Excited states built upon long-lived high-spin isomers in hard-to-reach neutron-rich Au ( <math altimg='si14.svg'><mrow><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>79</mn></mrow></math>) isotopes were populated using multi-nucleon transfer reactions between 136Xe and 198Pt at 7 MeV/u. These states in <math altimg='si2.svg'><msup><mrow /><mrow><mn>196</mn><mo>,</mo><mspace width='0.16em' /><mn>198</mn><mo>&#8722;</mo><mn>202</mn></mrow></msup></math>Au were identified for the first time using the powerful combination of the VAMOS++ spectrometer, the CATLIFE detection system, and the AGATA <italic>&#947;</italic>-ray tracking array. Their measured energies exhibit remarkable regularity as a function of neutron number and are seen to be inherited from the energies of yrast-band members in the corresponding Hg ( <math altimg='si15.svg'><mrow><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>80</mn></mrow></math>) isotope. Large-scale shell-model calculations reproduce the observed regularity and show that these states arise from the unique-parity orbitals <italic>&#960;</italic>0 <italic>h</italic> <inf>11/2</inf> and <italic>&#957;</italic>0 <italic>i</italic> <inf>13/2</inf> coupled to the Hg core. This regularity is due to the dominant proton configurations of the Hg and Au isotopes, where the level energies are almost independent of different neutron-orbital occupancies. The calculated Au wave functions show significant higher-spin components of the corresponding Hg core, unlike what is expected in the conventional interpretation in terms of the weak-coupling/decoupling limits of the particle-core coupling model.

South Korea

Y. Cho

Y.H. Kim

France

A. Navin

M. Rejmund

A. Lemasson

D. Ramos

E. Clément

J. Dudouet

P. Van Isacker

China

C. Yuan

M. Liu

United Kingdom

A.N. Andreyev

Y. Son

S. Choi

D. Ackermann

Italy

G. de Angelis

S. Bae

India

R. Banik

S. Bhattacharya

S. Bhattacharyya

K. Chae

F. Didierjean

C. Fougères

G. de France

G. Fremont

J. Goupil

G.M. Gu

J. Ha

K.I. Hahn

Japan

Y. Hirayama

S.C. Jeong

D.T. Kattikat Melcom

C.H. Kim

M.J. Kim

S.H. Kim

W. Korten

P. Marini

H. Miyatake

M. Mukai

A. Mukherjee

G. Mukherjee

T. Niwase

T. Otsuka

J. Park

Spain

R.M. Pérez-Vidal

F. Recchia

K. Rezynkina

P. Schury

J.C. Thomas

I. Tsekhanovich

A. Utepov

Y.X. Watanabe

Regularity of core coupled high-spin structure in neutron-rich 196-202Au isotopes approaching N <math altimg='si13.svg'><mrow><mo>=</mo><mn>126</mn></mrow></math>

Nuclear fission produces two excited fragments which fast fly apart. Their properties at scission depend on the dynamics of fission, and rule their return to equilibrium. The present work addresses the excess of <italic>&#947;</italic>-rays with energies between 3 and 8 MeV emitted during the fragment de-excitation, revealed in the 80&#8217;s but hitherto not fully understood. Combining a state-of-the-art heavy-ion spectrometer and an array of novel scintillators, the island of existence of the so-called &#8220; <italic>&#947;</italic>-bump&#8221; is delineated, and its topography mapped as a function of fragment emitter proton and neutron numbers for the first time. Its connection to the Pygmy Dipole Resonance is discussed by means of dedicated fission calculations employing microscopic nuclear level densities and <italic>&#947;</italic> strength functions. Besides giving insight into the post-scission dynamics of the fragments, the present finding would make fission a new probe of soft dipole modes, complementary to the conventional approaches.

N. Kumar

Poland

C. Schmitt

M. Ciemala

A. Maj

S. Brambilla

O. Dorvaux

G. de. France

A. Goasduff

B. Jacquot

S. Kihel

M. Lewitowicz

O. Litaize

I. Matea

S. Péru

D.S. Ahn

P. Bednarczyk

C. Boiano

Romania

C. Borcea

A. Bracco

M. Caamano

S. Calinescu

D. Curien

G. Duchn̂e

Türkiye

S. Erturk

M. Filliger

M. Forge

B. Fornal

B. Gall

United States

I. Harca

D.G. Jenkins

M. Kmiecik

S. Leoni

K. Mazurek

V. Nanal

A. Oberstedt

Belgium

S. Oberstedt

C. Petrone

J. Piot

B. Sowicki

M. Stanoiu

L. Stuttgé

M. Ziȩbliński

First experimental isotopic mapping of the fission “ <italic>&#947;</italic>-bump&#8221; and its connection to the Pygmy dipole resonance

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.

J.G. Wang

Z.C. Li

Z.Y. Zhang

Z.G. Gan

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

Hungary

A. Algora

Slovakia

B. Andel

S. Antalic

Oman

M. Al Monthery

Germany

Switzerland

D. Atanasov

J. Benito

G. Benzoni

T. Berry

M.L. Bissell

K. Blaum

M.J.G. Borge

K. Chrysalidis

C. Clisu

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

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

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>