Publications (23)8.78 Total impact
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Article: Fusion cross sections for 6,7Li + 24Mg reactions at energies below and above the barrier
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ABSTRACT: Measurement of fusion cross sections for the 6,7Li + 24Mg reactions by the characteristic gamma-ray method has been done at energies from below to well above the respective Coulomb barriers. The fusion cross sections obtained from these gamma-ray cross sections for the two systems are found to agree well with the total reaction cross sections at low energies. The decrease of fusion cross sections with increase of energy is consistent with the fact that other channels, in particular breakup open up with increase of bombarding energy. This shows that there is neither inhibition nor enhancement of fusion cross sections for these systems at above or below the barrier. The critical angular momenta (lcr) deduced from the fusion cross sections are found to have an energy dependence similar to other Li - induced reactions.06/2008; -
Article: Indication of the onset of collectivity in^{30} P
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ABSTRACT: 30P has been studied by in-beam γ-spectroscopy following the fusion-evaporation reaction 16O(16O,pn) at Elab=40 MeV, using the Indian National Gamma (Clover) Array (INGA) up to moderate spins (I=5). Polarization measurements of seven gamma rays have been performed for the first time. To understand the underlying structure of the levels and transition mechanisms, experimental data have been compared with the results from large basis cross-shell shell model calculations. The results for the negative parity states are especially important in this respect. Positive parity states indicate an onset of collectivity, whereas the negative parity states are members of ν-π multiplets.Phys. Rev. C. 09/2007; 76(3). -
Article: High spin states in^{143} Sm
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ABSTRACT: The high spin states of 143Sm have been studied by in-beam γ-spectroscopy following the reaction 130Te(20Ne,7n)143Sm at Elab=137 MeV, using a Clover detector array. More than 50 new gamma transitions have been placed above the previously known Jπ=23/2-, 30 ms isomer at 2795 keV. The level scheme of 143Sm has been extended up to 12 MeV and spin-parity assignments have been made to most of the newly proposed level. Theoretical calculation with the relativistic mean field approach using blocked BCS method, has been performed. A sequence of levels connected by M1 transitions have been observed at an excitation energy ∼8.6 MeV. The sequence appears to be a magnetic rotational band from systematics.Phys. Rev. C. 04/2006; 73(4). -
Article: Influence of projectile - breakup threshold on complete fusion
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ABSTRACT: Complete fusion excitations for 11,10B+159Tb have been measured at energies around the respective Coulomb barriers, and the existing complete fusion measurements for 7Li+159Tb have been extended to higher energies. The measurements show significant reduction of complete fusion cross sections at above-barrier energies for both the reactions, 10B+159Tb and 7Li+159Tb, when compared to those for 11B+159Tb. The comparison shows that the extent of suppression of complete fusion cross sections is correlated with the -separation energies of the projectiles. Also, the two reactions, 10B+159Tb and 7Li+159Tb were found to produce incomplete fusion products at energies near the respective Coulomb barriers, with the - particle emitting channel being the favoured incomplete fusion process in both the cases. Comment: 10 pages, 4 figures To be published in Phys. Letts. B03/2006; -
Article: Absence of M2 Retardation in $^{35}Cl$: Evidence for Stronger Isospin-Mixing Effects in A=35 Mirror Nuclei
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ABSTRACT: The lifetime of the 3163 keV, 7/2$^-$ isomeric state in $^{35}Cl$ that decays by a stretched M2 transition to the $3/2^+$ ground state, has been re-measured using the Doppler Shift Attenuation Method, by gating on the 1185 keV transition which directly feeds this state. This eliminates the uncertainties in the measurement arising from the direct feedings from the continuum. A mean life of 0.6$^{+0.5}_{-0.2}$ ps has been obtained from the present work. This is considerably smaller than the adopted value 45.3(6) ps. Implication of this major reduction in the lifetime has been pointed out.08/2005; -
Article: Observation of magnetic rotation in odd-odd^{104} Ag
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ABSTRACT: The high spin level structure of 104Ag has been extended to Iπ=20+ and excitation energy of 7.159 MeV through the discrete line γ-ray spectroscopy. The negative parity ground state band has been confirmed and extended to Iπ=18−. Two new nonyrast dipole bands, one with positive and the other with negative parity, have been observed. The parities of the two bands have been established through polarization directional correlation measurement of the feed-out transitions from these bands. The level lifetimes have been measured in the ground state band and the positive parity dipole band. The measured total angular momenta and the B(M1) rates have been compared with the predictions of hybrid version of the tilted axis cranking. The B(M1) rates have also been compared with the values obtained from Dönau’s geometric formula. The tilted axis calculations give good overall agreement which suggests that all the three bands of 104Ag exhibits magnetic rotation.Phys. Rev. C. 04/2004; 69(4). -
