Proton and α-particle energy spectra were measured in coincidence with fission fragments at different relative angles in $^{16}$O (96 MeV) + $^{232}$Th reaction. The multiplicity spectra were analyzed within the framework of a Moving Source Disentangling Analysis (MSDA) to determine contributions from different emission stages. The MSDA conclusively shows “Near Scission Emission (NSE)” as an essential component in the multiplicity spectra. In contrast to NSE α particles which emit mainly perpendicular (“equatorial emission”), the NSE protons are observed to be emitted perpendicular as well as parallel (“polar emission”) to the fission axis with similar intensities (~20% for each). Thus, around 40% of total pre-scission protons are emitted near the scission stage, whereas the same fraction for α particles is only around 10%. The inevitable presence of “polar” and “equatorial” NSE protons in a heavy-ion induced fission has been observed for the first time. Present results open up a new avenue to study the heavy-ion induced fission dynamics.

India

Pawan Singh

Y.K. Gupta

G.K. Prajapati

B.N. Joshi

V.G. Prajapati

N. Sirswal

K. Ramachandran

A.S. Pradeep

V.S. Dagre

M. Kumar

A. Jhingan

N. Deshmukh

B.V. John

B.K. Nayak

D.C. Biswas

R.K. Choudhury

Observation of near-scission “polar” and “equatorial” proton emission in heavy-ion induced fission

The strength distributions of the Isoscalar Giant Monopole Resonance (ISGMR) and Isoscalar Giant Quadrupole Resonance (ISGQR) in $^{142,146−150}$Nd have been determined via inelastic α-particle scattering with the Grand Raiden (GR) Spectrometer at the Research Center for Nuclear Physics (RCNP), Japan. In the deformed nuclei $^{146−150}$Nd, the ISGMR strength distributions exhibit a splitting into two components, while the nearly spherical nucleus $^{142}$Nd displays a single peak in the ISGMR strength distribution. A noteworthy achievement in this study is the first-time detection of overtones in the Isoscalar Giant Quadrupole Resonance (ISGQR) strength distributions within Nd isotopes at an excitation energy around 25 MeV obtained through Multipole Decomposition Analysis (MDA).

M. Abdullah

S. Bagchi

Netherlands

M.N. Harakeh

Japan

H. Akimune

D. Das

T. Doi

South Africa

L.M. Donaldson

Y. Fujikawa

M. Fujiwara

T. Furuno

United States

U. Garg

K.B. Howard

Y. Hijikata

K. Inaba

S. Ishida

M. Itoh

N. Kalantar-Nayestanaki

D. Kar

T. Kawabata

S. Kawashima

K. Khokhar

K. Kitamura

N. Kobayashi

Y. Matsuda

A. Nakagawa

S. Nakamura

K. Nosaka

S. Okamoto

S. Ota

S. Pal

R. Pramanik

S. Roy

S. Weyhmiller

Z. Yang

J.C. Zamora

Effect of ground-state deformation on the isoscalar giant monopole resonance and the first observation of overtones of the isoscalar giant quadrupole resonance in rare-Earth Nd isotopes

The pre-scission <italic>&#945;</italic>-particle multiplicity ( <math altimg='si1.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mi mathvariant='normal'>pre</mi></mrow></msub></math>), measured in 16O (96 MeV) + 232Th reaction, is observed to be significantly lower than the global trend reported earlier. Statistical model calculations also show a much shorter fission-time to reproduce the experimental <math altimg='si1.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mi mathvariant='normal'>pre</mi></mrow></msub></math>. By assimilating the previous measurements, it is observed that the <math altimg='si1.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mi mathvariant='normal'>pre</mi></mrow></msub></math> makes a changeover from high to a very low value while crossing the Businaro Gallone point in mass asymmetry in the entrance channels in heavy-ion induced fission of 232Th. Similar discontinuous behavior with respect to the entrance channel mass asymmetry was observed earlier in fission fragment angular anisotropy data, and it was attributed to &#8220;pre-equilibrium fission&#8221;. The present results on <math altimg='si1.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mi mathvariant='normal'>pre</mi></mrow></msub></math> provide compelling evidence for an admixture of non-equilibrium fission which depends on the entrance channel dynamics.

