176Lu is the key nucleus for understanding the evolution of planetary bodies in the solar system, and the temperature and nucleosynthesis of the <italic>s</italic> process, due to its very long terrestrial half-life <italic>T</italic> <inf>1/2</inf>&#8239;&#8776;&#8239;3.7&#8239;&#215;&#8239;10 10 years. The very long half-life is caused by two anomalous first-forbidden transitions from the <math altimg='si2.svg'><msup><mn>7</mn><mo>&#8722;</mo></msup></math> state with extremely large comparative half-life log <italic>ft</italic>&#8239;&#8776;&#8239;19 which have never been appeared in other cases of the existing nuclear databases. We analyze the underlying mechanism and reason for the anomaly in first-forbidden transitions of 176Lu for the first time, which is based on the projected shell model. It is found that the possible <italic>K</italic>-forbidden nature is indispensable for describing the two extremely weak first-forbidden transitions, and the transition strengths are very sensitive to the detailed configuration mixing and <italic>K</italic> mixing in the nuclear wave functions. The half-life of the <math altimg='si2.svg'><msup><mn>7</mn><mo>&#8722;</mo></msup></math> state is calculated to be <italic>T</italic> <inf>1/2</inf>&#8239;&#8776;&#8239;1.95&#8239;&#215;&#8239;10 10 years. The sensitive dependence of the stellar <math altimg='si1.svg'><msup><mi>&#946;</mi><mo>&#8722;</mo></msup></math>-decay rate of 176Lu on <italic>s</italic>-process temperature is discussed as well.

China

Jing-Wen Ran

Long-Jun Wang

Anomaly in first-forbidden transitions of 176Lu

The dineutron as a bound chargeless nucleus of two identical nucleons has been attracting attention for many decades. In addition to the study of the formation of a bound dineutron in the outgoing channel of specific nuclear reactions, cross-section estimates have been gaining interest as research targets. We used a traditional neutron activation technique to irradiate Lu samples followed by measurements of the induced activity with HPGe spectrometer in order to detect gamma-peaks of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu reaction product when this reaction channel is not open for incident neutron energies. Based on two measurements of the instrumental gamma-ray spectra of Lu samples we reliably identified the presence of the 174 gLu isotope in the outgoing channel of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction. Also, the cross-section for this nuclear reaction was obtained and to be equal <math altimg='si1.svg'><mrow><mn>33</mn><mo>.</mo><msubsup><mn>5</mn><mrow><mo>&#8722;</mo><mn>6.7</mn></mrow><mrow><mo>+</mo><mn>7.0</mn></mrow></msubsup></mrow></math> mb. For the first time, the dineutron as a nuclearreaction product was indirectly detected via statistically significant observation of the induced activity of 174 gLu with a corresponding cross-section estimate.

Ukraine

Ihor Kadenko

Hungary

Barna Biró

Mihály Braun

András Fenyvesi

Kateryna Okopna

Nadiia Sakhno

Loránd Zakàny

Formation of bound dineutrons in the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction and its cross-section

We revisit the proton emitter $^{149}$Lu utilizing the recently developed triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). By incorporating the microscopic nuclear structure properties from the TRHBc theory into the WKB approximation, we successfully reproduce the measured proton-emission half-life of $^{149}$Lu within experimental uncertainties. A triaxial ground state characterized by (<math><mi>β</mi><mo>=</mo><mn>0.17</mn><mo>,</mo><mi>γ</mi><mo>=</mo><msup><mrow><mn>31</mn></mrow><mrow><mo>∘</mo></mrow></msup></math>) has been clarified for $^{149}$Lu. The inclusion of triaxiality significantly changes nuclear density distributions and potentials, which results in enhanced binding of both the nuclear system and the proton-emitting orbital. As a result, a slightly extended half-life for the proton emission of $^{149}$Lu is achieved after considering triaxial deformation degrees of freedom. The examination of the dependence of the decay width on triaxial deformation parameters highlights the significance of microscopic description of nuclear deformation beyond the proton dripline.

