Browsing by Author "N. Madhavan"

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A modular focal plane detector system for the heavy ion reaction analyzer at NSC, New Delhi
(Elsevier, 1996) D.O. Kataria; J.J. Das; N. Madhavan; P. Sugathan; A.K. Sinha; G. Dayanand; M.C. Radhakrishna; A.M. Vinodkumar; K.M. Varier; Mahendrajit Singh; N.V.S.V. Prasad
A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow preamplifiers, the position resolution is ≥1 mm and the time resolution is estimated to be 1.5 ns for the LP-MWPC. The ionization detector gives 2.4% energy resolution for 150 MeV 28Si scattered off a gold target and the ΔZ/Z obtained for 28Si+27Al is 1/42 for Z=14. Some results for fusion and transfer studies for the 48Ti+58Ni and 28Si+68Zn systems, respectively, at energies around the Coulomb barrier, are presented to highlight the performance of the detector system.
Bandcrossing of magnetic rotation bands in Pr137
(2007) Priyanka Agarwal; Suresh Kumar; Sukhjeet Singh; Rishi Kumar Sinha; Anukul Dhal; S. Muralithar; R.P. Singh; N. Madhavan; Rakesh Kumar; R.K. Bhowmik; S.S. Malik; S.C. Pancholi; L. Chaturvedi; H.C. Jain; A.K. Jain
The odd mass nucleus Pr137 has been studied to high spins in order to investigate the magnetic rotation phenomenon in mass 130 region using the Sn122(F19,4n)Pr137 reaction at a beam energy of 80 MeV. A known ΔI=1 band has been extended to Jπ=47/2- with the addition of three new transitions. Directional Correlation of Oriented Nuclei (DCO) ratios and linear polarization measurements have been performed to assign the multipolarities of gamma transitions and the spins and parities of the energy levels in this band, now established as the M1 band. The combination of M1 transitions along with cross over E2 transitions have been observed in this band for the first time. The experimentally deduced B(M1)/B(E2) ratios show a decrease with increasing spin after band-crossing suggesting magnetic rotation. TAC calculations for the 3qp: πh11/2 ν(h11/2)-2 configuration reproduce the experimental observations in the lower spin part of the ΔI=1 band and the 5qp: πh11/2(g7/2)2 ν(h11/2)-2 configuration reproduces the ΔI=1 band at higher spins; the crossing of the bands based on the two configuration leads to a back-bending also. Theoretical calculations also support a magnetic rotation nature for both the configurations. © 2007 The American Physical Society.
Candidates for twin chiral bands in Rh 102
(2014) D. Tonev; M.S. Yavahchova; N. Goutev; G. De Angelis; P. Petkov; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mohanto; A. Singh; N. Kaur; R. Garg; A. Shukla; Ts. K. Marinov; S. Brant
Excited states in Rh102, populated in the fusion-evaporation reaction Zr94(B11,3n)Rh102 at a beam energy of 36 MeV, were studied using the Indian National Gamma Array spectrometer at Inter University Accelerator Center, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in detail. A new chiral candidate sister band was found. Lifetimes of exited states in both chiral candidate bands of Rh102 were measured for the first time in the A∼100 mass region by means of the Doppler-shift attenuation technique. The derived reduced transition probabilities are compared to the predictions of the two quasiparticles plus triaxial rotor model. Both experimental results and calculations do not support the presence of static chirality in Rh102. © 2014 American Physical Society.
Check for chirality in 102Rh
(2012) D. Tonev; N. Goutev; M.S. Yavahchova; P. Petkov; G. De Angelis; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mahanto; A. Singh; N. Kaur; R. Garg; A. Sukla; Ts.K. Marinov; S. Brant
Excited states in 102Rh, populated by the fusion-evaporation reaction 94Zr(11B,3n)102Rh at a beam energy of 36 MeV, were studied using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in details. A new chiral candidate sister band was found in the level-scheme of 102Rh. Lifetimes of exited states in 102Rh were measured by means of the Doppler-shift attenuation technique. The experimental results do not support the presence of static chirality in 102Rh. © 2012 American Institute of Physics.
