A Magnetic Rotational (MR) band in 57Fe nucleus has been newly identified and established from the decreasing behaviour of the experimental electric dipole transition probabilities, B(M1), determined from the measured lifetimes of the states. This becomes the first nucleus in the lighter mass ( <math altimg='si1.svg'><mi>A</mi><mo linebreak='goodbreak' linebreakstyle='after'>&lt;</mo><mn>60</mn></math>) region in which, the B(M1) values of an MR band are measured. A single-particle configuration of <math altimg='si2.svg'><mi>&#960;</mi><msubsup><mrow><mi>f</mi></mrow><mrow><mn>7</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn></mrow></msubsup><mo>&#8855;</mo><mi>&#957;</mi><msup><mrow><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub><msub><mrow><mi>f</mi></mrow><mrow><mn>5</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub><mo stretchy='false'>)</mo></mrow><mrow><mn>3</mn></mrow></msup></math> has been assigned to this MR band. This configuration, which involves only the negative parity proton and neutron orbitals below and above the Z,N = 28 shell closures, respectively, is a unique one which was not identified before for an MR band. The range of observed angular momenta for this band is congruent with this configuration and the experimental data are found to be in agreement with the SPAC (Shears mechanism with Principal Axis Cranking) and semi-classical calculations. Shell model calculations with GXPF1A interaction reproduce the observed levels in 57Fe including the band head of the MR band. This validates the assigned configurations of this band.

India

S. Basu

G. Mukherjee

S. Rajbanshi

Japan

Y. Utsuno

Noritaka Shimizu

France

S. Nandi

S.S. Nayak

S. Pal

S. Bhattacharyya

S. Chakraborty

Soumik Bhattacharya

Shabir Dar

Sneha Das

S. Basak

D. Kumar

D. Paul

K. Banerjee

Pratap Roy

S. Manna

Samir Kundu

T.K. Rana

R. Pandey

S. Samanta

S. Chatterjee

R. Raut

S.S. Ghugre

Romania

H. Pai

A. Karmakar

S. Chattopadhyay

S. Das Gupta

P. Pallav

R. Banik

S. Ali

China

Y.M. Wang

Q.B. Chen

Conclusive evidence of magnetic rotational band in 57Fe: Extending the shears mechanism to the fp shell orbital

A positive parity sequence of <math><mi>Δ</mi><mi>I</mi><mo>=</mo><mn>2</mn></math> γ transitions has been identified above <math><msup><mrow><mi>I</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mn>9</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math> state (<math><msub><mrow><mi>E</mi></mrow><mrow><mi>x</mi></mrow></msub><mo>=</mo><mn>2019</mn></math> keV) in $^{115}$Sb through in-beam γ ray spectroscopic technique. Rotational features of this sequence are found similar to a low-K decoupled band. Observation of this newly identified low-K decoupled band, along with the earlier reported strongly coupled high-K band in this nucleus, provides the first experimental evidence for prolate-oblate shape coexistence associated with <math><msub><mrow><mi>g</mi></mrow><mrow><mn>9</mn><mo>/</mo><mn>2</mn></mrow></msub></math> proton-hole configuration around <math><mi>Z</mi><mo>=</mo><mn>50</mn></math> shell closure. Experimental results are reproduced reasonably well in the frameworks of the projected shell model and the total Routhian surface calculations.

S. Jehangir

G.H. Bhat

J.A. Sheikh

N. Rather

C. Bhattacharya

D. Mondal

S. Mukhopadhyay

D. Pandit

Coexistence of low- Oblate and High- Prolate Proton-hole Bands in Sb

We develop a static charged stellar model in f(R, T) gravity where the modification is assumed to be linear in T which is the trace of the energy momentum tensor. The exterior spacetime of the charged object is described by the Reissner–Nordström metric. The interior solution is obtained by invoking the Buchdahl–Vaidya–Tikekar ansatz, for the metric potential $$g_{rr}$$ <math> <msub> <mi>g</mi> <mrow> <mi>rr</mi> </mrow> </msub> </math> , which has a clear geometric interpretation. A detailed physical analysis of the model clearly shows distinct physical features of the resulting stellar configuration under such a modification. We find the maximum compactness bound for such a class of compact stars which is a generalization of the Buchdahl bound for a charged sphere described in f(R, T) gravity. Our result shows physical behaviour that is distinct from general relativity.

Ranjan Sharma

South Africa

Sunil Maharaj

Electromagnetic extension of Buchdahl bound in f(R, T) gravity

Relative isotopic yield distributions have been extracted for nine correlated fission fragment pairs following a detailed analysis of prompt <math><mi>γ</mi><mo>−</mo><mi>γ</mi></math> coincidence events from $^{232}$Th(α,f) reaction at E<math><msub><mrow></mrow><mrow><mi>l</mi><mi>a</mi><mi>b</mi></mrow></msub></math> = 30 MeV. Simultaneously, the charge and mass yield distributions of the even-even fission fragments have been obtained from the measured relative isotopic yields. The onset of a triple-hump structure is seen in the extracted charge as well as mass yield distributions of the fragments. The results are consistent with the two-mode fission hypothesis of compound nucleus and in good agreement with the theoretical predictions, based on relevant fission models. The detailed results provide experimental evidence for the presence of two distinct compound nucleus fission modes, where the asymmetric and symmetric fission components are 83% and 17%, respectively. An average neutron multiplicity value of 4.60 ± 0.09 has been obtained, and the extracted neutron multiplicity distribution pattern corroborates the observed features of the multifaceted fission modes. Comparing the measured yield distributions following the $^{232}$Th(α,f) surrogate reaction, which produces $^{236}$U$^{⁎}$ at an excitation energy of 21.5 MeV, with that of the direct reaction of 14 MeV neutron induced fission of $^{235}$U, an increase of about 11% in the yield of the symmetric component has been observed.

