium isotopes with <math><mi>A</mi><mo>⩾</mo><mn>207</mn></math>. The self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. well describes the N dependence of μ for <math><mn>1</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math> thallium ground states, as well as μ for the <math><mn>11</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup></math> isomeric states in europium, gold and thallium isotopes. The inclusion of particle-vibration coupling leads to a better agreement between the theory and experiment for μ(Tl$^{g}$, <math><msup><mrow><mi>I</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mn>1</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math>). It is shown that beyond mean-field contributions to μ cannot be neglected at least for thallium isotopes with <math><msup><mrow><mi>I</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mn>1</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math>.

CERN

A.E. Barzakh

I.N. Borzov

Magnetic moments of thallium isotopes in the vicinity of magic = 126