Table of contents

Using a liquid-drop-model fission path and the two-centre shell model, the authors calculated static fission mass yields for ²⁵³Fm(n,f), ²⁵⁴Fm(sf), ²⁵⁵Fm(n,f), ²⁵⁶Fm(sf), ²⁵⁷Fm(n,f), ²⁵⁸Fm(sf), ²⁵⁹Fm(n,f) and ²⁶⁰Fm(sf). For a particular choice of the length of the fissioning nucleus, the change from asymmetric to symmetric distributions and the gross features of the mass yield curves are reproduced. They predict highly asymmetric events that should be seen primarily in the thermal-neutron-induced fission of the lighter isotopes mentioned.

The integral energy spectrum of all primary cosmic-ray particles in the energy range 50-10⁶ GeV presented by Grigorov et al. (1970, 1971) in a series of proton satellite experiments has been used to derive the differential energy spectrum of primary cosmic-ray nucleons with the help of the recent knowledge of the mass composition of primary cosmic rays. It is found to be represented by the form D(E_N)=2.06E_N^-2.70cm^-2 sr^-1 s^-1 GeV^-1 over the nucleon energy range 50-10⁴ GeV. This form D(E_N)=2.54 E_N^-2.60, suggested by Hoock and Turver (1974) from the experimental results of Grigorov et al. and used extensively by Bhattacharyya and his collaborators (1977) to derive the secondary cosmic-ray spectra, is not justified.

It is argued that a three-rung ladder graph in scattering on nuclei with A>2 should be important for peripheral interactions. Its singularity curves are evaluated and discussed for the case of pion-nucleus scattering in the Delta resonance region.

Presents a simple model for non-diffractive axial vector meson production at intermediate energies. Data on the analogous pseudoscalar production processes are used to predict the production properties of the A₁(J^PC=1⁺⁺) and B(1^+-) SU(3) nonets. A unitary, coupled-channel formalism then allows one to predict the s, t and m² dependence of the Q-like enhancements which are observed in the K rho and K* pi channels produced in charge and hypercharge exchange processes. Detailed predictions for forthcoming experiments are made. Existing data are in qualitative agreement with the model.

A domain of allowed values of the KN Lambda and KN Sigma coupling constants is constructed by applying the maximum modulus theorem and a factorisation theorem and making use of the data on the modulus of the K^+or-p forward scattering amplitude on its cuts. It is shown that there is a strong correlation between the positions of the zeros of the amplitude and the strengths of its poles, so that information on the zeros provides further restrictions on the coupling constants.

Angular distributions of cross sections and vector and tensor polarisations for pi d to pi d are calculated at T_lab^pi =142, 180 and 256 MeV. The isospin-one dibaryon resonances ¹D₂, ³F₃ and ¹G₄ are mixed into Faddeev partial waves. Using experimental differential cross sections as constraints, dibaryon signals in the polarisation observables are calculated for a range of possible resonance parameters.

It is pointed out that (i) the nucleon-nucleon-boson coupling constants obtained in the framework of the OBEM show the applicability of the OZI rule for the low-energy nucleon-nucleon interaction and (ii) the number of bosons exchanged simultaneously is limited by the OZI rule.

Charge-dependent residual nuclear forces are shown to arise from the coupling of the discrete states to the surrounding continuum. Shell and other nuclear structure effects in the charge dependence are discussed. The trends obtained are compared with those observed in the Coulomb displacement energies as well as in the isospin-non-conserving particle decay widths. The problem of the radii of nuclear charge distributions is discussed.

A semiclassical approximation to the Hartree-Fock approach is applied to extract the smoothly varying part of the total energy of a rotating nucleus. By introducing the Wigner distribution function, explicit expressions for the total energy, angular momentum and density distribution are calculated in a systematic way. Numerical calculations within the framework of an extended Thomas-Fermi model show that the smooth quantum corrections are relatively small. The self-consistency aspects of the semiclassical description are discussed.

It is pointed out that first-order nuclear matter calculations with effective interactions must satisfy the Hugenholts-Van Hove theorem and that this tells us nothing about the validity of the interaction itself. Unawareness of this fact has given rise to incorrect statements and misleading conclusions in the literature which this paper points out and rectifies.

The l=0 to 5 phase-shifts have been obtained from a microscopic calculation for the elastic scattering of neutrons from the nucleus ¹²C for centre-of-mass incident energies in the range 0 to 17 MeV using the resonating group method. A shell-model wavefunction of the ¹²C ground state consisting of 19 Slater determinants has been used and the nonlocal interaction between the neutron and ¹²C has been calculated using the complex generator coordinate technique. The differential cross sections for incident centre-of-mass energies 0.46, 4.2. 6.4. 6.69 and 13.4 MeV, at which no sharp resonances for the n+¹²C system exist, have also been calculated and are found to be in fair agreement with the experimental data.

The synthesis of elements 103, 105 and 107 through heavy-ion reactions is discussed in the context of the fragmentation theory by estimating the production cross sections with the help of the statistical model, including fission competition. It is shown that the most favourable target-projectile combinations predicted by theory coincide with the ones already used in experiments to produce transfermium elements, provided that the critical angular momentum value is determined by the condition that the fission barrier vanishes.

The yrast states up to J^pi =20⁺ of four even hafnium isotopes ^166-172Hf are studied in a microscopic formalism of variation after angular momentum projection with number conservation in each state. The nuclear Hamiltonian employed in the calculations consists of the quadrupole-plus-pairing interactions. The computed energy spectra and B(E2) values are in good agreement with the corresponding experimental data.

The properties of neutron-deficient mercury nuclei have been investigated in a Hartree-Fock calculation with a surface delta interaction. The ground and low-lying excited states of these nuclei are seen to be of oblate shape. An angular momentum projection and band-mixing calculation for ¹⁸⁹Hg gives two low-lying bands which agree reasonably well with experiment. State-dependent neutron effective charges are needed to obtain agreement with experimental B(E2) ratios.

The g-factor of the 0.74 MeV ⁵/₂⁺ state of ¹⁵C has been measured by observing the hyperfine modulation of the gamma -ray anisotropy in one-electron ions recoiling into vacuum following the reaction ³H(¹³C,p)¹⁵C*. From the spatial frequency determined as a function of recoil distance the g factor was deduced to be mod g mod =0.703(12). The shell-model interpretation of this result is discussed.

The reactions ⁵⁰Ti(t,d)⁵¹Ti and ⁵⁴Fe(t, d)⁵⁵Fe have been studied in the sub-Coulomb regime at triton energies in the range from 2.25 to 3.50 MeV. Values of the RMS radius of the 2p_3/2neutron orbit in the ground states of the final nuclei were determined from a DWBA analysis of the measured absolute cross sections. In the DWBA analysis of the (t,d) data the spectroscopic factors which were used were those which resulted from a sum-rule analysis involving published neutron stripping and pick-up data. The results of the present experiments when taken with the results of similar experiments on targets of ⁴⁸Ca and ⁵²Cr establish the variation of 2p_3/2 neutron orbit size within the isotonic sequence of N=29 ground states.