Table of contents

Available measurements of the transitions 2s²-2s2p and 2s2p-2p² are examined as to their iso-electronic consistency by studying appropriate functions of the transition energies of 2s²¹S₀-2s2p¹P₁, ³P₁, 2s2p¹P₁-2p²¹D₂, ¹S₀ and 2s2p³P₂-2p²³P₂, and by deriving semi-empirical screening formulae for the fine-structure intervals of the ³P terms. In this way, accidental experimental errors are smoothed out and missing data are determined by interpolation. The results of the analysis are comprised in a table of recommended level values, extending to Z = 26 or, for 2s2p¹P₁, ³P₁, to Z = 28. A comment on our recent discussion of the Li I-like spectra is appended.

Energy levels are presented for Ni XX and Cu XXI of the fluorine isoelectronic sequence. Behaviour of the energy structure of Fe XVIII through Zn XXII, Ge XXIV and Se XXVI was observed along the isoelectronic sequence. The spectra were obtained from laser-produced plasmas.

Hyperfine structure of the transition 5d⁴D_7/2-6p⁴P⁰_5/2 in Xe II is measured for the isotopes ^129,131Xe, and h.f.s. coupling constants A and B are evaluated for the 6p⁴P⁰_5/2 level. Isotope shifts in the same transition are measured for ^{128,129,130,131,134,136}Xe relative to ¹³²Xe utilizing Lambdip technique in a beam-laser experiment. The field shifts are evaluated yielding relative changes δ ⟨r²⟩ of mean-square charge radii.

The spectrum of five times ionized sulphur has been studied in the wavelength region 100-8000 Å by means of a sliding spark in vacuum. About 90 lines are now attributed to the system, some 70% of which are classified for the first time. The ionization energy, 710 194.7 cm^-1, derived from a polarization formula based on f, g and h terms is in accordance with Ritz formulae applied to the ns, np and nd series.

Some practical methods are suggested for applying the Arbitrarily Normalized Decay Curve (ANDC) method for cascade-correction in beam-foil lifetime measurements. These methods are used to analyze decay curves recorded for the ns²S-np²P⁰ resonance doublet in Ar VIII, Kr VIII and Xe VIII by including the np²P⁰-nd²D cascade transitions in the analysis. The f-values derived from the np lifetimes for the ns-sp multiplet are in good agreement with recent theoretical estimates for Ar VIII and Kr VIII and agree with theory for Xe VIII within the combined experimental and theoretical uncertainties.

The absorption spectrum of Au I, in the 960-2100 Å region, has been observed and analysed.

The atomic vapours have been produced with both an induction heated furnace and with flash-pyrolysis.

One hundred and thirty new lines have been observed, 101 of which have been classified in fifteen new series corresponding to transitions 5d¹⁰6s²S-5d⁹6snp, nf and converging to the first four limits above the first ionization limit.

Some of the remaining new lines have been interpreted as due to transitions from the metastable state and some other due to transitions of double-electron excitation.

The relative value of the photoionization cross section has been measured in the 950-1350 Å region as well as the Fano parameters for the three strongest lines broadened by autoionization.

The magnetic moment of the second excited (5/2^-; 136 keV) state in ⁵⁷Fe was measured in a time differential perturbed angular distribution (TDPAD) experiment. The nucleus was excited in the reaction ⁵⁷Fe (p, p')⁵⁷Fe* with a pulsed proton beam. With use of the known internal magnetic field for Fe in Fe a magnetic moment of μ = + 0.935(10) nm was deduced from the observed Larmor-precession frequency.

The article presents a method of calculating analytically the yield pattern and the spin distribution of the nuclei formed as end products after deexciting a set of nuclei by particle evaporation and gamma emission. Some results from comparisons with experimental spallation data are given.

A new wire-loaded nuclear emulsion 4π detector has been used to study multiplicities and angular distributions of charged particles produced in 340 MeV/nucleon Ne + W interactions. The spectra are compared to predictions from a simple thermal spectator-participant model in which we assume the particle emission to originate exclusively from three ideal nucleon gas systems in equilibrium. The shapes of the inclusive experimental angular spectra are in good agreement with the predictions, while the multiplicity of grey prong producing (high energy) particles is slightly overestimated by the model. A much more poor agreement is found for high multiplicity events alone under the assumption that these are central reactions.

With the aid of experimental data on the inelastic scattering of high-energy electrons from ¹²C, transition densities have been estimated for the 2⁺ level at 4.44 MeV, the 0⁺ level at 7.65 MeV and the 3^- level at 9.64 MeV in ¹²C. The transition densities were calculated in the particle-hole formalism with radial wave functions generated from a Woods-Saxon potential. The calculations exhibit a large sensitivity to the unbound states and indicate that the transition (1p_3/2)^-1-1g_9/2 is important for the 3^- level.