Does chirality exist in nuclei? The case of 102Rh
(Bulgarian Academy of Sciences, 2015) M.S. Yavahchova; D. Tonev; N. Goutev; G. De Angelis; P. Petkov; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mohanto; A. Singh; N. Kaur; R. Garg; A. Sukla; Ts.K. Marinov; S. Brant
Excited states in 102Rh, populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh at a beam energy of 36 MeV, were studied using the INGA spectrometer at IUAC, New Delhi. A new chiral candidate sister band was found. Lifetimes of exited states in 102Rh were measured for the first time by means of the Doppler-shift attenuation technique. A new band was found in the level-scheme of 102Rh. 1 band with a negative parity.
Dynamic chirality in mass regions A=105 and A=130
(Institute of Physics Publishing, 2018) M.S. Yavahchova; D. Tonev; G. De Angelis; P. Petkov; N. Goutev; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mohanto; A. Singh; N. Kaur; R. Garg; A. Shukla; R. Mateva; E. Geleva; B. Slavchev; S. Brant
Chiral symmetry is dichotomic and its spontaneous breaking by the axial angular momentum vector leads to a pair of degenerate ΔI = 1 rotational bands, called chiral doublet bands. In many cases the energy degeneracy of the chiral candidate bands has almost been observed but the transition probabilities of the analogue states have been found to be different. In the angular momentum region where chirality sets in the B(E2) values of the electromagnetic transitions deexciting analogue states of the chiral twin bands should be almost equal. Correspondingly the B(M1) values should exhibit staggering. Experimental data for two nuclei from different mass regions are compared with theoretical predictions. Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F, 4n)134Pr, while excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh. Our lifetime measurements and level-scheme investigations show that there are similarities in both chiral candidates nuclei related to dynamic chirality. © Published under licence by IOP Publishing Ltd.
Energetics and thermodynamic characteristics of the adsorption process responsible for the time variation of the joshi effect under, or/and in the absence of, continuous electrical excitation
(Springer-Verlag, 1962) M. Venugopalan; N. Madhavan
[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]
Evaporation residue cross-section measurements for 30Si+142Ce system
(Elsevier B.V., 2024) Amninderjeet Kaur; A. Kumar; Chetan Sharma; Neha Dhanda; Raghav; N. Madhavan; S. Nath; J. Gehlot; Gonika; Chandra Kumar; P. Sherpa; A. Parihari; Jyoti Pandey; A.K. Gupta; H.P. Sharma; B.R. Behera
Evaporation residue (ER) cross-sections were measured for 30Si+142Ce reaction at laboratory energies in the range of 105 - 132 MeV using the HYbrid Recoil mass Analyzer (HYRA) at IUAC, New Delhi. The transmission efficiency of the HYRA was estimated using the calibration reaction 28Si+142Ce. Sub-barrier fusion enhancement was observed when compared with the one-dimensional barrier penetration model predictions for the present system. To explore the phenomena responsible for sub-barrier fusion enhancement, coupled-channels calculations were performed using the CCFULL code. The effect of couplings and the role of positive Q-value neutron transfer (PQNT) channels on sub-barrier fusion cross-sections were investigated. Coupled-channels calculations were able to reproduce the data by including the coupling in both projectile and target nucleus along with two neutron-transfer channels having positive Q-value. The measured ER cross-sections were compared with the nearby systems to explore the role of deformation of the colliding nuclei. © 2023 Elsevier B.V.
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.
Examples of dynamic chirality in nuclei
(EDP Sciences, 2018) M.S. Yavahchova; D. Tonev; N. Goutev; G. De Angelis; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mahanto; A. Singh; N. Kaur; R. Garg; A. Sukla
In many cases the chirality was almost observed but the transition probabilities are different. This fact is clearly seen in the cases of 134Pr and 102Rh. In the case of chirality, the yrast and the side bands should be nearly degenerate. In the angular momentum region where chirality sets, the B(E2) values of the electromagnetic transitions deexciting analog states of the chiral twin bands should be almost equal. Correspondingly the B(M1) values should exhibit staggering. Our lifetime measurements in the cases of 134Pr and 102Rh and the theoretical analysis do not support static chirality. Chirality has mainly a dynamical character in both nuclei. In the present paper, we compare our results with the results for other chiral candidate nuclei, which fulfill static chirality conditions. © The Authors, published by EDP Sciences, 2018.
