Browsing by Author "K.S. Golda"

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Asymmetric fission around lead: The case of Po 198
(American Physical Society, 2019) Shilpi Gupta; C. Schmitt; K. Mahata; A. Shrivastava; P. Sugathan; A. Jhingan; K.S. Golda; N. Saneesh; M. Kumar; G. Kaur; L. Stuttgé; D. Arora; H. Arora; A. Chatterjee; K. Chauhan; S.K. Duggi; D.P. Kaur; V. Mishra; Prashant N. Patil; K. Rani
Asymmetric low-energy fission of neutron-deficient nuclei around lead is addressed with the measurement of fragment mass and total kinetic energy properties for the fissioning system Po198 produced in heavy-ion fusion. Interpretation of the measurement for such a transitional nucleus at finite excitation energy is challenging. The presence of asymmetric partitions is suggested by the observed weak dependence of the total kinetic energy on mass and by the nonmonotonic evolution of the fragment-mass distribution width with excitation energy. The interpretation is supported by microscopic model calculations as well as by the results of an advanced semiempirical code. Combined with previous experiments in the region, the present measurement contributes to establish the evolution of the fragment-mass distribution as a function of the fissioning system. The connection between the "new" and the "old" islands of asymmetric fission is discussed. © 2019 American Physical Society.
Erratum to "Pre-compound neutron evaporation in low energy heavy ion fusion reactions" [Nucl. Phys. A 798 (2008) 1-15] (DOI:10.1016/j.nuclphysa.2007.10.007)
(2009) Ajay Kumar; Hardev Singh; Rajesh Kumar; Gulzar Singh; I.M. Govil; R.P. Singh; Rakesh Kumar; B.K. Yogi; K.S. Golda; S.K. Datta; G. Viesti
[No abstract available]
Erratum: Loss of collectivity in 79Rb (European Physical Journal A (2006) 28 (277-281) DOI:10.1140/epja/i2005-10286-8)
(2006) R.K. Sinha; A. Dhal; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; K.S. Thind; A.K. Sinha; I.M. Govil; R.K. Bhowmik; J.B. Gupta; P.K. Joshi; A.K. Jain; S.C. Pancholi; L. Chaturvedi
[No abstract available]
Fission dynamics and entrance-channel study in the Po 210 compound nucleus via light-particle multiplicities
(American Physical Society, 2023) Chetan Sharma; B.R. Behera; Shruti; Amit; Bharti Rohila; Amninderjeet Kaur; Subodh; Neha Dhanda; Ashok Kumar; P. Sugathan; A. Jhingan; K.S. Golda; N. Saneesh; Mohit Kumar; H. Arora; Divya Arora; H.P. Sharma
Neutron multiplicities, folding angle distribution, mass distribution, and mass-energy distribution are measured for the compound nucleus Po210 populated through the C12+Pt198 reaction at an excitation energy of 61.6 MeV. The measured neutron multiplicities are compared with the statistical model code joanne2 to extract total fission time for the Po210 compound nucleus. The total fission time (τtot) obtained for this system is (10±5)×10-21 s at 49 MeV and increases to (23±5)×10-21 at 61.8 MeV excitation energy indicating that dissipation increases with excitation energy. A comparison with τtot of the O18+Os192 reaction populating the same compound nucleus indicates the influence of entrance channel mass asymmetry on the fission time. Dynamical model calculations have been performed to understand the fusion dynamics for these reactions and it is observed that the formation time of the compound nucleus increases as we go from the asymmetric to the symmetric entrance channels. Also, these calculations predict that 93% of the total angular momentum lead to the formation of a fully equilibrated compound nucleus for the C12+Pt198 reaction whereas this percentage decreases to 84%, for the O18+Os192 reaction indicating a higher percentage of noncompound nuclear processes in the latter case. © 2023 American Physical Society.