Qi Lu

Kai-Yuan Zhang

Shi-Sheng Zhang

Triaxial shape of the one-proton emitter Lu

One-proton radioactivity in $^{149}$Lu, the latest identified proton emitter, is studied in the Wentzel-Kramers-Brillouin (WKB) approach with the proton-nucleus potential extracted from the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) for the first time. The predicted half-life turns out to be consistent with the experimental measurement within uncertainties and (almost) independent of the density functionals in the DRHBc theory. Such a microscopic self-consistent calculation reveals that $^{149}$Lu is oblately deformed with a quadrupole deformation <math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>≈</mo><mo>−</mo><mn>0.18</mn></math>, and rules out the possibility of a prolate quadrupole deformation suggested in the nonadiabatic quasiparticle model. We also check the validity of this approach in the description of $^{150,151}$Lu and their isomeric states. The deviations of the predicted half-lives from their experimental counterparts are mostly smaller than those of the theoretical studies without considering deformation effects. Furthermore, we predict $^{148}$Lu to be a more oblately deformed proton-emitter with a longer half-life than that of $^{149}$Lu, which can be checked in the future. Our studies show that the DRHBc + WKB approach provides a new alternative method to evaluate the half-lives of well-deformed proton emitters.

Yang Xiao

Si-Zhe Xu

Ru-You Zheng

Germany

Xiang-Xiang Sun

Li-Sheng Geng

One-proton emission from Lu in the DRHBc+WKB approach

Quantum shell effects drive many aspects of many-body quantal systems and their interactions. Among these are the quasifission reactions that impede the formation of a compound nucleus in superheavy element (SHE) searches. Fragment production in quasifission is influenced by shell effects as a nontrivial manifestation of microscopic dynamics hindering the full equilibration of the composite system to form the compound nucleus. In this Letter, we use the microscopic time-dependent Hartree-Fock (TDHF) theory to study $^{48}$Ca+$^{249}$Bk collisions to investigate the influence of the tensor component of the effective nucleon-nucleon interaction. The results show that the inclusion of the tensor force causes the spherical shell effect to become more prominent, particularly for the neutron number yield whose peak is exactly at magic number <math><mi>N</mi><mo>=</mo><mn>126</mn></math>. This suggests that the tensor force plays a compelling role in the evolution of dynamical shell effects in nuclear reactions, influencing the competition between spherical and deformed shell gaps.

Liang Li

Lu Guo

United States

K. Godbey

A.S. Umar

Impact of tensor force on quantum shell effects in quasifission reactions

The production of new proton-rich nuclei in the vicinity of $^{100}$Sn is investigated via multinucleon transfer reactions within the framework of microscopic time-dependent Hartree-Fock (TDHF) and statistical model GEMINI++. The TDHF+GEMINI method has demonstrated the reliable description in the multinucleon transfer dynamics and the agreement between theoretical results and experimental data is quite satisfactory in the observed transfer reactions. We reveal the production cross sections of proton-rich nuclei in $^{100}$Sn region via multinucleon transfer reactions to be several orders of magnitude higher than those measured via fusion-evaporation and projectile fragmentation experiments. About 19 new proton-rich isotopes with cross sections of larger than 1 nb are predicted to be produced in multinucleon transfer reaction of $^{58}$Ni with $^{112}$Sn. The reaction mechanisms are discussed to lead the experimental production of these previously unreported nuclei. Multinucleon transfer reactions provide a fascinating possibility to reach the proton drip-line in $^{100}$Sn region and beyond.

Zhenji Wu

Zhong Liu

Guangxiong Peng

Production of proton-rich nuclei in the vicinity of Sn via multinucleon transfer reactions

Recently, Guo and Sun derived an identity for factorial Grothendieck polynomials which is a generalization of the one for Schur polynomials by Fehér, Némethi and Rimányi. We analyze the identity from the point of view of quantum integrability, based on the correspondence between the wavefunctions of a five-vertex model and the Grothendieck polynomials. We give another proof using the quantum inverse scattering method. We also apply the same idea and technique to derive an identity for factorial Grothendieck polynomials for rectangular Young diagrams. Combining with the Guo-Sun identity, we get a duality formula. We also discuss a q-deformation of the Guo-Sun identity.