Article: Fusion cross sections for^{7} Li+^{16} O at energies above barrier
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ABSTRACT: Measurement of fusion cross sections for the 7Li+16O reaction by the γ-ray method has been done in the energy interval Ec.m.=12.5–23.6 MeV (where c.m. means center-of-mass). The γ-ray data obtained at high bombarding energies are found to be in agreement with those obtained by the evaporation residue method. The present data, together with the previous γ-ray data, show that there is no fusion suppression at energies below and near the Coulomb barrier.Phys. Rev. C. 11/2003; 68(6). -
Article: Possible coexistence of principal and tilted axis rotation in^{103} Ag
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ABSTRACT: The high spin states of 103Ag have been populated through the 76Ge(35Cl,α4nγ)103Ag reaction using 132-MeV 35Cl beam. The presence of a positive parity ground state band and two negative parity bands decaying predominantly by M1 transitions in 103Ag has been confirmed. In addition, seven new crossover E2 transitions have been observed in the negative parity bands. The experimental B(M1)/B(E2) ratios are compared with the values obtained from the Dönau geometric formula for the negative parity bands based on single particle configurations assigned from signature arguments. These ratios are also compared to those obtained from the hybrid version of tilted axis cranking. A systematic study of odd-Ag isotopes seems to indicate that the signature symmetry is retained in 103Ag due to the shallow tilted minimum.Phys. Rev. C. 01/2003; 67(1). -
Article: Level structure of odd-odd 68Ga
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ABSTRACT: Excited states of 68Ga have been investigated through the 55Mn(16O, 2pn) reaction at projectile energy 55 MeV. The level scheme has been extended up to 7.8 MeV. Altogether six new excited levels could be identified and twelve previously unobserved γ-transitions have been placed in the modified level scheme.European Physical Journal A 10/2000; 9(2):197-200. · 2.19 Impact Factor -
Article: Shape of the nucleus
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ABSTRACT: The level structure of has been studied through () reactions using an in-beam -ray spectroscopic technique. The results of the present investigation are in agreement with the available experimental data on the level scheme and multipolarities of several -transitions. No new level has been found to be excited in the present work. A symmetric rotor - particle model calculation of the level properties of this isotope has been carried out. A comparison of the results of the present work with those obtained earlier shows that there is no definite experimental and theoretical evidence for the presence of triaxiality in the equilibrium shape of this nucleus.Journal of Physics G Nuclear and Particle Physics 12/1998; 23(2):169. · 4.18 Impact Factor -
Article: Rotational band in111Sn
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ABSTRACT: Partial level scheme of the neutron deficient111Sn isotope is established upto an excitation energy of about 9 MeV and I=43/2– from -rays following103Rh(12C, p3n) reaction. Clear evidence for the existence of a negative parity rotational band above=23/2–, most probably based on 3p-2h configuration, is obtained.Zeitschrift für Physik A Hadrons and Nuclei 02/1995; 351(1):1-2. -
Article: Oblate bands in doubly odd 134La
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ABSTRACT: The band structures of the doubly odd 134La nucleus have been investigated using the 133Cs(α, 3n) 134La reaction at a beam energy of 40 MeV. Altogether six bands have been established, of which details of the yrast band were only known from earlier works. A negative parity oblate band has also been observed in this nucleus. The observed level properties of the members of the yrast band have been compared with theoretical calculations performed within the Particle Rotor Model (PRM) with axially symmetric core. The experimental branching ratios, values and mixing ratios of the transitions in the yrast band are well reproduced by PRM, assuming an axial oblate core. A cranked shell model calculation has been carried out for the proposed bands.Nuclear Physics A. -
Article: Study of yrast band in 155Tm
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ABSTRACT: The nucleus 155Tm has been studied by a detailed in-beam gamma spectroscopy following the reaction 144Sm(14N, 3n)155Tm, at a beam energy, , using a Compton suppressed gamma detector array. More than 25 new gamma transitions have been placed in the proposed scheme and the latter has been extended upto a spin-parity of (51/2−) at an excitation energy ∼ 6 MeV.Nuclear Physics A. -
Article: High spin structure of 35Cl and the sd–fp shell gap