L.S. Danu

S. Dubey

S. Mukhopadhyay

N. Kumar

K. Mahata

New signature of non-equilibrium fission from pre-scission <italic>&#945;</italic>-particle emission

Quasi-elastic (QEL) scattering measurements have been performed using a $^{28}$Si projectile off a $^{90}$Zr target at energies around the Coulomb barrier. A Bayesian analysis within the framework of coupled channels (CC) calculations is performed in a large parameter space of quadrupole and hexadecapole deformations (<math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub></math> and <math><msub><mrow><mi>β</mi></mrow><mrow><mn>4</mn></mrow></msub></math>) of $^{28}$Si. Our results unambiguously show that $^{28}$Si is an oblate shaped nucleus with <math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub></math>=-<math><mn>0.38</mn><mo>±</mo><mn>0.01</mn></math> which is in excellent agreement with results from electromagnetic probes. The sign and magnitude of quadrupole deformation along with a precise value of hexadecapole deformation (<math><msub><mrow><mi>β</mi></mrow><mrow><mn>4</mn></mrow></msub></math>=+<math><mn>0.03</mn><mo>±</mo><mn>0.01</mn></math>) of $^{28}$Si have been determined for the first time using QEL scattering. A remarkable agreement is obtained between the experimental and calculated <math><msub><mrow><mi>β</mi></mrow><mrow><mn>4</mn></mrow></msub></math> values of $^{28}$Si based on Skyrme-Hartree-Fock method. The present results demonstrate the strong sensitivity of the quasi-elastic scattering to the sign and magnitude to the ground state deformation parameters, thus affirming its suitability to be used for rare exotic nuclei using low intensity RIBs.

V.B. Katariya

K. Hagino

D. Patel

V. Ranga

A. Pal

V.V. Desai

S. Panwar

R. Sariyal

I. Mazumdar

Precise determination of quadrupole and hexadecapole deformation parameters of the -shell Nucleus, Si

N. Sensharma

S. Zhu

A.D. Ayangeakaa

S. Frauendorf

W. Li

G.H. Bhat

J.A. Sheikh

M.P. Carpenter

Germany

Q.B. Chen

J.L. Cozzi

S.S. Ghugre

D.J. Hartley

R.V.F. Janssens

F.G. Kondev

T.C. McMaken

R. Palit

J. Sethi

D. Seweryniak

R.P. Singh

Corrigendum to “Two-phonon wobbling in Pr” [Phys. Lett. B 792 (2019) 170–174]

Quasi-elastic scattering measurements have been performed using $^{16}$O and $^{24}$Mg projectiles off $^{90}$Zr at energies around the Coulomb barrier. Experimental data have been analyzed in the framework of coupled channels (CC) calculations using the code CCFULL. The quasi-elastic scattering excitation function and derived barrier distribution for $^{16}$O + $^{90}$Zr reaction are well reproduced by the CC calculations using the vibrational coupling strengths for $^{90}$Zr reported in the literature. Using these vibrational coupling strengths, a Bayesian analysis is carried out for $^{24}$Mg + $^{90}$Zr reaction. The <math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub></math> and <math><msub><mrow><mi>β</mi></mrow><mrow><mn>4</mn></mrow></msub></math> values for $^{24}$Mg are determined to be <math><mo>+</mo><mn>0.43</mn><mo>±</mo><mn>0.02</mn></math> and <math><mo>−</mo><mn>0.11</mn><mo>±</mo><mn>0.02</mn></math>, respectively. The <math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub></math> parameter determined in the present work is in good agreement with results obtained using inelastic scattering probes. The hexadecapole deformation of $^{24}$Mg has been measured very precisely for the first time. Present results establish that quasi-elastic scattering could provide a useful probe to determine the ground state deformation of atomic nuclei.

