Table of contents

A national nuclear structure facility (NSF) incorporating a large tandem accelerator is under construction at Daresbury Laboratory in UK. A description of the accelerator and its main components is presented together with the results of the first stage of electrostatic testing. Some details of major pieces of experimental equipment also are reviewed.

Quasiparticle-core-coupling in odd-mass transitional platinum nuclei is studied. The theoretical procedure amounts to solving a combined set of equations of motion for stripping (particle-like) + pick-up (hole-like) amplitudes, relating the triad of nuclei [A], [A + 1] and [A + 2]. We adopt the solution method of Dönau and Frauendorf and assume a coupling via the schematic pairing + quadrupole interaction fields. No attempt at selfconsistency is made; we precalculate the various moments ⟨R||Q₂||R'⟩ for each core nucleus assuming various core models and set for simplicity all pair moments relating the core nuclei [A] and [A + 2] equal, _A+2⟨R||P^†||R⟩_A = Δ/G. The dependence on the core description is investigated by comparing predictions of the Dynamic Deformation Theory for high-spin positive parity states in the prolate-oblate transitional nucleus ¹⁹¹Pt with predictions of the 30°-rigid-rotor and γ-unstable Wilets-Jean model. From an inspection of energy sequences we conclude that there is no decisive favouring of any core model. The quality of the prediction with DDT-cores is, however, sensitive to the differences in the DDT-matrix elements for the two cores. Calculations of transfer strength patterns, in particular for pick-up to 13/2+ states, exhibit more sensitivity to the core-description employed. Comparison with pick-up data for ^{189,191,193,195,197}Pt is made.

It is demonstrated that the Interacting Boson Model I (IBM), which is described by a Hamiltonian of six coupled harmonic oscillators, (one s-boson and 5 d-bosons), where the total number of bosons, N, is constant of the motion, can be transformed into a Bohr-Mottelson model (BMM) described by a Hamiltonian with the familiar five dimensional quadrupole oscillator degrees of freedom. The correspondence is one-to-one for a BMM acting in a sub-space of the full five-dimensional harmonic oscillator space. The proof depends on a well-known non-linear realization of the generators of SU(6) (which are the basic building blocks of the IBM) in terms of the five BMM bosons and the number N. The orthonormal basis vectors of the BMM are obtained. The relationship between the limiting symmetries of the IBM and the geometrically simple limits of the BMM is described with the aid of the concept of potential energy surface. The form of the BMM Hamiltonian is given for the adiabatic limit. Finally we show that previous work on this problem involving coherent states and the generator coordinate method is incomplete.

Aligned two-quasiparticle bands in ¹⁵⁶Ho and ¹⁶⁰Dy have been discussed. In ¹⁵⁶Ho a strongly decoupled system apparently belonging to the [h_11/2]_p° [i_13/2]_n configuration has been located with the ¹⁴⁶Nd(¹⁴N, 4n) reaction. Previously, four levels at 1607, 1723, 1974 and 2577 keV in ¹⁶⁰Dy were populated strongly in the (³He, α) reaction and were assigned as possible members of a superband. These levels are discussed, and a comparison of the aligned bands in the odd-odd and even-even systems is performed.

The effect of using a realistic triton wavefunction and a consistent transfer interaction on the magnitude of the two neutron transfer cross-sections in (p, t) reations is surveyed. The results of DWBA analyses of ²⁰⁸Pb(p, t)²⁰⁶Pb and ¹⁸O(p, t)¹⁶O reactions with the triton wavefunction of Strayer and Sauer are presented. More complete analyses which also include a realistic two neutron overlap function with the extended basis shell model method of Feng et al. on the reactions ¹⁸O(p, t)¹⁶O, ⁴⁸Ca(t, p)⁵⁰Ca and ⁹⁰Zr(t, p)⁹²Zr are presented. The latter show an excellent agreement between the theoretical cross-sections and experiment implying that DWBA provides a satisfactory description of these reactions.

The energy spectrum of ¹⁶³Er has been calculated within the particle-rotor model. Two approximations for the intrinsic motion have been studied: the BCS and the diagonalization method. It is shown that the positive parity i_13/2 decoupled band can be reproduced using the diagonalization method without an ad-hoc attenuation factor.

Calculations both of the Pauli Principle effects in elastic scattering and of the nucleon-transfer channels involve channel states that are not mutually orthogonal and normalised. A unified treatment is given for the non-orthogonalities from either source, resulting in a non-local residual potential that is explicitly Hermitian, independent of the incident kinetic energy, and cumulative in the number of exchange configurations.

We describe a method to include the Coulomb interaction in Glauber calculations for elastic proton-nucleus scattering. We show that at 800 MeV the polarization is sensitive to the electromagnetic spin-orbit interaction in a wide angular range. We also show that if the charge distribution is approximated by a uniformly charged sphere serious errors may appear for large momentum transfers.

The absolute oscillator strength, f, was measured for the spectral line λ = 451.966 nm of gadolinium by means of the absorption method with the atomic beam acting as an absorbant. The absolute value of f which was obtained is f = 0.28 ± 0.07.

The ¹S₀ level in the 5p⁴ ground configuration of Xe III has been revised. Parameter values for the 5p⁴ configuration have been determined by parametric fitting and the eigenvectors used to calculate transition probabilities for magnetic dipole as well as electric quadrupole transitions within the 5p⁴ configuration. An improved value for the ionization potential of Xe II is used to determine the energies of the 4d¹⁰5s²5p⁴¹D₂- 4d⁹5s²5p⁶²D_5/2 (N₅O_2,3O_2,3 (¹D₂)) and 4d¹⁰5s5p⁵¹P₁-4d⁹5s²5p⁶²D_5/2 (N₅O₁O_2,3 (¹P₁)) Auger transitions in Xe, which are commonly used as reference lines in photoelectron spectroscopy.

Equations describing the evolution of phase and energy of a particle at cyclotron resonance in a magnetic field growing in time are obtained. It is seen that, at adiabatic variation of the magnetic field, the autoresonance is realized not only at weakly relativistic but also at ultrarelativistic energies. The upper limit of achievable energy is related to the synchrotron radiation losses.

We show the existence of a new instability mechanism of a current-carrying plasma, which, for a sufficiently long system, may occur after saturation of the two-stream instability. The instability is due to combined asymmetry and nonuniformity of the electron distribution and is manifested by the spontaneous appearance of a growing, localized Langmuir oscillation at approximately the position v_d = v_t. A possible connection with the formation of double layers is pointed out.

Results of the investigations of the spectral characteristics of electroluminescence of SrS:Cu, Er, BaS:Cu, Er and SrSe:Cu, Er phosphors are presented. Some new features of the voltage and frequency dependence of EL-emission are reported.