Indian National Gamma Array at Inter University Accelerator Centre, New Delhi
(2010) S. Muralithar; K. Rani; R. Kumar; R.P. Singh; J.J. Das; J. Gehlot; K.S. Golda; A. Jhingan; N. Madhavan; S. Nath; P. Sugathan; T. Varughese; M. Archunan; P. Barua; A. Gupta; M. Jain; A. Kothari; B.P.A. Kumar; A.J. Malyadri; U.G. Naik; Raj Kumar; Rajesh Kumar; J. Zacharias; S. Rao; S.K. Saini; S.K. Suman; M. Kumar; E.T. Subramaniam; S. Venkataramanan; A. Dhal; G. Jnaneswari; D. Negi; M.K. Raju; T. Trivedi; R.K. Bhowmik
A 4π multi-detector gamma-ray spectrometer named the Indian National Gamma Array (INGA) has been set up at the Inter University Accelerator Centre, New Delhi, for nuclear structure studies. The array is designed to incorporate twenty four Compton-suppressed Clover germanium detectors with a total photopeak efficiency ∼5%. The spectrometer along with sub-systems developed in-house like, mechanical support structure, high voltage power supplies, automatic liquid nitrogen filling system, front-end electronics and data acquisition system are described. The mechanical support structure facilitates the use of the Clover Germanium array with a recoil mass separator. The array has been used in a number of nuclear spectroscopic investigations. The in-beam and off-beam performance of the array are reported. © 2010 Elsevier B.V.
Indian National Gamma Array at IUAC
(Institute of Physics Publishing, 2011) S. Muralithar; K. Rani; R.P. Singh; R. Kumar; J.J. Das; J. Gehlot; K.S. Golda; A. Jhingan; N. Madhavan; S. Nath; P. Sugathan; T. Varughese; M. Archunan; P. Barua; A. Gupta; M. Jain; A. Kothari; B.P.A. Kumar; A.J. Malyadri; U.G. Naik; Raj Kumar; Rajesh Kumar; J. Zacharias; S. Rao; S.K. Saini; S.K. Suman; M. Kumar; E.T. Subramaniam; S. Venkataramanan; A. Dhal; G. Jnaneswari; D. Negi; M.K. Raju; T. Trivedi; R.K. Bhowmik
Indian National Gamma Array (INGA) is a 4π multi-detector gamma-ray spectrometer based on twenty four Compton-suppressed Clover Germanium detectors with a total photo peak efficiency ∼ 5 %. INGA was designed to perform high resolution gamma-ray spectroscopy to study nuclear structure at high spins with stable ion beams at Inter University Accelerator Centre (IUAC). Description of the facility and performance of the array are presented in this paper. Since its commissioning, a number of nuclear spectroscopic investigations have been carried out using the array.
Inference on fission timescale from neutron multiplicity measurement in 18O + 184W
(IOP Publishing Ltd, 2022) N.K. Rai; A. Gandhi; M T Senthil Kannan; S.K. Roy; N. Saneesh; M. Kumar; G. Kaur; D. Arora; K.S. Golda; A. Jhingan; P. Sugathan; T.K. Ghosh; Jhilam Sadhukhan; B.K. Nayak; Nabendu K Deb; Saumyajit Biswas; A. Chakraborty; A. Parihari; Ajay Kumar
The pre-scission and post-scission neutron multiplicities are measured for the 18O + 184W reaction in the excitation energy range of 67.23-76.37 MeV. Langevin dynamical calculations are performed to infer the energy dependence of fission decay time in compliance with the measured neutron multiplicities. Different models for nuclear dissipation are employed for this purpose. Fission process is usually expected to be faster at a higher beam energy. However, we found an enhancement in the average fission time as the incident beam energy increases. It happens because a higher excitation energy helps more neutrons to evaporate that eventually stabilizes the system against fission. The competition between fission and neutron evaporation delicately depends on the available excitation energy and it is explained here with the help of the partial fission yields contributed by the different isotopes of the primary compound nucleus. © 2022 IOP Publishing Ltd.
Level density parameter: A tool to study the particle spectra
(2010) Ajay Kumar; A. Kumar; G. Singh; Hardev Singh; R.P. Singh; Rakesh Kumar; K.S. Golda; I.M. Govil
The compound nucleus76Kr*is formed in the heavy-ion fusion reactions by an asymmetric entrance channel 12C+64Zn and the symmetric entrance channel 31P+45Sc at theexcitation energy of 75 MeV and angular momentum of 39 η. Neutron energy spectra of the asymmetric system (12C+64Zn) at different angles are well described by the statistical model predictions using the normal value of the level density parameter a = A/8 MeV-1. However,in the case of the symmetric system (31P+45Sc), the statistical model interpretation of the data requires the change in the value of a = A/10 MeV -1. The delayed evolution of thecompound system in case of the symmetric 31P+45Sc system may lead to the formation of a temperature equilibrated dinuclear complex, which may be responsible for the neutron emission at higher temperature, while the protons and alpha particles are evaporated afterneutron emission when the system is sufficiently cooled down and the higher λ-values do not contribute in the formation of the compound nucleus for the symmetric entrance channel in case of charged particle emission. © 2010 American Institute of Physics.
