The lifetimes of low-lying excited states below the <math altimg='si1.svg'><msup><mrow><mn>8</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msup></math> seniority isomer were directly measured using fast timing detectors in the neutron-deficient isotopes 98,100Cd. This experiment was conducted with the DEcay SPECtroscopy (DESPEC) setup at GSI, where the ions of interest were produced via a fragmentation reaction and identified using the FRagment Separator (FRS) before being implanted in the AIDA active stopper system, and the <italic>&#947;</italic> rays emitted during the de-excitation of isomeric states were detected by the LaBr <inf>3</inf> FATIMA Array. The newly deduced values for the reduced transition probabilities were compared with shell-model calculations using different interactions and effective charges. The results indicate that, while 98Cd aligns well with a seniority scheme description, in 100Cd the transition strengths among low-lying states are not fully reproduced, and the nature of these states remains an open problem within the present theoretical description. Ultimately, a key element in the description of this region, crucial for nuclear physics and astrophysics, appears to be the proton-neutron term of the nuclear effective interaction.

China

Italy

G. Zhang

M. Polettini

D. Mengoni

G. Benzoni

Z. Huang

Germany

M. Górska

A. Blazhev

Spain

L.M. Fraile

A. Gargano

G. De Gregorio

France

F. Nowacki

G. Aggez

U. Ahmed

Sweden

O. Aktas

Saudi Arabia

M. Al-Aqeel

United Kingdom

B. Alayed

H.M. Albers

A. Algora

S. Alhomaidhi

F. Amjad

C. Appleton

T. Arıcı

M. Armstrong

B.Q. Arnés

A. Astier

M. Balogh

A. Banerjee

D. Bazzacco

J. Benito Garcìa

S. Bottoni

P. Boutachkov

A. Bracco

A. Bruce

D. Brugnara

C. Bruno

F. Camera

B. Cederwall

M. Cicerchia

M.M.R. Chishti

A. Corsi

M.L. Cortes

D. Cox

F.C.L. Crespi

B. Das

T. Davidson

G. de Angelis

T. Dickel

M. Doncel

A. Ertoprak

A. Esmaylzadeh

L. Gaffney

F. Galtarossa

E.R. Gamba

J. Garbe

D. Genna

J. Gerl

A. Goasduff

A. Gottardo

A. Gozzelino

Finland

T. Grahn

J. Ha

E. Haettner

O. Hall

L. Harkness-Brennan

H. Heggen

C. Hornung

Y. Hrabar

S.P. Hu

N. Hubbard

K.E. Ide

A. Illana

S. Jazrawi

P.R. John

J. Jolie

C. Jones

D. Joss

D. Judson

V. Karayonchev

E. Kazantseva

R. Kern

Hungary

G.G. Kiss

L. Knafla

R. Knöbel

I. Kojouharov

Poland

A. Korgul

W. Korten

P. Koseoglou

D. Kostyleva

T. Kurtukian-Nieto

Slovenia

G. Kosir

N. Kurz

I. Kuti

M. Labiche

S.M. Lenzi

S. Leoni

G.S. Li

Z. Liu

M. Llanos Expósito

R. Lozeva

J.B. Lu

Approaching 100Sn: Structural evolution in 98,100Cd via lifetime measurements

Similar to short-range correlated electron pairs under the constraint of long-range Coulomb interaction, which describe condensed atomic states, isoscalar <math altimg='si1.svg'><mo stretchy='false'>(</mo><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>0</mn><mo stretchy='false'>)</mo></math> and isovector <math altimg='si2.svg'><mo stretchy='false'>(</mo><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>1</mn><mo stretchy='false'>)</mo></math> <italic>pn</italic> correlations, including short-range pairing and long-range non-pairing components, are respectively exclusive for nuclei in the vicinity of the <math altimg='si3.svg'><mi>N</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi>Z</mi></math> line. In the framework of spherical shell model, these are found to be connected by two angle dependent control parameters <math altimg='si4.svg'><mfrac><mrow><msup><mrow><mi mathvariant='normal'>cos</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&#8289;</mo><msub><mrow><mi>&#952;</mi></mrow><mrow><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>0</mn></mrow></msub></mrow><mrow><msup><mrow><mi mathvariant='normal'>cos</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&#8289;</mo><msub><mrow><mi>&#952;</mi></mrow><mrow><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>1</mn></mrow></msub></mrow></mfrac></math> and <math altimg='si5.svg'><mfrac><mrow><msup><mrow><mi mathvariant='normal'>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&#8289;</mo><msub><mrow><mi>&#952;</mi></mrow><mrow><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>0</mn></mrow></msub></mrow><mrow><msup><mrow><mi mathvariant='normal'>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&#8289;</mo><msub><mrow><mi>&#952;</mi></mrow><mrow><mi>T</mi><mo linebreak='badbreak' linebreakstyle='after'>=</mo><mn>1</mn></mrow></msub></mrow></mfrac></math> of <math altimg='si6.svg'><mi>U</mi><mo stretchy='false'>(</mo><mn>1</mn><mo stretchy='false'>)</mo></math> gauge symmetry breaking in the <math altimg='si7.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn><mo stretchy='false'>&#8594;</mo><mn>0</mn></math> quantum phase transition. The former, which serves as the relative amplitude, reveals a complex mixing between spin singlet ( <math altimg='si8.svg'><mi>S</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>) or <math altimg='si9.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math> and triplet ( <math altimg='si10.svg'><mi>S</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math>) or <math altimg='si11.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math> <italic>pn</italic> pairing phases. The long-standing elusiveness of <math altimg='si11.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math> pairing phase is here explained by not only the quenching of <math altimg='si11.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math> pairing correlation but also the less prominent pairing element among strong <math altimg='si11.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math> interactions on average, while the appearance of <math altimg='si9.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math> <italic>pn</italic> pairing phase is naturally related to the enhancement and prominence of <math altimg='si9.svg'><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math> pairing interaction.

