K.G. Prasad

Internal conversion studies of the 2+ → 0+ transitions in some deformed even nuclei

Abstract The K conversion coefficients of 2 + → 0 + transitions in some deformed even nuclei have been determined with the help of β-γ, X-γ and γ-γ coincidence measurements. All possible uncertainties in these measurements have been minimised and properly evaluated. The α K values for 2 + → 0 + transitions in Er 166 , Yb 170 , Hf 176 , W 186 , Os 186 , Os 188 and Dy 160 are found to be 1.67, 1.31, 1.10, 0.55, 0.42, 0.34 and 1.52, respectively. These values are in agreement with the theoretical ones within an experimental error of about 6%. Large deviations of the order of 15 to 20% as reported by earlier workers are not observed.

Level structure of 117In from the decay of 117Cd

The levels in 117 In populated in the decay of ≈ 2.7 h 117 Cd and 117m Cd have been studied using a Ge(Li) detector and scintillation techniques. In all 45 gamma rays have been identified. A total of 23 energy levels extending up to 2461 keV has been proposed on the basis of the gamma-gamma and beta-gamma coincidence measurements. The K-conversion coefficient of the 88 keV transition is measured to be 1.3±0.3. The gamma-gamma directional correlations of 1028-1068 keV and 567-1430 keV cascades have been found to be W(θ) = 1-0.022(±0.012)P 2 (cos θ)+0.015(±0.038)P 4 (cos θ) ,W(θ) = 1-0.011(±0.012)P 2 (cos θ)+0.060(±0.038)P 4 (cos θ). The beta-gamma differential correlation of the beta group feeding the 748 keV level and the following 433 keV gamma ray is found to be isotropic. The levels at 660, 748, 881, 1249 and 1715 keV have been identified as the members of a possible K = ½ + rotational band. The levels at 860, 950, 1056, 1068 and 1430 keV have been suggested to be the members of a (½ + proton hole + 2 + core) multiplet. The possible nature of the other higher-excited states has been discussed.

Fission lifetimes measured by crystal blocking of fragments from 238U(n, f) reactions

The lifetime of 239U compound nuclei formed in 238U(n, f) reactions has been measured at three neutron energies, 1.7, 2.3, and 3.6 MeV, by the crystal-blocking lifetime technique. The results are τ = 300 ± 70 as (1.7 MeV), τ = 200 ± 55 as (2.3 MeV), and τ < 100 as (3.6 MeV). For the two lower energies, the axial and planar methods for lifetime extraction have been compared and the results are in reasonable agreement. The lifetimes are combined with measured values of the fission probability Pf = ΓfΓ to obtain the partial widths for fission, Γf, and for neutron emission, Γn. These are in turn compared with theoretical estimates.

Nuclear levels of 199Au

Abstract The low energy level scheme of 199Au as observed in the decay of 30 min acitivity of 199Pt has been studied using an intermediate image beta ray spectrometer and scintillation coincidence spectrometers in conjunction with a 512-channel analyser. Four beta groups of end-point energies at 1690±50, 1370, 1150 and 900 keV have been identified. The gamma-rays of energies 75, 197, 245, 320, 475, 540, 715, 790 and 960 keV were observed in the scintillation spectrum. To explain the various β-γ, γ-β and γ-γ coincidences and their relative intensities, levels at 75, 320, 475, 540, 737, 790 and 960 keV have been proposed. This new level scheme of 199Au shows a close similarity with those of neighbouring odd-mass gold nuclei. An isomeric state at about 475 keV has been identified, also suggesting a possible existence of the h 11 2 state in the 199Au nucleus.

Further studies on the decay of Eu156

Abstract The beta decay of Eu 156 has been studied by means of an intermediate image magnetic spectrometer modified for the beta-gamma coincidence studies. An attempt has been made to detect the possible beta feeding to the lowest energy level of the beta vibrational band which is expected in the deformed Gd 156 nucleus. The present study does not give any definite indication of feeding of such a level in the decay of Eu 156 and if it exists it should be less than 0.1%. The energy and intensity of different beta groups and various gamma-rays in this decay are given.

Magnetic moment of the 660 keV state in 117In

Abstract The g-factor of the 3 2 + 660 keV state in 117In was measured by the differential-delay, constant-angle method. The observed values of the g-factor and the magnetic moment are +0.63±0.05 and +0.95±0.08 μN, respectively. They are compared with the values predicted by the models for spherical and deformed nuclei.

Decay of Pt197m

Abstract The decay of 86 min Pt197m has been investigated with scintillation coincidence spectroscopy using a 512-channel pulse-height analyser. The Pt197m isotope was produced by neutron irradiation of enriched Pt196. The 346 keV isomeric transition has been found to be in coincidence with a gamma ray of energy 50±3 keV. This established the presence of an intermediate level between the 13 2 + isomeric state and the 1 2 − ground state of Pt197. The K conversion coefficient of the 346 keV transition has been estimated to be 4.8±1.5 which agrees with an M4 multipolarity for that transition and a 5 2 − assignment for the intermediate level. The total conversion coefficient of the 50 keV transition shows it to be E2 in character. A beta branching to the well-known 409 keV isomeric level in Au197 has been established by milking the 7s Au197m from Pt197m. The branching ratio of beta transition is estimated to be 4% from the relative intensities of the 346 keV gamma ray of Pt197m and the 279 keV gamma ray of Au197m.

Self-consistent nuclear single-particle Hamiltonian

Abstract The Thomas-Fermi theory of nuclei has been extensively used to define a single-particle Hamiltonian for nuclei. This Hamiltonian is solved self-consistently by a Hartree type iterative procedure. The single-particle energies and the rearrangement effects are discussed. The results for 40 Ca are compared with those obtained with restricted Hartree-Fock calculations in harmonic oscillator approximation.