Loss of collectivity in 79Rb
(Springer New York, 2006) R.K. Sinha; A. Dhal; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; K.S. Thind; A.K. Sinha; I.M. Govil; R.K. Bhowmik; J.B. Gupta; P.K. Joshi; A.K. Jain; S.C. Pancholi; L. Chaturvedi
High-spin states in 79Rb were populated in the reaction 63Cu(19F, p2n) 79Rb at E(beam) = 60 MeV. The lifetimes of the excited states of the πg9/2 positive-parity yrast band and of the πp3/2 negative-parity band in 79Rb were measured by the Doppler Shift Attenuation Method. The deduced transition quadrupole moments Qt are found to have a decreasing trend with rotational frequency for both the bands, consistent with those found experimentally in neighbouring nuclei.
Measurement of neutron multiplicity to investigate the role of entrance channel parameters on the nuclear dissipation
(American Physical Society, 2019) N.K. Rai; A. Gandhi; Ajay Kumar; N. Saneesh; M. Kumar; G. Kaur; A. Parihari; D. Arora; K.S. Golda; A. Jhingan; P. Sugathan; T.K. Ghosh; Jhilam Sadhukhan; B.K. Nayak; Nabendu K. Deb; S. Biswas; A. Chakraborty
In the present work, the pre- and post-scission neutron multiplicities were measured for the reaction O18+W186 at different excitation energies populating the compound nucleus Pb204, using the National Array of Neutron Detectors (NAND) facility at IUAC, New Delhi, India. Here, we investigated the entrance channel effect on the nuclear dissipation involved in the heavy ion fusion-fission dynamics. The statistical model analysis was performed using the code vecstat. The prescribed reaction O18+W186 had similar value of the mass asymmetry as the system O16+Ta181 studied earlier, populating the compound nucleus Tl197. Specifically, we observed the similar behavior from both the systems against the nuclear dissipation, with the similar value of the mass asymmetry. The role of the entrance channel parameters on the nuclear dissipation was also discussed in the present work. © 2019 American Physical Society.
Pre-compound neutron evaporation in low energy heavy ion fusion reactions
(Elsevier, 2008) Ajay Kumar; Hardev Singh; Rajesh Kumar; I.M. Govil; R.P. Singh; Rakesh Kumar; B.K. Yogi; K.S. Golda; S.K. Datta; G. Viesti
Inclusive and exclusive neutron evaporation spectra have been studied from the fusion reactions at 80 MeV 12C on 46Ti and 131 MeV 31P on 27Al, populating the compound nucleus 58Ni at the excitation energy of 79.5 MeV but in different angular momentum ranges. The evaporation residues 53Fe, 55Fe and 56Co were identified by their characteristic γ-rays. The measured energy spectra of evaporated neutrons were compared with the predictions from statistical-model calculations. In case of the asymmetric system 12C + 46Ti, the neutron spectra are well reproduced, when compared with the results from statistical-model calculations with level density parameter a = A / 8 MeV-1. On the contrary, the experimental spectra for the symmetric system 31P + 27Al are found to be harder than the theoretical predictions with a = A / 8 MeV-1. In this case, a lower value of the level density parameter a = A / 10 MeV-1 seems to be required to reproduce the experimental results. The dependence of the energy spectra on the entrance channel is taken as an indication that, in case of the symmetric system, the neutrons are in part emitted from a temperature equilibrated di-nuclear complex at a higher temperature before the formation of the compound nucleus. © 2007 Elsevier B.V. All rights reserved.
Quasielastic scattering measurements in the Si 28 + Nd 142,150 systems
(American Physical Society, 2020) Saumyajit Biswas; A. Chakraborty; A. Jhingan; D. Arora; B.R. Behera; Rohan Biswas; Nabendu Kumar Deb; S.S. Ghugre; Pankaj K. Giri; K.S. Golda; G. Kaur; A. Kumar; M. Kumar; B. Mukherjee; B.K. Nayak; A. Parihari; N.K. Rai; S. Rai; R. Raut; Rudra N. Sahoo; A.K. Sinha
Barrier distributions for the Si28+Nd142,150 systems were extracted from large-angle quasielastic scattering measurements. The measurements were carried out over a wide range of incident beam energies around the Coulomb barriers. The experimental results were compared with the predictions from coupled-channels calculations carried out using different coupling schemes. Reasonable agreement between the experimental and theoretical results was obtained. The role of coupling effects of the various excitation modes of the projectile and target on the observed barrier distributions is discussed. The sensitivity of the quasielastic scattering process on the mode of projectile excitation is clearly been seen from the use of two different types of targets, Nd142 and Nd150, having spherical and deformed shapes at the ground state, respectively. © 2020 American Physical Society.
