The structure of the <math altimg='si35.svg'><msubsup><mrow /><mn>22</mn><mn>43</mn></msubsup></math>Ti <inf>21</inf> nucleus has been explored employing correlations between delayed and prompt <italic>&#947;</italic> rays, leading to a substantial extension of its positive-parity yrast band up to 25/2 <math altimg='si36.svg'><msup><mrow /><mo>+</mo></msup></math>. New states were were identified using the isomer-tagging technique together with <math altimg='si37.svg'><mrow><mi>&#947;</mi><mspace width='0.16em' /><mo linebreak='goodbreak'>&#8722;</mo><mspace width='0.16em' /><mi>&#947;</mi></mrow></math> coincidences and were compared to the analogue states in the mirror nucleus <math altimg='si38.svg'><msubsup><mrow /><mn>21</mn><mn>43</mn></msubsup></math>Sc <inf>22</inf>. The Mirror Energy Differences (MED) between analogue states have been extracted and compared to the predictions from the Large-Scale Shell-Model calculations in two main shells. For the positive-parity states which involve particle-hole excitations from the <italic>sd</italic> to the <italic>fp</italic> shell, a striking correlation between the measured MED and the type of nucleons excited across the shell gap is observed. This is reinforced by the systematic behavior of non-natural parity MED for nuclei across the entire <italic>f</italic> <inf>7/2</inf> shell, which puts in evidence that experimental MED serve as direct, sensitive probes of the underlying microscopic structure of nuclear wave function.

Italy

K. Rezynkina

Finland

A. Illana Sison

S.M. Lenzi

F. Recchia

P. Ruotsalainen

P. Aguilera

K. Auranen

J. Benito

S. Carollo

M.L. Cortes

R. Escudeiro

T. Grahn

P.T. Greenlees

South Korea

J. Ha

R. Julin

H. Joukainen

H. Jutila

M. Leino

J. Louko

M. Luoma

D. Napoli

J. Ojala

J. Pakarinen

S. Pigliapoco

Spain

A. Poves

P. Rahkila

M. Sandzelius

J. Sarén

A. Tolosa-Delgado

J. Uusitalo

United States

G.L. Zimba

Mirror energy differences between 43Ti and 43Sc: A direct insight into the nuclear wave functions

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.

United Kingdom

A.N. Andreyev

A. Barzakh

M.D. Seliverstov

Z. Yue

China

Menglan Liu

Cenxi Yuan

Hungary

A. Algora

Slovakia

B. Andel

S. Antalic

Oman

M. Al Monthery

Germany

Switzerland

D. Atanasov

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

R. F Garcia Ruiz

C. Granados

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

C. Raison

E. Rapisarda

Japan

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>

Competing structures in neutron-deficient even-even lead isotopes have been extensively studied, with low-lying excited states assigned with different shapes. However, the structural properties of the odd-mass lead isotopes remain comparatively less explored. Here, we report on the first lifetime measurement of low-lying yrast states above the <math altimg='si10.svg'><mrow><mn>13</mn><mo linebreak='goodbreak'>/</mo><msubsup><mn>2</mn><mn>1</mn><mo>+</mo></msubsup></mrow></math> state in <math altimg='si4.svg'><msup><mrow /><mn>191</mn></msup></math>Pb, and the first direct in-beam measurement of internal conversion-electron branches between <math altimg='si58.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>J</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math> states in <math altimg='si6.svg'><msup><mrow /><mn>189</mn></msup></math>Pb. These experiments were conducted at the University of Jyv&#228;skyl&#228; using the <small-caps>appa</small-caps> and <small-caps>sage</small-caps> setups at the <small-caps>ritu</small-caps> and <small-caps>mara</small-caps> separators, respectively. Contrary to earlier interpretations, we propose that these low-lying yrast states in <math altimg='si4.svg'><msup><mrow /><mn>191</mn></msup></math>Pb and <math altimg='si6.svg'><msup><mrow /><mn>189</mn></msup></math>Pb nuclei arise from the coupling of an unpaired neutron in the <math altimg='si59.svg'><msub><mi>i</mi><mrow><mn>13</mn><mo>/</mo><mn>2</mn></mrow></msub></math> orbital to the members of the oblate band based on the first excited proton <math altimg='si60.svg'><mrow><mo>(</mo><mn>2</mn><mi>p</mi><mo linebreak='goodbreak'>&#8722;</mo><mn>2</mn><mi>h</mi><mo>)</mo></mrow></math> intruder <math altimg='si61.svg'><msup><mn>0</mn><mo>+</mo></msup></math> states in <math altimg='si62.svg'><msup><mrow /><mn>192</mn></msup></math>Pb and <math altimg='si8.svg'><msup><mrow /><mn>190</mn></msup></math>Pb nuclei, respectively. This interpretation is supported by the measured lifetimes in <math altimg='si4.svg'><msup><mrow /><mn>191</mn></msup></math>Pb, which yield an average transition quadrupole moment of <math altimg='si63.svg'><mrow><mrow><mo stretchy='false'>|</mo></mrow><msub><mi>Q</mi><mi>t</mi></msub><mrow><mo>|</mo><mo>=</mo><mn>4.81</mn><mrow><mo>(</mo><mn>16</mn><mo>)</mo></mrow></mrow></mrow></math> eb comparable to predominantly oblate bands in the region. Additional support comes from the particle-core coupling scheme observed in <math altimg='si6.svg'><msup><mrow /><mn>189</mn></msup></math>Pb. Our results confirm the triple shape-coexistence in <math altimg='si6.svg'><msup><mrow /><mn>189</mn></msup></math>Pb, provide new insights into the evolution of nuclear shapes in neutron-deficient lead isotopes and establish a benchmark for future theoretical models.