Japan

Kohei Motegi

Integrability approach to Fehér-Némethi-Rimányi-Guo-Sun type identities for factorial Grothendieck polynomials

The tensor force is implemented into the time-dependent Hartree–Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics is systematically investigated for <math><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>40</mn></mrow></mmultiscripts><mo>+</mo><mrow><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>40</mn></mrow></mmultiscripts></mrow></math>, <math><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>40</mn></mrow></mmultiscripts><mo>+</mo><mrow><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>48</mn></mrow></mmultiscripts></mrow></math>, <math><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>48</mn></mrow></mmultiscripts><mo>+</mo><mrow><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>48</mn></mrow></mmultiscripts></mrow></math>, <math><mmultiscripts><mrow><mi>Ca</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>48</mn></mrow></mmultiscripts><mo>+</mo><mrow><mmultiscripts><mrow><mi>Ni</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>56</mn></mrow></mmultiscripts></mrow></math>, and <math><mmultiscripts><mrow><mi>Ni</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>56</mn></mrow></mmultiscripts><mo>+</mo><mrow><mmultiscripts><mrow><mi>Ni</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>56</mn></mrow></mmultiscripts></mrow></math> reactions which vary by the total number of spin-unsaturated magic numbers in target and projectile. A notable effect on fusion barriers and cross sections is observed by the inclusion of tensor force. The origin of this effect is analyzed. The influence of isoscalar and isovector tensor terms is investigated with the TIJ forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions. Our calculations of above-barrier fusion cross sections also show that tensor force does not significantly affect the dynamical dissipation at near-barrier energies.

Australia

Cédric Simenel

Long Shi

Chong Yu

The role of tensor force in heavy-ion fusion dynamics

The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151 m Lu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151 m Lu.

F. Wang

B.H. Sun

United Kingdom

Z. Liu

R.D. Page

Sweden

C. Qi

Finland

C. Scholey

S.F. Ashley

L. Bianco

I.J. Cullen

Austria

I.G. Darby

S. Eeckhaudt

Canada

A.B. Garnsworthy

W. Gelletly

Spain

M.B. Gomez-Hornillos

T. Grahn

P.T. Greenlees

D.G. Jenkins

G.A. Jones

South Africa

P. Jones

D.T. Joss

R. Julin

S. Juutinen

S. Ketelhut

S. Khan

A. Kishada

M. Leino

M. Niikura

Belgium

M. Nyman

J. Pakarinen

S. Pietri

Z. Podolyak

P. Rahkila

S. Rigby

J. Saren

T. Shizuma

J. Sorri

S. Steer

J. Thomson

N.J. Thompson

J. Uusitalo

P.M. Walker

Netherlands

S. Williams

H.F. Zhang

W.Q. Zhang

L.H. Zhu

Spectroscopic factor and proton formation probability for the d 3/2 proton emitter 151 m Lu

Deep inelastic scattering in 154 Sm+ 160 Gd at energies above the Bass barrier is for the first time investigated with two different microscopic dynamics approaches: improved quantum molecular dynamics (ImQMD) model and time dependent Hartree–Fock (TDHF) theory. No fusion is observed from both models. The capture pocket disappears for this reaction due to strong Coulomb repulsion and the contact time of the di-nuclear system formed in head-on collisions is about 700 fm/c at an incident energy of 440 MeV. The isotope distribution of fragments in the deep inelastic scattering process is predicted with the simulations of the latest ImQMD-v2.2 model together with a statistical code (GEMINI) for describing the secondary decay of fragments. More than 40 extremely neutron-rich unmeasured nuclei with 58≤Z≤76 are observed and the production cross sections are at the order of μb to mb. The multi-nucleon transfer reaction of Sm+Gd could be an alternative way to synthesize new neutron-rich lanthanides which are difficult to be produced with traditional fusion reactions or fission of actinides.

Ning Wang

New neutron-rich isotope production in 154 Sm+ 160 Gd