Modulation characteristics of volume holographic gratings stored in KCI:Ca crystals utilizing the F → Z₁ colour centre conversion have been studied. By means of the Hurter-Driffield curve the absorption and refractive index modulation amplitudes have been determined at the optimum working point. Further, the experimental and calculated diffraction efficiency values obtained by using two dissimilar solutions of the coupled wave equations are given.

As a first step towards an understanding of the reactivity of metals and their ability to break chemical bonds we have performed self-consistent calculations on a model with H₂ standing upright on a jellium surface. Data for the adsorbate-induced electron structure and potential-energy curves with substrate parameters characteristic for Al, Mg and Na are presented. We extract concepts and trends that should be useful for other molecule-metal systems as well, e.g.,

(i) the downshift of the antibonding affinity level, in a symmetry-affected correlation with the effective electron potential of the clean surface,

(ii) the filling of the corresponding molecular resonance, localized primarily on the outer H atom,

(iii) the thereby weakened intramolecular bond, and

(iv) the natural separation of the molecular chemisorption energy into intra- and extramolecular terms, whose relative size determines the molecular adsorption to be dissociative, activated etc. The model calculations provide illustrations of different classes of molecular chemisorption systems and support the Lennard-Jones description of molecular adsorption, provided that the molecular potential-energy curve is due to chemical rather than van der Waals' forces.

An analysis is presented of the production and decay of ρ⁰(770) and f(1270) in π⁺p interactions at 8 GeV/c. Differential cross-section and density matrix elements are given and compared with previous data. In the ρ⁰ production, both central production and fragmentation of the beam π⁺ are important mechanisms, whereas the f mesons are found to be produced dominantly through beam fragmentation at 8 GeV/c. A comparison of the reactions π⁺p → ρ⁰ + X⁺⁺ and K^-p - *⁰ (890) + X⁰, in terms of the density matrix elements of the ρ⁰ and the *⁰, reveals an interesting similarity between these reactions. In the Regge-exchange region pseudoscalar exchange dominates both in the reaction π⁺p → ρ⁰ + X⁺⁺ and in the reaction π⁺p → f + X⁺⁺. A single term triple-Regge formula gives a good parameterisation of the pseudoscalar exchange part in the reaction π⁺p → ρ⁰ + X⁺⁺.

Recent results on high energy neutrino physics are reviewed in order to demonstrate how the quark concept facilitates our understanding of the structure of the nucleon and neutrino physics.

Unification of the electromagnetic force with the weak (within the context of the SU(2) × U(1) theory), unification of the strong force with the electroweak (within the context of Grand Unification schemes) and unification of gravitational quanta with leptons, quarks, Yang-Mills quanta and Higgs particles (within the context of supergravity theories) is reviewed.

The history of the reaction in which a lepton pair is produced in hadronic collisions is reviewed. We then outline the experimental approach and the results with particular attention to the production of new resonances, the upsilon family near 10 GeV. The interpretation in terms of a new heavy quark is rationalized. Finally, the information obtained from the non-resonant continuum of dilepton masses is detailed. It is seen that we obtain detailed information on the quark structure functions and provide incisive tests to the new theory of strong interaction.

I discuss a new method of analyzing low energy hadron-hadron scattering designed to reveal internal quark-gluon eigenstates.

The production of the Y(9.46)- and Y'(10.02)-resonances in e⁺e^--annihilation has been observed in three, respectively two, different experiments at DORIS. The observed leptonic decay widths are consistent with Y and Y' being the ground and the first excited state of a bound b system, where b represents a heavy quark with charge - 1/3. The event topology at energies outside the Y resonances clearly exhibit 2-jet structure in good agreement with the quark parton model. The characteristics of the Y direct hadronic decays are consistent with the 3 gluon model.

In this talk, charmed mesons D⁰, D⁺ and F⁺ produced in e⁺e^- annihilation are discussed. The emphasis is on the most recent results. In particular preliminary performance characteristics and results from the new SLAC-LBL Mark II detector at SPEAR are presented.

The ideas of color and the chromodynamic forces are reviewed. We discuss the current ideas on confinement via chromoelectrical forces and the perturbative aspects of QCD. The main tests of chromodynamics in lepton-hadron scattering, hadron-hadron scattering and e⁺e^--annihilation are described.

Deep inelastic charged lepton scattering has provided the main experimental evidence that the nucleon contains constituents which behave like point-like particles. The original concept of approximate scaling and the concept of scale-breaking were determined in new energy regions, and illustrate the importance of measuring over large kinematic ranges. The idea that the constituents were indeed the quarks of the strong interactions was the first step in the development of a theory which embraces properties of the strong, electromagnetic and weak interactions, i.e. quantum chromodynamics. The aim of this talk is to indicate the various stages in this development as given by deep inelastic charged lepton scattering.

Some physicists believe that higher energies will always reveal exciting new phenomena. Others believe that the high-energy frontier is ending, the masses of the top quark and of the Higgs boson being the only remaining surprises. Practically all else is predicted or predictable from known data. Which view is closer to the truth will be decided by LEP, Europe's planned large electron-positron ring.