Browsing by Author "R.K. Sinha"

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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]
Evidence of antimagnetic rotation in odd-A Cd105
(American Physical Society, 2010) Deepika Choudhury; A.K. Jain; M. Patial; N. Gupta; P. Arumugam; A. Dhal; R.K. Sinha; L. Chaturvedi; P.K. Joshi; T. Trivedi; R. Palit; S. Kumar; R. Garg; S. Mandal; D. Negi; G. Mohanto; S. Muralithar; R.P. Singh; N. Madhavan; R.K. Bhowmik; S.C. Pancholi
The lifetimes of the levels above spin 23/2⊃- in the negative-parity yrast band of Cd105 have been measured using the Doppler shift attenuation method. The obtained B(E2) values are small and show a decrease with an increase in spin. This establishes, for the first time, antimagnetic rotation (AMR) in an odd-A nucleus. An excellent agreement between the theoretical (semiclassical model) and experimental results along with a large I(2)/B(E2) ratio for the states strongly suggests that the structure of the levels beyond spin 23/2⊃- has the character of a twin-shears type AMR band resulting from the coupling of a pair of g9/2 proton holes with aligned h11/2 and (g7/2)2 neutron particles, along with a small contribution from the core rotation. © 2010 The American Physical Society.
Formation behaviour of YBa2Cu3O7-x- conventional processing
(1993) R.K. Sinha; S.K. Srivastava
The sequence of formation of intermediate phases during the processing of YBa2Cu3O7-x from oxide and carbonate raw materials by a conventional solid-state route is studied in detail using a combination of simultaneous thermal analysis (DTA and TG) and X-ray diffraction analysis. The rapid formation of Y2Cu2O5, its conversion to Y2BaCuO5 and the final formation of YBa 2Cu3O7-x from the reaction between the intermediate phase and remaining raw materials are observed as a function of time. The study is expected to help in the design of an intermediate phase free process for forming YBa2Cu3O7-x.
High spin spectroscopy and shears mechanism in In107
(American Physical Society, 2010) D. Negi; T. Trivedi; A. Dhal; S. Kumar; V. Kumar; S. Roy; M.K. Raju; S. Appannababu; G. Mohanto; J. Kaur; R.K. Sinha; R. Kumar; R.P. Singh; S. Muralithar; A.K. Bhati; S.C. Pancholi; R.K. Bhowmik
High spin states of In107 have been investigated using the reaction Mo94(O16,p2n)In107 at a beam energy of 70 MeV. A total of 62 new γ transitions have been placed in the level scheme and several ΔI=1 sequences and one ΔI=2 sequence have been found. Lifetime measurements using the Doppler-shift attenuation method (DSAM) have been carried out for band states of ΔI=1 and ΔI=2. A decreasing trend of B(M1) strengths with increasing spin deduced for the ΔI=1 band indicates the presence of a shears mechanism. The experimental data for this band are compared with the tilted axis cranking (TAC) calculations. The ΔI=2 band has been found to be a deformed band with β2~0.2. © 2010 The American Physical Society.
High spin states in Pm139
(American Physical Society, 2009) A. Dhal; R.K. Sinha; L. Chaturvedi; P. Agarwal; S. Kumar; A.K. Jain; R. Kumar; I.M. Govil; S. Mukhopadhyay; A. Chakraborty; Krishichayan; S. Ray; S.S. Ghugre; A.K. Sinha; R. Kumar; R.P. Singh; S. Muralithar; R.K. Bhowmik; S.C. Pancholi; J.B. Gupta
The odd mass nucleus Pm139 has been studied to high spins through the Cd116(Al27,4n)Pm139 reaction at an incident beam energy of 120 MeV. The de-exciting γ-rays were detected using an array of 12 Compton suppressed Ge detectors. A total of 46 new levels have been proposed in the present work as a result of the observation of 60 new γ-rays. Four new bands including a ΔJ=1 sequence have been identified and all the earlier reported bands, other than the yrast band, have been extended to higher spins and excitation energy. The spin assignments for most of the newly reported levels have been made using the observed coincidence angular anisotropy. Tilted axis cranking calculations support the interpretation of two of the observed magnetic dipole sequences as examples of magnetic rotational bands. © 2009 The American Physical Society.
