V.R. Pandharipande

V.R. Pandharipande

Abstract The energy of the neutron gas is studied with the Reid and Bressel-Kerman-Rouben soft-core potentials up to a density of 4.5 neutrons fm 3 . Very approximate estimates for neutron gas and solid energies are presented also for the Hamada-Johnston hard-core potential. The short-range correlations are treated by a simple variational method in which the cluster expansion of the energy expectation value, with a Jastrow wave function is truncated at the lowest-order two-body clusters. Healing constraints are introduced in the variation from qualitative comparison with lowest-order Brueckner theory and a differential equation is obtained for the correlation function by minimizing the energy. The effective interaction for use with uncorrelated wave functions, given by this procedure is also interpreted with the Moszkowski-Scott separation method. It is shown that the lowest-order calculations may be reasonable for the Reid and Bressel-Kerman-Rouben soft core potentials, whereas their applicability with Hamada-Johnston hard-core potential is doubtful for ϱ ⪆ 0.7 fm -3 . The results give an approximate equation of state for dense neutron matter and the order of uncertainty in it due to that in neutron-neutron interaction at short range, and may be useful in neutron star structure investigations.

Philip J. Siemens; V.R. Pandharipande

Abstract The binding energy of dense neutron gas is calculated in lowest-order Brueckner theory, and in Jastrow variational theory using the lowest-order cluster expansion of the energy, with a Reid soft-core potential. Subsidiary healing conditions are imposed on the Jastrow correlation function to simulate the Pauli exclusion effects. Due to the soft-core nature of the potential, the defect parameter k is small even at high densities and hence the lowest-order calculation could be a fair approximation. Up to ρ = 0.5 fm−3 the Brueckner and variational calculations give comparable results. Technical complications in applying the Brueckner theory for ρ>0.5 fm−3 are discussed and the results of only the variational calculation are presented for 0.5

V.R. Pandharipande

Abstract The lowest-order variational method with short-range correlations restricted to nearest neighbours is extended to treat the tensor force in nuclear matter. Calculations based on the soft-core Reid potential give −9.8 MeV binding energy per nucleon at equilibrium k F = 1.43 fm −1 . The nuclear matter results from k F = 0.7 to 1.8 fm −1 are in very close agreement with those of the Brueckner-Bethe calculations.

V.R. Pandharipande; K.G. Prasad; R.P. Sharma; B. V. Thosar

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.

Girish Chandra; V.R. Pandharipande

Abstract The energy levels of Te 125 have been studied by detailed gamma gamma coincidence measurements. Two new weak gamma transitions of energies 80 ± 5 keV and 120 ± 5 keV have been observed in coincidence with the 176 keV gamma transition. A new energy level has been introduced at 401 keV. There is evidence of a weak gamma transition of 62 keV between levels at 524 keV and 462 keV.

V.R. Pandharipande

Abstract The parameters of density-dependent effective interaction suggested by Bethe are determined from restricted Hartree-Fock calculations in 4 He, 16 O, 40 Ca and infinite nuclear matter. The parameters of an equivalent momentum-dependent interaction are also studied. It is shown that the contributions of the proposed density-dependent interaction to the binding energy of nuclear matter closely resemble those of the Reid potential. The distribution of neutron and proton densities in 40 Ca, 120 Sn and 208 Pb is studied with this interaction by a variational method using local density approximation. The calculated binding energies, radii, central densities and surface thickness are in good agreement with the experimental data.

V.R. Pandharipande

Abstract A modified δ-function, effective, residual interaction is proposed for nuclear, shell-model calculations. The interaction V 12 is defined as follows: 〈j 1 j 2 J|V 12 |j 3 j 4 〉 = a J 〈j 1 j 2 J|Vδ(r 1 −r 2 )[1−β+β(σ 1 ·σ 2 )]|j 3 j 4 J 〉, α J = 1 if J ≠ j 1 ±j 2 , J ≠ j 3 ±j 4 , α J = a+bJ if J = j 1 ±j 2 or J = j 3 ±j 4 . Calculations with this interaction are presented in 18 O, 33 Cl, 42 Ca, 54 Fe, 90 Zr, 92 Nb, 92 Zr and 210 Bi. The interaction gives good agreement in all these isotopes with the following values of the parameters: V = 1630 MeV · fm 3 , β = 0.01, a = 0.42, b = 0.05. Calculations in even tin and odd indium isotopes are also presented.

V.R. Pandharipande; K.G. Prasad; R.P. Sharma

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.

V.R. Pandharipande; K.G. Prasad

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.

V.R. Pandharipande

Abstract We show that the interaction energy of a nuclear system interacting with a central Yukawa plus a velocity-dependent δ-function two-body interaction can be reasonably approximated as a function of the local densities. The resulting expressions bear general resemblance with the Weiszsacker semi-empirical mass law. A simple variational calculation is carried out with these expressions for the 4 He, 16 O, 40 Ca and 56 Ni nuclei and nuclear matter. The calculated binding energies and radii are in excellent agreement with the experimental data.