Volume 25, Issue 4

The energy balance is used to derive a partial differential eqution for the heat flux potential in a rotational symmetric arc column of finite length. This equation is combined with a corresponding equation for the electric potential in order to calculate the distributions of temperature and electric potential for an arc discharge in a strong axial magnetic field. Because the coupling of the two equations is very complicated, all investigations have to be made numerically. The influence of mass flow is studied by taking into account drastically simplified distributions of the azimuthal and radial flow velocities.

The radial ion temperature distribution in a 2600 amp hydrogen arc in a 30 kG axial magnetic field was measured spectroscopically with a Fabry-Perot interferometer by evaluating the half width of Doppler broadened carbon lines. As the admixture of methane had to be low, in order to prevent a strong reduction of the temperature on the axis, the intensities of the C III and C IV lines were relatively weak. Consequently an interference filter with narrow transmission band width was used instead of a spectrograph in front of the F.-P.-interferometer. The broadening of the spectral lines, which were used for measurement, was caused mainly by the thermal Doppler effect. The rotation of the plasma and the macroscopical Doppler effect resulting therefrom did not disturb the measurements. The ion temperature, which was found to be 1.4 × 10 5 °K on the axis, was determined from the half width of the profiles of a C III spectral line. Since the discharge was observed side-on, the measured integrated values were reduced to radial profiles by using appropriate inversion formulae.

In a preceding paper a propagation method has been described that allows simultaneous determination of electron concentration and electron collision frequency in a slowly varying plasma - using its complex refractive index. A regular progressive damped wave had been assumed. In this paper the treatment is extended to the case that the original wave is superimposed by a reflected one. The calculations show that for distinct points in the direction of wave propagation the determination of both modulus and argument of the complex refractive index is again possible. The discrete sequence of measuring points does not restrict the local resolution of the method.

Foils of solid hydrogen were irradiated with a giant pulse ruby laser. The formation and ex-pansion of the plasma produced this way was investigated by time-resolved absorption measure-ments, by streak and framing photography, by holographic interferometry and by time-off-flight and charge collection measurements. The measurements yield a fairly complete picture of this process: After the initial breakdown in the solid a plasma is produced at the surface of the foil facing the laser. Owing to the high pressure of the plasma the solid hydrogen is compressed by a shock wave. This allows the layer in which the plasma is produced to penetrate into the interior of the foil with a velocity of 3 × 10 6 cm/sec. Thus under the action of the focused beam foils up to 1 mm thickness are pierced by the light before the end of the pulse. The plasma cloud, ejected towards the laser, contains 4 × 10 16 ions with a mean kinetic energy of 200 eV this corresponding to about half of the absorbed energy. The observations are compared with the well known results obtained in a plane, one-dimensional geometry. If allowance is made for the influence of the focusing of the laser beam on the structure of the shock front, the observations are readily understood.

The existing model of a "collisionless" alkali plasma diode is extended including the case of two incandescent plane electrodes emitting electrons as well as ions with a half-Maxwellian velocity distribution. The potential distributions within the diode space derived from this theory are examined in detail. Physically necessary conditions reduce the well-known ambiguity of solutions to a single one (with uniform plasma potential) at a given set of parameters. Further solutions, cor-responding to spatially oscillatory potential shapes which are consistent with the collisionless theory, disappear if the ion-ion collision probability within the diode plasma exceeds 0.1 per emitter distance. In the experiment the potential distributions are scanned using a new electron beam probing technique. The results agree with theory.

Ions extracted from a plasma often have to pass a space charge existing in front of the container wall. If collisions occur within the sheath, both, the ion composition and the extraction efficiency may heavily be influenced. The parameters of interest are the extension and the field strength of the sheath. A theory is presented by which these quantities can be calculated. The theory holds for a positive space charge, the orifice being biased negativ with respect to the plasma potential. Numerical results are given concerning a weekly ionized nitrogen plasma.

In this work we develop a collision-dominated sheath model which includes the well known macroscopic models as extreme cases. We set up a description of the charge carriers with the help of the velocity distribution. In order to fulfil the microscopic boundary conditions at the wall we split up the velocity distributions into two parts. A basic set of new transport equations arises which differ from the usual equations by a correction term in the momentum transfer equations. Because of this splitting up of the velocity distribution we are able to take into account exactly specular reflection of the electrons at the wall. In a good approximation our results can also be obtained from the usual equations, if a suitably fitted factor is introduced into the electron boundary condition. at the wall.

Expectation values of kinetic and potential energy are calculated for some lower antibonding orbital states of simple diatomic molecules using H 2 + and HeH 2+ as test cases. Common LCAO-MO theory and a scaling procedure are applied which allow an analysis of atomic orbital interactions in terms of RUEDENBERG'S 1 promotion and interference effect at various internuclear distances. Contributions to the total energy at different regions of interatomic separations are discussed in detail. A characteristic increase of the kinetic energy is observed for antibonding linear combinations at distances where chemical bonding occurs.

The high-field rotational Zeeman effect has been observed in several rotational transitions of the (010) vibrational state in OCS and HCN. The magnetic-field splittings are in agreement with a simple first-order energy expression which is derived to hold for the Zeeman energies of rotation-vibrational states of a linear polyatomic molecule showing rotational l-type-doubling. In this way, the presence of intrinsic magnetic moments in the π-vibrational states has been shown experimentally. The g-values along the molecular axis are g ǁ (010) = +0.061 ± 0.002 for OCS and g ǁ (010) =±0.38 ± 0.06 for HCN. No magnetic anisotropics could be detected within the plane perpendicular to the molecular axis. The other parameters measured are g⊥ (010) = -0.0285 ± 0.0006 and (χ ⊥ - χ ǁ ) (010) = (8.0 ±1.0) × 10 -6 erg/G 2 mole for OCS and g ǁ (010) = ∓ 0.100 ±0.001 for HCN which "can be considered an approximate value for the vibrational ground-state. Either the upper or the lower signs hold for the g-values of HCN. The intrinsic g-values, g ǁ (010) , are discussed in terms of nuclear and electronic contributions. A quantity measuring the slip of a rotating nuclear framework within its electronic environment is defined and also discussed.

Thermoelectric power of stabilized zirconia, at different CaO and MgO concentrations within the cubic phase, has been measured. The results show a concentration dependence of the thermoelectric power which is preliminarly discussed. The homogeneous part of the thermoelectric power, moreover, is discussed with the classical approach of irreversible thermodynamics.

Wilson's GF matrix method has been used to evaluate all the seven independent force constants of some XY 6 type ions using Müller's mathematical constraint. Mean amplitudes of vibration and Bastiansen-Morino shrinkages have also been calculated for these ions.

Luminescence has been observed on exposure of γ-irradiated silicagel to various gases and vapours. The emission spectrum has a maximum at 450 nm and is identical with the spectrum of radiothermoluminescence (RTL) under vacuum with a peak at 55 °C. After radiosorption luminescence (RSL) at 20 °C the thermoluminescence at 55 °C is decreased. The effect of RSL shows that sorbed gases can cause recombination of charges trapped in the gel.

The absolute integrated infrared intensities of the C ≡ C- and the ≡ C - H-stretching vibrations of four acetylenes of the type (CH 3 ) 3 X-C≡C-Y (X = C, Si and Y = H, D) are reported. The obtained values are discussed with respect to the eigenvectors of the normal coordinates of these vibrations and with respect to coupling between these two vibrations and also between these and other vibrations of the type A 1 . An attempt is made to involve the experimental values in an assumed (p-d) π -interaction.