F.F. Zeng

K.K. Zheng

M.L. Liu

H.L. Wang

Relative amplitude in the mixed-spin <italic>pn</italic> superfluid phase

Excited states have been observed for the first time in the very neutron-deficient odd-odd nucleus <math><msubsup><mrow></mrow><mrow><mspace width="0.25em"></mspace><mn>57</mn></mrow><mrow><mn>120</mn></mrow></msubsup></math>La$_{63}$. The observed γ rays have been assigned based on coincidences with lanthanum X rays measured with the JUROGAM 3 array and with <math><mi>A</mi><mo>=</mo><mn>120</mn></math> fusion-evaporation residues measured with the MARA separator. The observed γ rays form a rotational band which decays to the ground state via a cascade of four low-energy transitions. Based on the systematic comparisons with the heavier odd-odd La isotopes we assign spin-parity <math><msup><mrow><mn>4</mn></mrow><mrow><mo>+</mo></mrow></msup></math> to the ground state and a <math><mi>π</mi><msub><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>⊗</mo><mi>ν</mi><msub><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub></math> configuration to the rotational band. The nuclear shape has been investigated by the cranked Nilsson-Strutinsky model. Two quasiparticle plus triaxial rotor model calculations including the np interaction nicely reproduce the spin of the inversion between the even- and odd-spin cascades of E2 transitions, giving credit to the np interaction as an important parameter responsible for the mechanism inducing the inversion. The position of the Fermi levels, in particular for neutrons, also has a strong impact on the observed inversion in the chain of lanthanum nuclei.

P.M. Jodidar

C.M. Petrache

B.F. Lv

South Africa

E.A. Lawrie

S. Guo

K. Auranen

A.D. Briscoe

P.T. Greenlees

H. Joukainen

R. Julin

J. Louko

M. Luoma

H. Jutila

J. Ojala

J. Pakarinen

A.M. Plaza

P. Rahkila

P. Ruotsalainen

J. Sarén

A. Tolosa-Delgado

J. Uusitalo

G. Zimba

A. Krakó

Canada

C. Andreoiu

D.T. Joss

R.D. Page

E.A. Cederlöf

First observation of excited states in La and its impact on the shape evolution in the ≈ 120 Mass Region

Starting from a <math><mo>|</mo><mi>ϕ</mi><msup><mrow><mo>|</mo></mrow><mrow><mn>4</mn></mrow></msup></math> field theory with universal pn interacting angular and distance coordinates <math><mo>(</mo><mi>θ</mi><mo>,</mo><mi>r</mi><mo>)</mo></math> to depict nuclear long-range correlations, we have derived a cubic Schrödinger equation for <math><msub><mrow><mi>N</mi></mrow><mrow><mi>p</mi></mrow></msub><msub><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow></msub></math> pn interacting virtual bosons, which are believed to dominate the generic evolution of nuclear structure from spherical multi-nucleon shell-model states to deformed collective rotational states. It is shown that two-soliton solution in θ space manifests two opposite pn-type Ising-like chains existing in ground states and their gradual alignment responsible for nuclear rotational excitations. Of particular prominence is two-soliton solution with respect to r: the mutual relative motion of valence protons and neutrons around valence-nucleon mass centers considered as the dynamic equilibrium positions of a non-linear Schrödinger breather. And the resulting non-vanishing root mean square <math><msqrt><mrow><mo>〈</mo><msup><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>〉</mo></mrow></msqrt></math> divides half the valence nucleons belonging to a chain into four local mass centers and proposes two chain-corresponding molecule-like tetrads outside inert cores pairwise hidden in ground states. Such solitons turn out to be an analogue of opposite axion fluids around a local mass center in the galactic dark-matter halo outside the soliton core (Garnier et al. (2021) [67]) and the present study facilitates making the latter more clear. The generalized molecule-like structure arouses a requisite to the addition of cluster-interior and cluster-to-core electric dipole moments in particular to pear-shaped nuclei, whose variants Schiff moments play an important role in measuring diamagnetic atomic electric dipole moments and therefore understanding CP-violating new physics beyond the standard model. We put additional parts in evidence by befitting the <math><msub><mrow><mi>N</mi></mrow><mrow><mi>p</mi></mrow></msub><msub><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow></msub></math> scheme verified already by electric quadrupole moments in same nuclei.