High-spin states in the odd-odd nucleus146Tb
(American Physical Society, 2004) Krishichayan; A. Chakraborty; S.S. Ghugre; R. Goswami; S. Mukhopadhyay; N.S. Pattabiraman; S. Ray; A.K. Sinha; S. Sarkar; P.V. Madhusudhana Rao; U. Garg; S.K. Basu; B.K. Yogi; L. Chaturvedi; A. Dhal; R.K. Sinha; M. Saha Sarkar; S. Saha; R. Singh; R.K. Bhowmik; A. Jhingan; N. Madhavan; S. Muralithar; S. Nath; R.P. Singh; P. Sugathan
The odd-odd 146Tb nucleus has been investigated using the 115In(34S,3n) reaction at 140 MeV incident energy using an array of eight Compton-suppressed Clover detectors. Based on the observed γ- γ coincidences, the level structure of 146Tb has been extended up to Ex∼ 10 MeV. Linear polarization measurements have been combined with angular correlations of the observed γ rays to assign the electromagnetic nature to the transitions. Probable origin of a cascade of M1 transitions observed around 8 MeV excitation energy has been discussed.
Influence of wollastonite on processing and dielectricbehaviour of barium titanate
(1989) R.K. Yadavalli; R.K. Sinha
Samples of barium titanate with wollastonite additions of up to 5 weight per cent were fabricated by conventional technique and studied. The room temperature dielectric constant increased up to 1 per cent wollastonite and then decreased. The curie temperature increases with increasing wollastonite content while the peak value of dielectric constant decreases and the peak itself is broadened. The crystal structure shifts from tetragonal towards cubic symmetry with shortening of lattice parameters and the microstructure shows a residual grain boundary phase.
Lifetime measurements of microsecond isomers in the N=48 nuclei 88Zr and90Mo using recoil-isomer tagging
(American Physical Society, 2004) A. Chakraborty; Krishichayan; S.S. Ghugre; R. Goswami; S. Mukhopadhyay; N.S. Pattabiraman; S. Ray; A.K. Sinha; S. Sarkar; P.V. Madhusudhana Rao; U. Garg; S.K. Basu; L. Chaturvedi; A. Dhal; R.K. Sinha; I.M. Govil; M.B. Chatterjee; M. Saha Sarkar; R.K. Bhowmik; A. Jhingan; N. Madhavan; S. Muralithar; S. Nath; R.P. Singh; P. Sugathan
The recoil-isomer tagging technique has been used to study the isomeric states of nuclei in the vicinity of the N=50 shell closure. The nuclei of interest were separated from the projectilelike nuclei and other evaporation residues and transported to the focal plane of a recoil separator. The decay of the tagged isomer was studied at the focal plane using a high-purity Ge detector. The prompt transitions feeding the isomer were detected in an array of Clover Ge detectors placed around the target. The measured half-lives of the 8+ isomers in 88Zr and 90Mo are 1.41 (-0.09)(+0.12) μs and 1.17(-0.07) (+0.19), respectively. The corresponding transition probabilities are in reasonable agreement with the predictions of shell model calculations. The systematics of effective charges (ep and en) for N=48 nuclei are qualitatively understood in these calculations.
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.
Optimisation of annealing condition for the prepration of (Bi 5Pb)-Sr-Ca-Cu-O HTSC films by spray pyrolysis technique
(2010) K.K. Verma; R.K. Sinha; R.S. Tiwari; O.N. Srivastava
High temperature superconducting (HTSC) films (Bi1Pb)-Sr-Ca-Cu-O have been prepared by spray pyrolysis technique on MgO (100) single crystal substrate. Annealing steps in regard to oriented nature of the films have been studied in detail which have been confirmed by XRD and SEM results. The optimized film has shown maximum Tc (R=0) of ∼82 K and /c is ∼6×l03 cm-2 at 77 K.