Aniruddha Dey

D.C. Biswas

A. Chakraborty

A.K. Mondal

K. Mandal

B. Mukherjee

R. Chakrabarti

B.N. Joshi

L.A. Kinage

S. Das

A. Goswami

Evidence for competing bi-faceted compound nucleus fission modes in Th( ,f) Reaction

Anisotropy is one factor that appears to be significantly important in the studies of relativistic compact stars. In this paper, we make a generalization of the Buchdahl limit by incorporating an anisotropic effect for a selected class of exact solutions describing anisotropic stellar objects. In the isotropic case of a homogeneous distribution, we regain the Buchdahl limit $$2M/R \le 8/9$$ <math> <mrow> <mn>2</mn> <mi>M</mi> <mo>/</mo> <mi>R</mi> <mo>≤</mo> <mn>8</mn> <mo>/</mo> <mn>9</mn> </mrow> </math> . Our investigation shows a direct link between the maximum allowed compactness and pressure anisotropy vi-a-vis geometry of the associated 3-space.

Arpita Ghosh

Shyam Das

Anisotropic generalization of Buchdahl bound for specific stellar models

An exclusive systematic study of the giant dipole resonance (GDR) parameters has been performed in very light mass nucleus <math><mmultiscripts><mrow><mtext>P</mtext></mrow><mprescripts></mprescripts><none></none><mrow><mn>31</mn></mrow></mmultiscripts></math> in the temperature range of <math><mo>∼</mo><mn>0.8</mn><mtext>–</mtext><mn>2.1</mn><mspace width="0.25em"></mspace><mtext>MeV</mtext></math> and average angular momentum of <math><mo>∼</mo><mn>11</mn><mtext>–</mtext><mn>16</mn><mspace width="0.25em"></mspace><mi>ħ</mi></math>. The high-energy γ rays from the decay of the GDR, evaporated neutrons and γ-ray multiplicities have been measured. The angular distribution of high-energy γ rays has also been measured at <math><msub><mrow><mi>E</mi></mrow><mrow><mi>beam</mi></mrow></msub><mo>=</mo><mn>42</mn><mspace width="0.25em"></mspace><mtext>MeV</mtext></math>. The GDR parameters, nuclear level density parameter and nuclear temperature were precisely determined by simultaneous statistical model analysis of high-energy γ ray and evaporated neutron spectra. It is observed that the measured width remains roughly constant up to a temperature of <math><mo>∼</mo><mn>1.6</mn><mspace width="0.25em"></mspace><mtext>MeV</mtext></math>. Moreover, the thermal pairing plays no role in describing the GDR width in this open-shell light nucleus at the above-mentioned temperatures and angular momenta. The present measurements provide an excellent platform to extend the applicability of the existing theoretical models down to the very light mass nuclei.

Debasish Mondal

Deepak Pandit

Surajit Pal

Srijit Bhattacharya

A. De

Vietnam

N. Dinh Dang

N. Quang Hung

Balaram Dey

S.R. Banerjee

Study of giant dipole resonance in hot rotating light mass nucleus P

The High-spin states in $^{195}$Tl, populated through the $^{185,187}$Re($^{13}$C, xn) fusion evaporation reaction at the beam energy of 75 MeV, were studied using the Indian National Gamma Array (INGA). More than 50 new γ transitions have been placed in the proposed level scheme which is extended up to the excitation energy of ≈ 5.6 MeV and spin<math><mo>=</mo><mn>22.5</mn><mi>ħ</mi></math>. Two pairs of degenerate bands based on two different quasi-particle configurations have been identified in this nucleus indicating the first observation of such bands in an odd-A nucleus in <math><mi>A</mi><mo>∼</mo><mn>190</mn></math> region and signify the first evidence of multiple chiral bands in a nucleus in this region. The total Routhian surface calculations predict triaxial shapes for both the configurations and thereby, support the experimental observation. The importance of multiple neutron holes in the <math><msub><mrow><mi>i</mi></mrow><mrow><mn>13</mn><mo>/</mo><mn>2</mn></mrow></msub></math> orbital and the stability of shapes for these two configurations have been discussed.

T. Roy

Md.A. Asgar

S. Bhattacharya

T.K. Ghosh

Australia

P. Roy

J. Meena

A. Dhal

R. Palit

S. Saha

J. Sethi

Shital Thakur

B.S. Naidu

S.V. Jadav

R. Dhonti

Observation of multiple doubly degenerate bands in Tl

Exclusive measurement of isospin (I) mixing in $^{32}$S at high temperature (T) has been performed utilizing the γ-decay of isovector giant dipole resonance (IVGDR). The degree of isospin mixing was deduced from the ratio of high energy γ-ray cross-sections of $^{32}$S and $^{31}$P populated at the same temperature and angular momentum (J). Precise temperature was determined by simultaneous measurement of nuclear level density (NLD) parameter and angular momentum. The measured Coulomb spreading width (<math><msup><mrow><mi>Γ</mi></mrow><mrow><mo>↓</mo></mrow></msup></math>) seems to be independent of temperature and angular momentum. The isospin becomes a good quantum number with increase in temperature. However, when compared with the calculation at high temperature, measured isospin mixing is underpredicted by the calculations.

Exclusive measurement of isospin mixing at high temperature in S