High spin states in 70Ge
(2000) B. Mukherjee; S. Muralithar; G. Mukherjee; R.P. Singh; R. Kumar; J.J. Das; P. Sugathan; N. Madhavan; P.V. Madhusudanan Rao; A.K. Sinha; A.K. Pande; L. Chaturvedi; S.C. Pancholi; R.K. Bhowmik
High spin states in 70Ge nucleus have been studied in two different experiments using heavy ion fusion evaporation reaction. The Gamma Detector Array, comprising of eight Compton-suppressed High Purity Ge detectors, was used in conjunction with a recoil mass spectrometer - the HIRA - in order to identify and measure the transitions of this weakly populated nucleus. The level scheme is extended up to an excitation energy of 13 MeV for spin-parity 21- with several newly observed transitions placed in it. A rotational like band is also observed in this nucleus for the first time.
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.
In a search for a chiral symmetry in 102Rh
(Institute of Physics Publishing, 2014) M.S. Yavahchova; D. Tonev; N. Goutev; P. Petkov; G. De Angelis; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mohanto; A. Singh; N. Kaur; R. Garg; A. Sukla; Ts K. Marinov; S. Brant
Excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(nB, 3n)102Rh at a beam energy of 36 MeV, using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the γ-ray transitions observed in 102Rh were investigated in detail. A new candidate for a chiral twin band was identified in 102Rh for the first time.
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.
Investigation of chirality in the case of 102Rh
(Institute of Physics Publishing, 2016) M.S. Yavahchova; D. Tonev; N. Goutev; G. De Angelis; P. Petkov; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mahanto; A. Singh; N. Kaur; R. Garg; A. Sukla; Ts. K. Marinov; R.R. Mateeva; S. Brant
Excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh at a beam energy of 36 MeV using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in details. A new chiral candidate sister band was found. Lifetimes of exited states in 102Rh were measured using the Doppler-shift attenuation technique and the derived reduced transition probabilities are compared to the predictions of the Two Quasiparticles Plus Triaxial Rotor model. © Published under licence by IOP Publishing Ltd.
Level scheme investigation of 102Rh
(Institute of Physics Publishing, 2012) N. Goutev; M.S. Yavahchova; D. Tonev; G. De Angelis; P. Petkov; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mahanto; A. Singh; N. Kaur; R. Garg; A. Sukla; Ts.K. Marinov; S. Brant
Excited states in102Rh were populated in the fusion-evaporation reaction 96Zr(11B, 3n)102 Rh. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in detail. A new chiral candidate sister band was found in the level-scheme of 102Rh.
Lifetime measurements in mass regions A=100 and A=130 as a test for chirality in nuclear systems
(EDP Sciences, 2016) D. Tonev; M.S. Yavahchova; G. De Angelis; S. Brant; S. Frauendorf; P. Petkov; A. Dewald; Q. Zhong; D. Curien; N. Goutev; R.K. Bhowmik; R.P. Singh; S. Muralithar; N. Madhavan; R. Kumar; M. Kumar Raju; J. Kaur; G. Mahanto; A. Singh; N. Kaur; R. Garg; A. Sukla; E. Geleva; Ts. K. Marinov
Two odd-odd nuclei from the A ∼ 100 and A ∼ 130 regions, namely 102Rh and 134Pr have been studied in search for chiral doublet bands via 94Zr(11B,3n)102Rh and 119Sn(19F,4n)134Pr reactions, respectively. Two nearly degenerate bands built on the πg9/2 ⊗ νh11/2 configuration have been identified in 102Rh and on the πg11/2 ⊗ νh11/2 configuration for 134Pr. Lifetimes of excited nuclear states were measured using Dopplershift attenuation method and recoil distance Doppler-shift method. The deexciting gamma rays were registered by the Indian National Gamma Array for 102Rh and using the EUROBALL IV detector array with an inner Bismuth Germanate (BGO) ball for 134Pr, respectively. Polarization and angular correlation measurements have been performed to establish the spin and parity assignments for these bands. The derived reduced transition probabilities are compared to the predicitons of the two quasiparticles + triaxial rotor and interacting boson fermion-fermion models. © 2016 Owned by the authors, published by EDP Sciences.
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.