Table of contents

The applicability of the concept developed by Kalinkin and Shmonin is discussed using experimental data on π-¹²C interactions at P_π- = 40GeV/c.

A good agreement with the model is obtained for all experimental data considered: multiplicity distribution of charged particles, rapidity distribution, average transverse momenta, partial inelasticity coefficients, etc.

Closed expressions for the radial integrals appearing in DWBA for first order excitations have been derived. It is found that for weakly absorbed particles these integrals are very sensitive not only to the elastic scattering phase-shifts, as predicted by the Austern-Blair theory, but also to the relative phases of the Bessel functions.

Lifetimes and relative intensities of the C₂ (d-a) Swan bands have been remeasured using the High Frequency Deflection technique, yielding τ(d, ν = 0-6) = 120 ± 4 ns. With increasing pressure of the C₂H₂ target gas strong second lifetime components occur revealing collisional transfers from other C₂ levels with rate coefficients around 6 × 10^-11 cm³ s^-1 mol^-1. These transfers are also observed with a number of other catalyser gases such as He, Ne, Ar, N₂, and CO₂. The transfer processes explain the considerably longer lifetimes reported in several earlier life-time investigations and could be a clue to the formation mechanism of the carbon high pressure bands.

For the Na-like Zn XX ion energy levels and transition arrays 3s-np, 3p-ns, nd, 3d-np, nf, 4s-np, 4p-ns, nd, 4d-np, nf, 5s-np, 5p-6s, nd, 5d-6p, nf, 6p-nd, 6d-nf and 7d-7f are calculated by the Dirac-Hartree-Fock method for n ⩽ 7. Theoretical wavelengths are compared with experimental values for transitions observed so far. Theoretical and experimental values agree to within 0.30% for most cases.

The triplet spectrum of doubly excited Be III has been studied in the wavelength region of 75-5000 Å in order to test the validity of the theoretical term values reported by Lipsky et al. The beam-foil excitation technique was applied to effectively populate the doubly excited states. The identified lower-lying, doubly excited states 2p²³P, 2pnp³P, or ³D, and 2pnd³P, or ³D (n = 3, 4) show that the theoretical term values should be slightly modified.

New spectrographic observations have been made of the flashes of light appearing in small burning iron particles produced in a grinding wheel. In a dispersion of about 80 Ångström per mm slitless spectra of individual flashes show a great number of Fe I lines as well as molecular bands due to FeO, C₂, CN and N₂. The region observed is between 5160 and 5870 Å. These observations confirm earlier observations by the writer, that discharge phenomena appear in connection with the splitting of a particle in two or more parts. That is to say, the light emission of a flash is due to a discharge spectrum superimposed on a continuous spectrum due to thermal emission.

Possible astrophysical applications are briefly discussed.

The electron motion at cyclotron resonance in the presence of a homogeneous time dependent magnetic field and a standing h.f. electric field is studied in the relativistic approximation. It is shown that the relativistic mass of the electron "follows" an increasing magnetic field in such a way that the ECR condition is fulfilled during a long time, independently of the initial phase and velocity, if the growth of the magnetic field is not too sharp. The results of the approximate theory are confirmed by numerical computations from the exact relativistic equation of motion. Possibilities of using this effect for ion accelerating up to 10 MeV energy range, producing powerful pulses of γ-ray bremstrahlung and strong synchroton emission sources are indicated.

Exact Vlasov equilibria of plasmas with locally Maxwellian velocity distribution are studied. It is shown that the distribution function must be of the general rigid-rotor type, combining both rotation and translation, and the whole system has helical symmetry. The equilibrium equation for these systems is derived. The well-known rigid-rotor equilibria of θ- and z-pinches are obtained as special cases. The equilibrium for the linear screw-pinch is solved numerically; a two-parameter family of self-contained equilibria is obtained. The meaning of the Maxwellian velocity distribution is discussed within the context of collisional evolution of plasmas.