A.M. Plaza

P. Papadakis

R.D. Herzberg

A.D. Briscoe

E. Uusikylä

Saudi Arabia

B. Alayed

A. Alharbi

O. Alonso-Sañudo

V. Bogdanoff

J. Chadderton

A. Esmaylzadeh

C. Fransen

C. Lakenbrink

A. McCarter

B.S. Nara Singh

A. Raggio

J. Romero

M.M. Satrazani

C.M. Sullivan

Á. Tolosa-Delgado

F. von Spee

J. Warbinek

Shape coexistence and particle-core coupling in <math altimg='si6.svg'><msup><mrow /><mn>189</mn></msup></math>Pb and <math altimg='si4.svg'><msup><mrow /><mn>191</mn></msup></math>Pb nuclei

Proton-neutron configurations in atomic nuclei can manifest in a variety of different structures, and exotic nuclei provide fruitful ground for exploring their relation to fundamental symmetries. Here, we report on in-beam <italic>&#947;</italic>-ray spectroscopy of the very neutron-deficient 184Pb nucleus using the <small-caps>jurogam II</small-caps> spectrometer at the <small-caps>ritu</small-caps> separator in a recoil-decay tagging experiment. For the first time, transitions from the non-yrast states have been observed in a Pb nucleus beyond the neutron <math altimg='si1.svg'><mi>N</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>104</mn></math> midshell. In comparison to neighboring Pb isotopes and theoretical models, de-excitation patterns from these states are similar to those associated with predominantly oblate shapes in heavier Pb isotopes. Together with the known predominantly prolate yrast band and the spherical ground state, this suggests that triple-shape coexistence prevails in the 184Pb nucleus.

R. Wadsworth

H. Badran

D.M. Cox

A. Brown

T. Calverley

J. Hilton

R. Llewellyn

S. Juutinen

J. Partanen

C. Scholey

S. Stoltze

B. Wallis

Competing structures in the beyond neutron N=104 midshell nucleus 184Pb

Competing configurations, assigned with three different shapes, are mixed at low angular momentum in the neutron-deficient $^{188}$Pb nucleus. Here, we present a simultaneous conversion electron and γ-ray in-beam spectroscopic precision measurement employing the sage spectrometer. The level energy of the first excited state, <math><msubsup><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math>, has been determined at 591(1)keV through direct measurement of conversion electrons. By using the intensity of the observed <math><msubsup><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo>→</mo><msubsup><mrow><mn>0</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> transition to the ground state, the feeding of the <math><msubsup><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> state has been determined for the first time, which suggests the <math><msubsup><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> state is the head of the predominantly prolate band. The compositions of the <math><msubsup><mrow><mn>4</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo>→</mo><msubsup><mrow><mn>4</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> and <math><msubsup><mrow><mn>2</mn></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mo>→</mo><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math> inter-band transitions have been determined, indicating configuration mixing between the bands.

Poland

K. Hadyńska-Klek

A. Herzáň

U. Jakobsson

A. Mistry

D. O'Donnell

P. Peura

J. Sorri

K. Wrzosek-Lipska

Direct observation of 0 Transitions in Pb through in-beam spectroscopy

We present the first experimental evidence of the scissors mode in the superheavy nucleus 254No produced in the 208Pb( 48Ca, <math altimg='si1.svg'><mn>2</mn><mi>n</mi><mi>&#947;</mi></math>)) 254No reaction. The spectrum of <italic>&#947;</italic> rays emitted by the excited 254No nuclei shows an enhanced <italic>&#947;</italic>-ray yield for transition energies of &#8776;2.5 MeV. By measuring the linear polarization properties of the emitted <italic>&#947;</italic> rays, we confirm that the transitions in the enhancement region are predominantly of magnetic-dipole character, characteristic for the scissors mode. To further characterize the enhanced <italic>&#947;</italic>-ray yield, simulations of the electromagnetic decay of 254No were performed. The observed enhancement is reproduced by including an <italic>M</italic>1 component in the <italic>&#947;</italic> strength function with total strength <math altimg='si2.svg'><mi>B</mi><mo stretchy='false'>(</mo><mi>M</mi><mn>1</mn><mo stretchy='false'>&#8593;</mo><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>11.8</mn><mo stretchy='false'>(</mo><mn>19</mn><mo stretchy='false'>)</mo><mspace width='0.25em' /><msubsup><mrow><mi>&#956;</mi></mrow><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msubsup></math>. This is in good agreement with the integrated <italic>M</italic>1 strength from sum-rule estimates and new calculations within the quasi-particle random-phase approximation presented here. Our results provide a stringent test of phenomenological formulae for the scissors mode currently used in stellar nucleosynthesis calculations. We find that those formulae are not satisfactory, and we recommend using sum-rule estimates assuming a rigid-body moment of inertia instead for describing the scissors mode in superheavy nuclei.

Norway

F.L. Bello Garrote

A. Lopez-Martens

A.C. Larsen

Experimental observation of the <italic>M</italic>1 scissors mode in 254No