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.
Shape coexistence and high spin states in Cr52
(2007) Rajesh Kumar; S.K. Chamoli; I.M. Govil; A. Dhal; R.K. Sinha; L. Chaturvedi; Z. Naik; C.R. Praharaj; S. Muralithar; R.P. Singh; N. Madhavan; P. Sugathan; J.J. Das; R.K. Bhowmik
High spin states in Cr52 have been populated by means of the reaction Al27(Si28,3p)Cr52 at a beam energy of 70 MeV and studied with an array, consisting of eight Compton-suppressed clover germanium detectors. Eleven new γ rays have been assigned to Cr52 and placed in the level scheme. The level structure of Cr52 has been extended up to Ex 10 MeV. Spins and parities have been assigned to many of the levels on the basis of directional correlations and linear polarization measurements. The band structures are discussed in the framework of cranked Woods-Saxon and deformed Hartree-Fock (HF) models. Both the oblate and prolate orbits are considered for J projection in the HF model. The K=0+ band is properly understood if we consider the J projection from both prolate and oblate orbits and collectivity shown by the K=4+ band to be accounted for by taking the J projection from prolate HF configurations. Thus there is prolate and oblate shape coexistence in Cr52. © 2007 The American Physical Society.
Shape evolution in odd-A 137 Pm
(Springer New York LLC, 2012) A. Dhal; R.K. Sinha; D. Negi; T. Trivedi; M.K. Raju; D. Choudhury; G. Mohanto; S. Kumar; J. Gehlot; R. Kumar; S. Nath; S.S. Ghugre; R.P. Singh; J.J. Das; S. Muralithar; N. Madhavan; J.B. Gupta; A.K. Sinha; A.K. Jain; I.M. Govil; R.K. Bhowmik; S.C. Pancholi; L. Chaturvedi
The odd mass nucleus 137Pm has been studied to high spins through the 109Ag(32S, 2p2n)137Pm reaction at an incident beam energy of 150 MeV. The de-exciting γ-rays were detected using an array of 18 Compton suppressed clover detectors. The level scheme of 137Pm has been extended up to Jπ = 43/2- and excitation energy of Ex ≅ 6 MeV with the observation of 42 new gamma transitions. The linear polarization (IPDCO) measurements for the γ-ray transitions have been done for the first time. The spin and parity assignments for most of the reported levels have been made using these results and the coincidence angular anisotropy (RDCO) measurements. The nuclear shape evolution is discussed in the light of Total Routhian Surface (TRS) and Cranked Shell Model (CSM) calculations. © 2012 SIF, Springer-Verlag Berlin Heidelberg.
Shears mechanism in 109In
(American Physical Society, 2012) D. Negi; T. Trivedi; A. Dhal; S. Kumar; V. Kumar; S. Roy; M.K. Raju; S. Appannababu; G. Mohanto; J. Kaur; R.K. Sinha; D. Choudhury; D. Singh; R. Kumar; R.P. Singh; S. Muralithar; A.K. Bhati; S.C. Pancholi; R.K. Bhowmik
High spin states of 109In were investigated using the reaction 96Zr(19F, 6n)109In at a beam energy of 105 MeV. New level sequences have been found in this nucleus. In an earlier known band, the ordering of some of the transitions have been changed and assigned a three-quasiparticle π(g9/2) -1 âŠ - ν[h11/2(d5/2/g7 /2)] configuration. Similar three-quasiparticle bands have also been found earlier in lighter mass 105In and 107In nuclei. Systematics of these bands in 105In, 107In, and 109In nuclei are discussed in the present work within the framework of the tilted axis cranking model. © 2012 American Physical Society.
SINTERING AND DIELECTRIC BEHAVIOUR OF TITANIA - RAJMAHAL CLAY MIXTURES.