Generalized molecule-like structure in atomic nuclei

The electromagnetic character of the <math><mi>Δ</mi><mi>I</mi><mo>=</mo><mn>1</mn></math> transitions connecting the 1- to 0-phonon and the 2- to 1-phonon wobbling bands should be dominated by an E2 component, due to the collective motion of the entire nuclear charge. In the present work it is shown, based on combined angular correlation and linear polarization measurements, that the mixing ratios of all analyzed connecting transitions between low-lying bands in $^{135}$Pr interpreted as 0-, 1-, and 2-phonon wobbling bands, have absolute values smaller than one. This indicates predominant M1 magnetic character, which is incompatible with the proposed wobbling nature. All experimental observables are instead in good agreement with quasiparticle-plus-triaxial-rotor model calculations, which describe the bands as resulting from a rapid re-alignment of the total angular momentum from the short to the intermediate nuclear axis.

H.J. Ong

J.G. Wang

X.H. Zhou

Z.Y. Sun

H. Badran

T. Calverley

D.M. Cox

J. Hilton

S. Juutinen

CERN

J. Konki

P. Papadakis

J. Partanen

M. Sandzelius

C. Scholey

J. Sorri

United States

S. Stolze

H. Liu

J. Timár

A. Tucholski

J. Srebrny

Evidence against the wobbling nature of low-spin bands in Pr

Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-rich <math><mi>A</mi><mo>≈</mo><mn>120</mn></math> nuclei is reported for the first time. One of the four reported bands in $^{119}$Cs, built on a <math><mn>11</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup></math> state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupled <math><mi>π</mi><msub><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>[</mo><mn>505</mn><mo>]</mo><mn>11</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup></math> configuration associated with oblate shape. Together with the decoupled <math><mi>π</mi><msub><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>[</mo><mn>541</mn><mo>]</mo><mn>3</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup></math> band built on the <math><mn>11</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup></math> prolate state at 110 keV, for which a half-life of <math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>=</mo><mn>55</mn><mo>(</mo><mn>5</mn><mo>)</mo><mspace width="0.25em"></mspace><mrow><mi>μ</mi><mtext>s</mtext></mrow></math> has been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformed <math><mi>A</mi><mo>≈</mo><mn>120</mn></math> nuclei, a phenomenon predicted since long time, but not yet observed. Calculations using the particle-number conserving cranked shell model and two dimensional tilted axis cranking covariant density functional theory support and well reproduce the observed oblate and prolate coexisting low-energy states in $^{119}$Cs.

Z.H. Zhang

P.W. Zhao

Y.K. Wang

H. Tann

Ö. Aktas

W. Zhang

B.M. Nyakó

D. Sohler

Evidence of oblate-prolate shape coexistence in the strongly-deformed nucleus Cs

Several new bands have been identified in $^{130}$Ba, among which there is one with band-head spin <math><msup><mrow><mn>8</mn></mrow><mrow><mo>+</mo></mrow></msup></math>. Its properties are in agreement with the Fermi-aligned <math><mi>ν</mi><msubsup><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow><mrow><mn>2</mn></mrow></msubsup></math>, <math><mn>7</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup><mo>[</mo><mn>523</mn><mo>]</mo><mo>⊗</mo><mn>9</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup><mo>[</mo><mn>514</mn><mo>]</mo></math> Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the <math><mi>A</mi><mo>=</mo><mn>130</mn></math> mass region. The t-band is fed by a dipole band involving two additional <math><msub><mrow><mi>h</mi></mrow><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub></math> protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, total Routhians surfaces (TRS), tilted axis cranking (TAC), particle rotor model (PRM) and projected shell model (PSM), which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, $^{130}$Ba presents one of the best and most complete sets of collective excitations that a γ-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the <math><mi>A</mi><mo>=</mo><mn>130</mn></math> mass region.

P.M. Walker

Q.B. Chen

S. Frauendorf

Y.X. Liu

R.A. Wyss

Y.H. Qiang

E. Dupont

R. Li

A. Boso

F. Recchia

D. Testov

G. Jaworski

D.R. Napoli

Diversity of shapes and rotations in the -soft Ba nucleus: First observation of a -band in the = 130 Mass Region