The linearized coupled-mode equations for parametric instability are solved exactly for various cases. The exact evolution of a localized wave-pulse in an unbounded interaction region is used to illustrate the relationship between damping rates, group velocities and instability. Criteria for absolute and convective instability follows in a natural way. The pulse-evolution in a finite interaction region is presented. It is shown that the boundaries create "kinks" in the pulse-profile travelling back and forth at the group velocities, and that the over-all effect of finiteness is to reduce the instability growth. The instability development from a time-constant point source, turned on at a given time, is studied. We find that in the case of parallel group velocities, the solution is stationary behind a front moving with the slowest group velocity. When the group velocities are anti-parallel, and the criterion for convective instability is satisfied, the amplitudes grow asymptotically towards a stationary solution which is explicitly given. Finally, it is demonstrated that a mismatch in frequency or wave number will produce frequency and wave number shifts, but does not otherwise change the growth of the instability.

The dispersion relation is derived and analyzed for a magnetized electron plasma in the field of a powerful circularly polarized homogeneous pump wave propogating along the constant magnetic field. It is shown that decay instabilities appear for a weak pump while a strong pump, in which the electrons reach ultrarelativistic velocities, leads to aperiodic instabilities.

This paper considers the anomalous growth of the radiation intensity, which is caused by an EM wave incident on an inhomogeneous non-stationary plasma. The amplitude of the reflected signal can thus during relatively short time intervals be larger than that of the incident wave. The reason is that the plasma parameters can pass through values, for which linear resonance of leaking surface waves exist. An analytical expression is obtained for the maximum value of the intensity of the reflected wave for two different plasma density profiles, interacting with waves of different polarization. It is shown that the effect can occur repeatedly in a nonstationary plasma with a nonmonotonous density profile, if the region, where the inhomogeneity gradient changes sign, increases.

A non-ideal surface is defined as one which does not reflect specularly the quasiparticles (e.g., charge carriers or excitons) reaching it from the inside. This is described in terms of a phenomenological reflection parameter p and an empirical phenomenological theory is developed on this basis. The meaning of p is discussed in terms of energy conservation (for dielectrics), charge conservation (for metals) and the physical picture of the phenomenological model of surface scattering embodied in it. The problem, amounting to finding the EM field near the surface, is solved as a function of p, for arbitrary values of p permitted by conservation principles. In particular it is shown how to construct a model of a rough (even totally diffuse) dielectric surface without violating energy conservation. The theory is tested with numerical applications for both, metals and dielectrics.

We have derived general formulas for the induced density of states (DOS) for an adsorbate on a metal and have, in particular, specialized to the limiting cases for which the adsorbate potential is weak and strong. We have shown that the energy dependence of the unperturbed local metal DOS influences strongly the induced DOS. This leads to a correlation between the effective potential of the clean metal and the adsorbate resonance position. Such a correlation has earlier been observed in first-principles calculations for adsorbates on simple metal surfaces and certain impurity levels. To illustrate these aspects, we have performed calculations for interstitial and substitutional impurities and for sodium adsorbed on aluminium.

Mössbauer spectroscopy and X-ray investigations show that taenite (f.c.c. iron-nickel alloy) in meteorites generally has decomposed into an ordered phase FeNi with the L10 structure and a disordered f.c.c. iron-nickel alloy containing less than 25% of Ni. The two phases have the same bravais lattice, i.e., they form a pseudo monocrystal. The decomposition is discussed in terms of Fe-Ni phase diagram.

The electron structure of hexagonal GaN has been investigated by means of ESCA. In particular the valence region has been studied. Comparisons with existing pseudopotential band structures are made. The value of an ionicity parameter for GaN is derived from the electron spectrum.

Three different experimental methods of neutron scattering have been employed in order to study the hydration problem in various forms of oriented DNA fibrils. It is found that the water of hydration forms an internal structure in the samples and that this structure is not very strongly coupled to the macromolecular surface. The existence of hydrogen bonds between water molecules is clearly demonstrated. Qualitative agreement between calculated structure factors and measured "elastic" diffraction patterns for a dry DNA sample is obtained. In order to reproduce the measured diffraction pattern for a wet sample it is not enough to include only the water molecules within the first hydration shell in a structure factor calculation. It is concluded that by employing the high resolution "elastic" diffraction technique it should be possible to obtain detailed information on the problem of hydration in DNA.

It is suggested that the passage of a nerve impulse might depend on a local phase change in the annular lipid surrounding the channel proteins in the nerve cell membrane. Several protein distributions and configurations are discussed which have cation transmission characteristics that could be dependent on the state of the surrounding lipid. The threshold voltage depolarization, required to trigger these ionic channels, is considered, and it is concluded that this could occur through dipolefield coupling at the heads of the phospholipid molecules.