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ABSTRACT: The high spin states of 35Cl have been studied by in-beam γ-spectroscopy following the fusion–evaporation reaction 12C(28Si,αp)35Cl at Elab=70 and 88 MeV, using the Indian National Gamma (Clover) Array (INGA). Lifetimes of six new excited states have been estimated for the first time. To understand the underlying structure of the levels and transition mechanisms, experimental results have been compared with those from the large basis cross-shell shell model calculations. Involvement of orbitals from fp shell and squeezing of the sd–fp shell gap seem to be essential for reliable reproduction of high spin states.Nuclear Physics A. -
Article: 7Li+12C and 7Li+13C fusion reactions at subbarrier energies
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ABSTRACT: The 7Li+12C and 7Li+13C reactions have been studied at incident energies below and around the Coulomb barrier, by the measurement of cross sections for the characteristic γ-rays emitted from the residual nuclei. Statistical model calculations of the decay of the compound nucleus have been used to deduce the absolute cross sections for different channels and to obtain the total fusion cross sections. There is no evidence for fusion cross section limitations for these systems at energies near the Coulomb barrier as observed in an earlier experiment.Nuclear Physics A. 596(2):299-328. -
Article: Characterisation of a Compton suppressed Clover detector for high energy gamma rays
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ABSTRACT: Gamma ray spectra of two (p,γ) resonances have been utilised for the characterisation of the Clover detector at energies beyond 5 MeV. Apart from the efficiency and the resolution of the detector, the shapes of the full energy peaks as well as the nature of the escape peaks which are also very crucial at higher energies have been analysed with special attention. Proper gain matching in software have checked deterioration in the energy resolution and distortion in the peak shape due to addback. The addback factors show sharp increasing trend even at energies around 11 MeV.Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 556(1):266-272. · 1.21 Impact Factor -
Article: Characteristics of a Compton suppressed Clover detector up to 5MeV
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ABSTRACT: The Clover detectors in their addback mode are excellent tools for detecting high-energy gamma rays . The characteristics of these detectors, at energies above , are usually determined from simulation data or from extrapolation of the empirical data. This is the first time that the characteristics of a Compton suppressed Clover germanium detector have been studied up to using a radioactive source.Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 491:113-121. · 1.21 Impact Factor -
Article: Fusion cross sections for 7Li + 11B and 9Be + 9Be reactions at low energies
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ABSTRACT: The partial cross sections for the and reactions below and above the Coulomb barrier energy have been determined from the cross sections of the characteristic γ-rays of the residual nuclei and using the branching factor obtained from the statistical model calculations. The fusion cross sections obtained from the sum of these partial cross sections are found to be equal to the total reaction cross sections upto an energy well above the Coulomb barrier energy for the reaction. For the reaction, however, the fusion cross sections are found to be less than the total reaction cross sections at energies not much above the Coulomb barrier.The maximum fusion cross sections for the and reactions are found to be ∼66% and ∼81% of the total reaction cross sections at Ec.m. = 2Bc (where Bc is the Coulomb barrier energy), respectively.Nuclear Physics A. 614(2):238-260. -
Article: Fusion cross sections for 6Li+12C and 6Li+13C reactions at low energies
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ABSTRACT: The partial cross sections for the 6Li+12C and 6Li+13C reactions below and above the Coulomb barrier energy have been determined from the cross sections of the characteristic γ-rays measured with HPGe detectors and using the branching factor obtained from the statistical model calculations. The fusion cross sections obtained from the sum of these partial cross sections are found to be equal to the total reaction cross sections upto an energy well above the Coulomb barrier energy and there appears to be no evidence for limitation of fusion cross sections for these systems at such energies contrary to the evaporation residue measurements. The measured cross sections are also found to agree nicely with the IWBC (Incoming Wave Boundary Condition) and one-dimensional BPM (Barrier Penetration Model) calculation.Nuclear Physics A. 635(3):305-324. -
Article: Band structure in^{95} Ru
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ABSTRACT: The 95Ru nucleus has been studied through the 94Mo(α,3n)95Ru reaction. A level scheme has been proposed from γ-γ coincidence data and spin assignments are made on the basis of the results of angular distribution measurements. A rotation-particle coupling calculation has been performed and the proposed level scheme is discussed in the light of its predictions. The results obtained in the present work are also compared to those of previous investigations on this nucleus.Phys. Rev. C. 42(4).
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Institutions
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1995–2007
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Saha Institute of Nuclear Physics
Calcutta, Bengal, India
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