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Shape of80Krat high spin

Physical Review C, 2001

Lifetimes of eight high spin states were measured in the yrast band of even-even nucleus 80 Kr by... more Lifetimes of eight high spin states were measured in the yrast band of even-even nucleus 80 Kr by Doppler shift attenuation method. High spin states were populated by the heavy ion fusion evaporation reaction 65 Cu(19 F,2p2n) 80 Kr. The transition quadrupole moments, extracted from the lifetimes of the states, show a decreasing tendency after the band crossing indicating a change in shape of 80 Kr at high spin. The total Routhian surface calculations, using Woods-Saxon mean field potential and BCS pairing with Strutinsky shell correction procedure, predict a change from a near oblate to near prolate shape with small deformation along the yrast band at high spin in 80 Kr. The present experimental Q t values and the second alignment in the yrast band of 80 Kr support the predicted change in shape.

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Observation of antimagnetic rotation inCd108

Physical Review C, 2005

High spin levels in 108 Cd have been populated through 100 Mo(13 C,5nγ) 108 Cd reaction using a 6... more High spin levels in 108 Cd have been populated through 100 Mo(13 C,5nγ) 108 Cd reaction using a 65 MeV 13 C beam. The lifetime of the 14 + , 16 + , 18 + , and 20 + levels of the positive parity yrast band of 108 Cd have been measured using the Doppler shift attenuation method. The evaluated B(E2) values from the measured lifetimes have been compared with the B(E2) values calculated using the semiclassical model, which assume shears mechanism, and the values obtained from total Routhian surface (TRS) calculations. Both calculations show good agreement with the measured values. In addition, the large J (2) /B(E2) ratio may indicate that a large contribution to the angular momentum of this band is generated by shears mechanism. Thus, the present work indicates that the states of the positive parity yrast band from 16 + onwards in 108 Cd, originate due to antimagnetic rotation.

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Experimental investigation of fusion ofLi7+Si28above the Coulomb barrier

Physical Review C, 2007

Excitation functions for the above-barrier fusion cross sections are measured for the first time ... more Excitation functions for the above-barrier fusion cross sections are measured for the first time for the 7 Li+ 28 Si system by two methods-the characteristic γ-ray method and the evaporation α measurement method-in the energy range E lab = 11.5-26 MeV. Experimental results are consistent and agree with each other, and the one-dimensional Barrier Penetration Model (BPM) predictions describe the data well up to twice the Coulomb barrier, but they overestimate the data by about 15-20% at higher energies.

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Lifetimes of nuclear excited states with neutron gated recoil distance method

Pramana, 1999

A motor driven plunger has been constructed for measuring lifetimes of nuclear excited states in ... more A motor driven plunger has been constructed for measuring lifetimes of nuclear excited states in pico second region. An array consisting of six neutron detectors was used to clean up 3'spectra obtained with CS-HPGe detectors. Lifetimes of low excited states in neutron deficient nuclei with low production cross-section e.g. Sly, 77 Kr and 7SRb are reported.

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Fabrication and testing of the recoil mass spectrometer at Bombay Pelletron

Pramana, 2001

A recoil mass spectrometer (RMS) has been designed, fabricated and installed at the 15 AE S beam-... more A recoil mass spectrometer (RMS) has been designed, fabricated and installed at the 15 AE S beam-line of the Pelletron at TIFR. The RMS consists of a quadrupole doublet just after the target chamber followed by an 'electrostatic deflector', a magnetic dipole and a second electrostatic deflector. The recoils produced in the ½¾ C • Ni reaction using 60 MeV ½¾ C beam were focussed with the help of electric and magnetic fields and detected in a strip detector placed at the focal plane of the RMS. Further testing of the spectrometer to obtain mass resolution and efficiency are in progress.

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Fusion cross sections for Li6,7 + Mg24 reactions at energies below and above the barrier

Physical Review C, 2008

Measurement of fusion cross sections for the 6,7 Li + 24 Mg reactions by the characteristic γray ... more Measurement of fusion cross sections for the 6,7 Li + 24 Mg reactions by the characteristic γray method has been done at energies from below to well above the respective Coulomb barriers. The fusion cross sections obtained from these γ-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 (l cr) deduced from the fusion cross sections are found to have an energy dependence similar to other Liinduced reactions.

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Fusion cross sections for theBe9+Sn124reaction at energies near the Coulomb barrier

Physical Review C, 2010

The complete and incomplete fusion cross sections for 9 Be+ 124 Sn reaction have been deduced usi... more The complete and incomplete fusion cross sections for 9 Be+ 124 Sn reaction have been deduced using the online γ-ray measurement technique. Complete fusion at energies above the Coulomb barrier was found to be suppressed by ∼28% compared to the coupled-channels calculations and is in agreement with the systematics of L. R. Gasques et al. [Phys. Rev. C 79, 034605 (2009)]. Study of the projectile dependence for fusion on a 124 Sn target shows that, for 9 Be nuclei, the enhancement at below-barrier energies is substantial compared to that of tightly bound nuclei.

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Experimental study of nuclei in the vicinity of the “island of inversion” through the fusion-evaporation reaction

Physical Review C, 2009

We report the first observation of high-spin states in nuclei in the vicinity of the "island of i... more We report the first observation of high-spin states in nuclei in the vicinity of the "island of inversion", populated via the 18 O+ 18 O fusion reaction at an incident beam energy of 34 MeV. The fusion reaction mechanism circumvents the limitations of non-equilibrated reactions used to populate these nuclei. Detailed spin-parity measurements in these difficult to populate nuclei have been possible from the observed coincidence anisotropy and the linear polarization measurements. The spectroscopy of 33,34 P and 33 S is presented in detail along with the results of calculations within the shell model framework.

