Table of contents

The authors use a simple and physically plausible model to evaluate the bubble contribution to the quark sea. With acceptable values for the free parameters they find agreement with the limited data and predict the suppression of heavier quark seas. They also find a transverse momentum distribution which rises with x. The model suggests that the length of the confinement region rises linearly with quark energy.

The authors discuss the various methods for taking into account the centre-of-mass correlations in the hadron-nucleus elastic differential cross section. From a model-independent analysis, they find that the uncertainties induced by various prescriptions have no drastic effects on the extraction of densities from scattering data when the analysis is restricted to the forward-angle region.

Present measurements of the energy spectrum of cosmic-ray electrons appear to show an increase of exponent of approximately=1.5 between energies below 1 GeV and above 10 GeV. This change is much greater than expected if there is an exponential path-length distribution of galactic cosmic rays. Agreement can be restored if allowance is made for the loss of short transit times in the lifetime distribution of particles in the interstellar medium such as is favoured for nuclei by the work Shapiro and Silberberg and, more recently, by Garcia-Munoz et al.

By re-identifying some of the vector meson states which have been recently observed coupling to e⁺e^-, the authors show that in all flavour sectors the spectra of radial excitations can be well described by a Klein-Gordon-type wave equation employing a simple, linear qq potential. The wavefunctions obtained by solving the equation are coupled with quark-pair creation hypothesis to predict a number of hadronic branching ratios of the light-quark, radially excited states. The suppression of large phase-space decays of the excited states is understood.

Detailed calculations in the frame of a potential model fitted precisely to the low-energy neutron-proton (deuteron and scattering) experimental data show that the corrections introduced into measurable quantities by electromagnetic interactions are relatively as important as the hadronic contributions from nucleon isobars. The unknown behaviour of the nucleon electromagnetic form factors at high momentum transfers affects only the details of the comparison, at least when constraints provided by current quark-parton models are imposed. But the ignorance of the explicit value of the nucleon hadronic mass is found to generate, in attempts at phenomenological extraction from the data of hadronic values for the np physical quantities, uncertainties as large as the contributions from the isobar channels themselves.

Two parameters of the spin-orbit part of the deformed Woods-Saxon potential, namely the strength parameter lambda and the radius parameter (r₀)_so, were adjusted to reproduce the spins and parities of even-odd and odd-even nuclei in the range 51<or=Z<or=83 and 61<or=N<or=127. Experimental evidence for the values of the nuclear deformation parameters beta ₂ and beta ₄ was taken into account. The parameters lambda and (r₀)_so were subjected to smooth variations in order to preserve the overall character of the single-particle spectrum and not to disturb the sequences of spins and parities of the neighbouring nuclei. The choice of the spin-orbit potential parameters for transitional nuclei is based essentially on the interpolation between the corresponding values for spherical and well deformed nuclei for which interpretation of the experimental data is more certain.

The ground-state of odd-mass nuclei are studied within the framework of the core-particle coupling model. The space of core states includes both the ground state and beta bands. Energies and electromagnetic transition probabilities are investigated for the cases ¹⁵⁵Gd, ¹⁵⁷Dy and ¹⁷⁵Hf. Reasonably good agreement with experiment is found.

Semiclassical concepts have been used to obtain a formula for determining angular distributions for heavy-ion transfer reactions starting from the expression of the transition matrix in DWBA. The distorted waves are expanded in partial waves and the radial wavefunctions approximated by the WKB approximation. Further approximations enable one of the partial-wave summations to be performed analytically. The transfer matrix elements occurring in the resulting formula has been simplified to a one-dimensional integral by assuming a straight-line orbit for the relative motion. As an illustration, angular distributions have been calculated for the reactions ²⁶Mg(¹¹B,¹⁰B)²⁷Mg and ²⁶Mg(¹¹B,¹⁰Be)²⁷Al at 114 MeV laboratory energy and compared with experiment. The agreement is good.

The g factor of the 5.106 MeV 2^- state of ¹⁴N has been measured by the recoil distance technique. The perturbation of the nuclear alignment in one-electron ions was observed time-differentially following the ³He(¹²C,p)¹⁴N reaction in a ³He-implanted target. From the observed hyperfine frequency, the nuclear g factor was deduced to be mod g mod =0.66(4). The lifetimes of the 5.106 MeV 2^- state ( tau _m(2^-)=6.2(4)ps) and the 5.832 MeV 3^- state ( tau _m(3^-)=13.7(11)ps) were measured, also by the recoil-distance technique, using the reaction ¹²C(³He,p)¹⁴N. The former result is significantly different from the published value.

Forward-angle data for the ⁶⁴Zn(⁷Li,⁶He)⁶⁵Ga reaction at 36 MeV show the spins of the 62 and 1663 keV levels to be ¹/₂^- and ³/₂^- respectively. Levels at 1369 and 2210 keV are most probably of f_7/2 character.

Reactions ⁶⁴Zn( alpha ,p gamma )⁶⁷Ga and ⁵³Cr(¹⁶O, pn gamma )⁶⁷Ga populated the levels in ⁶⁷Ga. Gamma-gamma coincidence experiments were carried out at E_alpha =13 and 15 MeV with the ( alpha ,p gamma ) reaction and E_(16)O=42 MeV with the heavy-ion reaction. The Doppler-shift attenuation method was used with the ( alpha ,p gamma ) reaction to deduce mean lifetimes (or limits) for certain levels, along with the recoil-distance method utilised both in singles and gamma - gamma coincidence with the heavy-ion reaction. A mean lifetime of tau _m=60+or-30 ns for the first excited state at 167 keV was measured using the delayed coincidence method. Gamma-ray angular distributions and linear polarisations were measured at E_alpha =13.5 MeV using a Ge(Li)-NaI(Tl) escape-suppressed spectrometer and a three-Ge(Li) Compton polarimeter and analysis resulted in spin and parity assignments. Transition strengths were calculated and the results are discussed in terms of the particle-cluster-vibrational-core coupling model.

The level structure of ⁷⁹Se has been studied by the ⁸⁰Se(p,d) reaction with 22.9 MeV incident protons. Thirteen excited energy levels up to 2.0 MeV have been identified. The angular distributions for twelve of the observed transitions are compared with distorted-wave Born approximation calculations. Angular momentum transfers are determined and spectroscopic strengths are deduced from the data. The results are compared with the predictions of the Coriolis coupling with the residual pairing-force model of Heller and Friedman (1974).

The odd-odd nucleus ¹⁰⁶In has been studied following the decay of ¹⁰⁶Sn, using high-resolution gamma-ray spectroscopy. Spin and parity assignments of 1⁺ have been established for two of the six excited states observed in ¹⁰⁶In, and log ft values for the beta ⁺/EC population of these 1⁺ states indicate the presence of large components of the ( pi g₉2/^-1, nu g₇2/)¹⁺ two-quasiparticle configuration in their wavefunctions.

The level structures in ¹⁷³W and ¹⁷⁵W have been studied using (¹⁶O,4n) reactions. Rotational bands based on three different single-particle configurations are observed to high spin in each nucleus. From a comparison of their contrasting behaviour with the ground-state rotational bands in ¹⁷²W and ¹⁷⁴W, it is concluded that the decoupling of a pair of i_13/2 neutrons causes the backbending in ¹⁷⁴W. A single-quasiparticle Coriolis mixing calculation is able to reproduce the observed band structure up to high spin.