Türkiye

M. Şenyiğit

W.P. Tan

P.D. O'Malley

M. Smith

Ramandeep Gandhi

T. Anderson

R.J. deBoer

B. Frentz

A. Gyurjinyan

O. Hall

M.R. Hall

J. Hu

E. Lamere

Q. Liu

A. Long

W. Lu

S. Lyons

K. Ostdiek

C. Seymour

M. Skulski

B. Vande Kolk

Determination of hexadecapole ( ) Deformation of the Light-mass Nucleus Mg using quasi-elastic scattering measurements

“Why are the tin isotopes soft?” has remained, for the past decade, an open problem in nuclear structure physics: models which reproduce the isoscalar giant monopole resonance (ISGMR) in the “doubly-closed shell” nuclei, $^{90}$Zr and $^{208}$Pb, overestimate the ISGMR energies of the open-shell tin and cadmium nuclei, by as much as 1 MeV. In an effort to shed some light onto this problem, we present results of detailed studies of the ISGMR in the molybdenum nuclei, with the goal of elucidating where–and how–the softness manifests itself between $^{90}$Zr and the cadmium and tin isotopes. The experiment was conducted using the $^{94,96,98,100}$Mo(<math><mi>α</mi><mo>,</mo><msup><mrow><mi>α</mi></mrow><mrow><mo>′</mo></mrow></msup></math>) reaction at <math><msub><mrow><mi>E</mi></mrow><mrow><mi>α</mi></mrow></msub><mo>=</mo><mn>386</mn></math> MeV. A comparison of the results with relativistic, self-consistent Random-Phase Approximation calculations indicates that the ISGMR response begins to show softness in the molybdenum isotopes beginning with <math><mi>A</mi><mo>=</mo><mn>92</mn></math>.

Y. Ishibashi

K. Karasudani

A. Kohda

M. Murata

J. Okamoto

J. Piekarewicz

A. Sakaue

M. Tsumura

Y. Yang

Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A = 90

The second-phonon (<math><msub><mrow><mi>n</mi></mrow><mrow><mi>ω</mi></mrow></msub><mo>=</mo><mn>2</mn></math>) wobbling band has been established in the nucleus $^{135}$Pr. Conclusive evidence for its wobbling nature comes from the <math><mi>Δ</mi><mi>I</mi><mo>=</mo><mn>1</mn></math>, E2 character of the transitions between the new band and the previously identified transverse wobbler band (<math><msub><mrow><mi>n</mi></mrow><mrow><mi>ω</mi></mrow></msub><mo>=</mo><mn>1</mn></math>) in this nucleus. Theoretical calculations in the framework of the quasiparticle triaxial rotor and triaxial projected shell models are found to be in good agreement with the experimental results.

Two-phonon wobbling in Pr

We point out a potential relevance between the Krein–Gupta–Bleuler (KGB) vacuum leading to a fully covariant quantum field theory for gravity in de Sitter (dS) spacetime and the observable smallness of the cosmological constant. This may provide a formulation of linear quantum gravity in a framework amenable to developing a more complete theory determining the value of the cosmological constant.

China

Hamed Pejhan

Kazuharu Bamba

Iran

Mohammad Enayati

Surena Rahbardehghan

A small non-vanishing cosmological constant from the Krein–Gupta–Bleuler vacuum

In the present paper we develop an algorithm for all spherically symmetric anisotropic charged fluid distributions. Considering a new source function ν(r) we find a set of solutions which is physically well behaved and represents compact stellar models. A detailed study specifically shows that the models actually correspond to strange stars in terms of their mass and radius. In this connection we investigate several physical properties like energy conditions, stability, mass–radius ratio, electric charge content, anisotropic nature and surface redshift through graphical plots and mathematical calculations. All the features from these studies are in excellent agreement with the already available evidence in theory as well as observations.

Oman

S.K. Maurya

Saibal Ray

All spherically symmetric charged anisotropic solutions for compact stars