Publications (15)28.26 Total impact
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Article: Electromagnetic transition from the 4$^+$ to 2$^+$ resonance in $^8$Be measured via the radiative capture in $^4$He+$^4$He
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ABSTRACT: An earlier measurement on the 4$^+$ to 2$^+$ radiative transition in $^8$Be provided the first electromagnetic signature of its dumbbell-like shape. However, the large uncertainty in the measured cross section does not allow a stringent test of nuclear structure models. The present paper reports a more elaborate and precise measurement for this transition, via the radiative capture in the $^4$He+$^4$He reaction, improving the accuracy by about a factor of three. The {\it ab initio} calculations of the radiative transition strength with improved three-nucleon forces are also presented. The experimental results are compared with the predictions of the alpha cluster model and {\it ab initio} calculations.05/2013; -
Article: Measurement of the damping of the nuclear shell effect in the doubly magic ^{208}pb region.
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ABSTRACT: The damping of the nuclear shell effect with excitation energy has been measured through an analysis of the neutron spectra following the triton transfer in the ^{7}Li induced reaction on ^{205}Tl. The measured neutron spectra demonstrate the expected large shell correction energy for the nuclei in the vicinity of doubly magic ^{208}Pb and a small value around ^{184}W. A quantitative extraction of the allowed values of the damping parameter γ, along with those for the asymptotic nuclear level density parameter a[over ˜], has been made for the first time.Physical Review Letters 02/2013; 110(6):062501. · 7.37 Impact Factor -
Article: Role of the cluster structure of 7Li in the dynamics of fragment capture
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ABSTRACT: Exclusive measurements of prompt γ-rays from the heavy-residues with various light charged particles in the 7Li + 198Pt system, at an energy near the Coulomb barrier (E/Vb∼1.6) are reported. Recent dynamic classical trajectory calculations, constrained by the measured fusion, α- and t-capture cross-sections have been used to explain the excitation energy dependence of the residue cross-sections. These calculations distinctly illustrate a two-step process, breakup followed by fusion, in case of the capture of t and α clusters; whereas for 6He+p and 5He+d configurations, massive transfer is inferred to be the dominant mechanism. The present work clearly demonstrates the role played by the cluster structures of 7Li in understanding the reaction dynamics at energies around the Coulomb barrier.Physics Letters B 12/2012; · 3.95 Impact Factor -
Article: Inhomogeneous and intrinsic damping of giant dipole resonance in hot rotating nuclei with A ~ 150
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ABSTRACT: High-energy gamma rays in the range of ~4–28 MeV were measured in the reaction 28Si+124Sn at E(28Si) ~ 185 MeV in coincidence with low-energy gamma ray multiplicities and evaporation residues. The centroid energy and width of the giant dipole resonance were extracted for various multiplicity windows from the statistical model analysis. These extracted widths, along with those from an earlier measurement at E(28Si) ~ 149 MeV, show a discrepancy with the results of a calculation under the thermal shape fluctuation model which describes the inhomogeneous damping of the resonance. An empirical form of the temperature and angular momentum dependence of the width, describing the data at both the beam energies, has been derived. The present results suggest that the contributions from both the inhomogeneous damping and the intrinsic collisional damping processes should be included.Journal of Physics G Nuclear and Particle Physics 03/2010; 37(5):055105. · 4.18 Impact Factor -
Article: Broad structures in γ-ray multiplicity gated p and α spectra in low energy 12C+93Nb and 16O+89Y reactions
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ABSTRACT: Gamma ray multiplicity gated proton spectra have been measured in the reactions 12C+93Nb at E(12C)= 40 and 45.5 MeV and 16O+89Y at E(16O)= 51 and 54 MeV populating the CN 105 Ag at EX between 35 and 40 MeV. Broad structures are seen in all spectra at high gamma ray multiplicities. The present data, along with those from our earlier work on the former reaction at E(12C)= 42.5 MeV, establish the compound nuclear origin of the structures. The data can be explained by incorporating a localised enhancement of nuclear level density in the excitation energy and angular momentum space. Multiplicity gated Îś spectra have also been measured in the same reaction at E(12C)= 37.5 – 45 MeV. Broad structures seen in these spectra seem to have contribution from other reaction mechanisms also.EPJ Web of Conferences. 01/2010; -
Article: Exploring fusion at extreme sub-barrier energies with weakly bound nuclei.