Role of nuclear dissipation and entrance channel mass asymmetry in pre-scission neutron multiplicity enhancement in fusion-fission reactions
(American Physical Society, 2008) Hardev Singh; K.S. Golda; Santanu Pal; Ranjeet; Rohit Sandal; Bivash R. Behera; Gulzar Singh; Akhil Jhingan; R.P. Singh; P. Sugathan; M.B. Chatterjee; S.K. Datta; Ajay Kumar; G. Viesti; I.M. Govil
Pre-scission neutron multiplicities are measured for 12C+204Pb and 19F+197Au reactions at laboratory energies of 75-95 MeV for the C12 beam and 98-118 MeV for the F19 beam. The chosen projectile-target combinations in the present study lie on either side of the Businaro-Gallone mass asymmetry (αBG) and populate the Ra216 compound nucleus. The dissipation strength is deduced after comparing the experimentally measured neutron yield with the statistical model predictions which contains the nuclear viscosity as a free parameter. Present results demonstrate the combined effects of entrance channel mass asymmetry and the dissipative property of nuclear matter on the pre-scission neutron multiplicity in fusion-fission reactions. © 2008 The American Physical Society.
Shape changes at high spin in 78Kr
(2006) A. Dhal; R.K. Sinha; P. Agarwal; S. Kumar; Monika; B.B. Singh; R. Kumar; P. Bringel; A. Neusser; R. Kumar; K.S. Golda; R.P. Singh; S. Muralithar; N. Madhavan; J.J. Das; A. Shukla; P.K. Raina; K.S. Thind; A.K. Sinha; I.M. Govil; P.K. Joshi; R.K. Bhowmik; A.K. Jain; S.C. Pancholi; L. Chaturvedi
High-spin states in 78Kr have been studied via the 63Cu (19F, 2p2n)78Kr reaction at a beam energy of 60 MeV using the Indian National Gamma Array (INGA). In this nucleus, lifetimes have been measured upto the I π=22+ level in the yrast positive-parity band and upto the I π=15- level in the negative-parity band using the Doppler Shift Attenuation Method (DSAM). The deduced transition quadrupole moments Qt's are found to decrease with rotational frequency for both the bands.
Study of angular momentum hindrance in heavy ion fusion reactions
(EDP Sciences, 2015) Ajay Kumar; A. Kumar; B.R. Behra; Hardev Singh; R.P. Singh; R. Kumar; K.S. Golda
The systematic study of the properties of hot nuclei by detecting the emitted charged particles and neutrons in coincidence with residual nuclei provides very critical information about its nuclear level density. These emitted particles capable to explain the behavior of the nucleus at various stages of the de-excitation cascade process. So, we have studied, a set of four compound nuclei, which were populated by mass-symmetric and mass-asymmetric channels, leading to the same compound nuclei, namely 80Sr∗, 79Se∗, 76Kr∗ and 58Ni∗at same excitation energies, respectively and found that the experimental neutron and charged particle spectra for symmetric channel show deviations at higher energies in comparison to the statistical model calculations. © Owned by the authors, published by EDP Sciences, 2014.
Study of nuclear reaction dynamics through particle evaporation
(2013) Ajay Kumar; A. Kumar; G. Singh; Hardev Singh; R.P. Singh; Rakesh Kumar; K.S. Golda; I.M. Govil
The compound nucleus 76Kr* is formed in the heavy-ion fusion reactions by an asymmetric entrance channel 12C+ 64Zn and the symmetric entrance channel 31P+ 45Sc at the excitation energy of 75 MeV and angular momentum of 39 ℏ. Neutron energy spectra of the asymmetric system (12C+ 64Zn) at different angles are well described by the statistical model predictions using the normal value of the level density parameter a = A/8 MeV -1. However, in the case of the symmetric system ( 31P+45Sc), the statistical model interpretation of the data requires the change in the value of a = A/10 MeV-1. The delayed evolution of the compound system in case of the symmetric 31P+ 45Sc system may lead to the formation of a temperature equilibrated dinuclear complex, which may be responsible for the neutron emission at higher temperature, while the protons and alpha particles are evaporated after neutron emission when the system is sufficiently cooled down and the higher ℓ-values do not contribute in the formation of the compound nucleus for the symmetric entrance channel in case of charged particle emission. © 2013 AIP Publishing LLC.