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Characteristics of a two-fold segmented Clover detector

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003

The characteristics of a Compton-suppressed, two-fold segmented, Clover detector have been studie... more The characteristics of a Compton-suppressed, two-fold segmented, Clover detector have been studied in singles and add-back modes for using it in the study of heavy-ion fusion–evaporation reactions. The measurements have been performed with standard sources of 152Eu, 60Co and in-beam γ-rays from the fusion–evaporation reaction 28Si on 27Al at Elab=100MeV. Reduction in γ-ray Doppler broadenings due to the two-fold segmentation

Shape changes at high spin in 78Kr

The European Physical Journal A, 2006

High-spin states in 78 Kr have been studied via the 63 Cu(19 F, 2p2n) 78 Kr reaction at a beam en... more High-spin states in 78 Kr have been studied via the 63 Cu(19 F, 2p2n) 78 Kr 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.

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Band crossing in a shears band ofCd108

Physical Review C, 2010

The level lifetimes have been measured for a Shears band of 108 Cd which exhibits bandcrossing. T... more The level lifetimes have been measured for a Shears band of 108 Cd which exhibits bandcrossing. The observed level energies and B(M1) rates have been successfully described by a semi-classical geometric model based on shear mechanism. In this geometric model, the bandcrossing in Shears band has been described as the reopening of the angle between the blades of a shear.

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Search for chiral bands in 133Ce

AIP Conference Proceedings, 2006

Frauendorf [1] suggested an angular momentum coupling scheme for nuclei with triaxial deformation... more Frauendorf [1] suggested an angular momentum coupling scheme for nuclei with triaxial deformation according to which the energy of the valence particles and holes is minimised if their angular momenta are aligned along the short or long axis while the collective (core) angular momentum is aligned along the intermediate axis which is a preferred axis of rotation for irrotational flow-like moment of inertia. The three mutually perpendicular angular momenta couple to a total angular momentum tilted out of the three principal axes planes. This angular momentum coupling can be placed into a right handed or left handed system. The reversal of the direction of the collective angular momentum along the intermediate axis changes the chirality. The consequence of the two possible couplings is the appearance of two bands-called the 'chiral doublet'-with nearly degenerate energy levels having same spins and parity. Recently, a chiral doublet based on three quasi-particle configuration [ν(h11/2)-1 Θ π(h11/2) 2 ] was reported in 135 Nd [2]. This prompted us to search for a chiral doublet in 133 Ce which is an isotone of 135 Nd. The level structure of 133 Ce has been studied through the 16 O + 122 Sn reaction using 80 and 85 MeV 16 O beam from the 14-UD pelletron accelerator in T.I.F.R. Mumbai. The target was prepared by rolling a 1.3 mg/cm 2 thick enriched 122 Sn target foil onto a 15 mg/cm2 thick Au backing. The gamma decay following the reaction was studied using an array consisting of 8 Compton suppressed clover detectors with 14 NaI(Tl) multiplicity filter. The data were collected when three or more clovers fired along with two or more firings in NaI(Tl) multiplicity filter. The decay scheme was studied from the analysis of gamma-gamma coincidence data. The spins of levels and multipolarity of the gamma transitions were obtained from the directional correlation orientation (DCO) ratios, angular distribution and integrated polarization directional correlation (IPDCO) measurements. The partial level scheme of 133 Ce obtained from the present work shows transitions in bands B1, B2 and B3 are in agreement with those reported in refs. [3,4]. Spins and parity of levels in band 2 have been established in the present work. The important feature of our work is the observation of M1 transitions connecting levels in Band 2 to levels in Band 1 and also the E2 transitions from levels in band 1 to band 2. A comparison of gamma energies with increasing spins in bands B1 and B2 shows that there is crossover between spins 27/2 and 29/2. The presence of interband transitions and crossover in gamma energies with increasing spin strongly suggest that bands B1 and B2 form a 'chiral doublet'.

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Structure of dipole bands inIn106

Physical Review C, 2009

High spin states in neutron-deficient 106 In were investigated using 78 Se(32 S, p3n) reaction at... more High spin states in neutron-deficient 106 In were investigated using 78 Se(32 S, p3n) reaction at 125 MeV. The level scheme is extended up to 7 MeV of excitation energy for the negative parity states constituting four dipole bands, and the positive parity states which mainly exhibit single-particle excitations are extended up to 5 MeV. Projected deformed Hartree-Fock calculations were carried out to understand the configurations of different bands in this nucleus.

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Level structures in the 49 107 In nucleus and their microscopic description

The European Physical Journal A, 2009

Excited states of the 107 49 In nucleus were populated through the 78 Se (32 S, p2n) fusion-evapo... more Excited states of the 107 49 In nucleus were populated through the 78 Se (32 S, p2n) fusion-evaporation reaction at beam energy, E lab = 125 MeV. The de-excitations were studied using in-beam γ-ray spectroscopic techniques involving the Compton-suppressed clover detector array. The level scheme of 107 In consisting of about seven bands is established up to spin ∼ 45/2h with the addition of 25 new transitions. Spins and parities of various levels have been assigned through the DCO and polarization measurements. The level structures observed in 107 In have been interpreted in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular-momentum projection techniques. Various bands are reproduced in band mixing calculations with the configurations involving high-Ω πg 9/2 and νd 5/2 orbits, and low-Ω πg 7/2 , νg 7/2 and νh 11/2 orbits. 107 49 In nucleus and their microscopic description using deformed Hartree-Fock and angular-momentum projection calculations. The in-beam spectroscopy of the odd A 103-109 In isotopes has previously been studied by Kownacki et al. [11] and discussed within the framework of the nuclear shell model and the hole-core coupling scheme 46

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