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ABSTRACT: Results of measurement of residues formed in fusion of (6)Li with (198)Pt in the energy range of 0.68 < E/V(b) < 1.3 using a new sensitive off-beam technique are reported. The fusion excitation function and the derived average angular momenta do not indicate a change of slope at deep sub-barrier energies, contrary to recent observations. The present results for a system with weakly bound projectile confront the current understanding of the fusion hindrance at these low energies, underlying the role of internal reorganization on the dynamical path towards fusion.Physical Review Letters 12/2009; 103(23):232702. · 7.37 Impact Factor -
Article: Structures in angular momentum gated proton and alpha particle spectra in low-energy 12C and 16O induced reactions
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ABSTRACT: Gamma-ray multiplicity gated proton spectra have been measured in the 12C + 93Nb and 16O + 89Y reactions producing the same compound nucleus 105Ag at an excitation energy of ~39.8 MeV, and in the 12C + 89Y reaction at E(12C) = 40 MeV. Multiplicity gated alpha particle spectra have been measured in the 12C + 93Nb reaction at E(12C) = 37.5–45 MeV. All these measurements were aimed at gaining more insight into the origin of the unexpected broad structures seen earlier in the high energy part of the proton spectra at high gamma-ray multiplicities. Two possible explanations, one of the enhanced nuclear level density within the statistical model and the other of a massive cluster transfer process, were suggested by us to understand the earlier data. The former prescription appears to be favoured by the present proton data.Journal of Physics G Nuclear and Particle Physics 07/2009; 36(9):095103. · 4.18 Impact Factor -
Article: Absolute cross-sections from X–g coincidence measurements
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ABSTRACT: An activation technique using coincidences between characteristic X-rays and g-rays to obtain absolute cross-sections is described. This method is particularly useful in the case of nuclei that decay by electron capture. In addition to the reduction of possible contamination, an improved detection sensitivity is achieved as compared to inclusive measurements, thereby allowing the extraction of absolute fusion cross-sections in the nano-barn range. Results of this technique for 6Li + 198Pt system, at energies around the Coulomb barrier are described. Future applications with low intensity radioactive ion beams are also discussed.Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2008; 598:445. · 1.21 Impact Factor -
Article: A large area plastic scintillator detector array for fast neutron measurements
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ABSTRACT: A large area plastic scintillator detector array(~ 1 m x1m) has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for mono-energetic neutrons using the 7Li(p,n1)7Be*(0.429 MeV) reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7Li(p,n1) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4-12 MeV, in the reaction 12C+ 93Nb at E(12C)= 40 MeV. This is in reasonable agreement with a statistical model calculation.10/2008; -
Article: Broad structures in
http://dx.doi.org/10.1051/epjconf/20100204004. -
Article: Unusual feature of α spectra in the^{12} C+^{93} Nb reaction near Coulomb barrier energies
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ABSTRACT: Proton and α-particle spectra have been measured at backward angles in the 12C + 93Nb reaction at E(12C)=37.5–60 MeV and in the 16O+93Nb reaction at E(16O)=54–75 MeV. The inclusive particle spectra generally are in good agreement with the statistical model calculations except for the α spectra in the 12C-induced reaction at beam energies of 37.5–42.5 MeV which are close to the Coulomb barrier in the entrance channel. In these cases the evaporation peak is up to 2 MeV lower than its expected position from the statistical model predictions. Gamma-multiplicity-gated α spectra, measured in the same reaction, also show the aforementioned discrepancy. These observations reveal that the conventional statistical model cannot explain the α-particle spectra in the 12C-induced reactions near the Coulomb barrier.Phys. Rev. C. 82(6). -
Article: Exclusive giant dipole resonance measurement on the Jacobi transition in the^{19} F+^{27} Al system
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ABSTRACT: Evaporation-residue-gated high-energy gamma-ray spectra were measured in the 19F+27Al reaction at two beam energies of ∼75 and 125 MeV. The compound nuclear angular momenta populated at the higher energy should extend beyond the critical value for the Jacobi shape transition, while those at the lower energy should be mostly restricted below the critical value. A sharp low-energy (at ∼10 MeV) component has been observed in the gamma-ray strength function superimposed on a broad distribution. At the higher beam energy, the component becomes more prominent at higher angular momentum, whereas an opposite behavior is witnessed at the lower beam energy. The implication of these observations in connection with the occurrence of the Jacobi shape transition is discussed.Phys. Rev. C. 85(4). -
Article: Absolute cross-sections from X - $\gamma$ coincidence measurements
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Article: A large area plastic scintillator detector array for fast neutron measurements
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ABSTRACT: A large area plastic scintillator detector array () has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for monoenergetic neutrons using the 7Li reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7Li(p,n1) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4–12 MeV, in the reaction at . This is in reasonable agreement with a statistical model calculation.Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. -
Article: Structure in E1 strength distribution built on the 15.1 MeV T= 1 state in^{12} C
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ABSTRACT: The measurement of the giant electric dipole resonance built on the isobaric analog state in the self-conjugate even-even nucleus 12C is reported covering a wide excitation energy range. This is done using the 11B(p,γ) reaction leading to the 15.1 MeV T=1 state in 12C over a proton energy range of 7 to 24.5 MeV. Two resonances of 1.3 and 2 MeV widths are observed at excitation energies of 24.4 and 28.8 MeV superimposed on a smoothly varying cross section. The γ transitions from both the resonances are assigned E1 multipolarity. The structured T=0 component of the E1 strength distribution is thus very different from that built on the first T=1 state in the neighboring nucleus 14N and those built on the ground states of 12C and 14C.Phys. Rev. C. 77(5).
Top co-authors
Top Journals
Institutions
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2013
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Homi Bhabha National Institute
Mumbai, State of Maharashtra, India
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2009–2010
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Bhabha Atomic Research Centre
- Nuclear Physics Division
Mumbai, State of Maharashtra, India
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