(India, 1985) B. Singh; R.K. Sinha; S.P. Singh
Rajmahal clay, calcined at 800 degree C for eight hours and dry ball milled for 24 hours is used for preparing TiO//2 clay mixtures with 20, 40, 60, and 80 per cent clay respectively. Pellets are prepared from pure TiO//2 pure clay and the above mixtures by unidirectional pressing in a die (2. 5 cm diameter). Pellets are fired at 1200, 1250, 1300 and 1350 degree C respectively for up to two hours. Variation of density with time and temperature is studied. Attempt is made to correlate sintering parameters with the microstructure on the one hand and the microstructure and the dielectric behaviour on the other.
Spectroscopy of Nb90 at high spin
(2005) A. Chakraborty; Krishichayan; S.S. Ghugre; R. Goswami; S. Mukhopadhyay; N.S. Pattabiraman; S. Ray; A.K. Sinha; S. Sarkar; P. V. Madhusudhana Rao; U. Garg; S.K. Basu; M.B. Chaterjee; M. Saha Sarkar; L. Chaturvedi; A. Dhal; R.K. Sinha; I.M. Govil; R.K. Bhowmik; A. Jhingan; N. Madhavan; S. Muralithar; S. Nath; R.P. Singh; P. Sugathan
Excited states of Nb90 were investigated via prompt and delayed γ decays and the recoil-isomer tagging technique. The level scheme of Nb90 has been extended up to J=19 and Ex=8.4 MeV. Half-lives of the 11- and 17/2- isomeric levels in Nb90,91 were measured to be 0.47±0.01 and 3.3±0.4 μs, respectively. The results are compared with the predictions of large-basis shell model calculations. The effects of truncation of the valence model space on the calculated results are discussed. © 2005 The American Physical Society.
Spin-parity measurements in the neutron-rich N ∼ 20 34P and 36S nuclei
(2006) Krishichayan; A. Chakraborty; S. Mukhopadhyay; S. Ray; N.S. Pattabiraman; S.S. Ghugre; R. Goswami; A.K. Sinha; S. Sarkar; U. Garg; P.V. Madhusudhana Rao; S.K. Basu; B.K. Yogi; L. Chaturvedi; A. Dhal; R.K. Sinha; M. Saha Sarkar; S. Saha; R. Singh; R.K. Bhowmik; A. Jhingan; N. Madhavan; S. Muralithar; S. Nath; R.P. Singh; P. Sugathan
Yrast and near-yrast energy levels in the neutron-rich N ∼ 20 nuclei 34P, 36S were populated using transfer/deep-inelastic processes following the 34S + 115In reaction at an incident energy of 140MeV. The use of a multi-clover array has facilitated polarization measurements of the observed γ-rays and necessitated some changes in the previously known level scheme. The observation of the negative-parity levels in these nuclei on the periphery of the "island of inversion" is indicative of the influence of the intruder orbitals on the level structure at low spins. Shell-model calculations indicate that the inclusion of the orbitals from the upper pf shell is important even for the low-lying positive-parity states.
The influence of atmosphere on the formation behaviour of YBa 2Cu3O7-x
(1994) R.K. Sinha; S.K. Srivasatava
The influence of reduced local partial pressure of CO2 due to virtually open atmosphere conditions on the sequence of reactions during the synthesis of YBa2Cu3O7-x from Y 2O3, BaCO3 and CuO in air has been studied. Under these conditions, formation of (123) is observed to be complete within the first 30 min of calcination, through a reaction between intermediate phases Y2Cu2O5 and BaCuO2. Y 2Cu2O5 also reacts with BaCO3, BaCuO2, and probably YBa2Cu3O7-x, individually to form Y2BaCuO5. The rapidly formed superconducting phase (123) is, however, unstable and decomposes into (211), BaO and CuO. BaO, thus released reacts with CO2 to form BaCO 3. (211) reacts with other raw materials forming a stable (123) with (211) as the major impurity phase.