Streuung elektromagnetischer Oberflächen- und Volumenwellen an rauhen Oberflächen. Teil I. Allgemeine Grundlagen

Scattering of Electromagnetic Surface and Bulk Waves from Rough Surfaces. Part I. General Theory A classical theory of scattering of electromagnetic surface and bulk waves on rough surfaces (dielectrics or conductors) is given. The primary wave creates a surface polarization on the rough boundary presenting the source for the radiation of scattering. These roughness-caused polarization must be considered in the wave equations and in the boundary conditions of the fields, too. General expressions for the spectral power density of surface and bulk scattering waves will be given. The excitation of surface polarization can result from primary waves homogenously or inhomogenously.     

Eine neue Methode zur Bestimmung der Rauhigkeitsautokorrelationsfunktion von optischen Oberflächen

A New Method of Determining the Autocorrelation Function of Polished Optical Surfaces Starting with a general theory of light scattering a measuring procedure for determining the autocorrelation function of surface roughness of well polished substrates is deduced. In this method light intensity scattered into a fixed direction has to be measured in dependence on the dimensions of the scattering area. The results are tested for a glass surface polished by different methods.     

Streuung elektromagnetischer Oberflächen- und Volumenwellen an rauhen Oberflächen. Teil II. Die Streulichtverteilung; Ein- und Auskopplung von Oberflächenwellen

Scattering of Electromagnetic Surface and Bulk Waves from Rough Surfaces. Part II. The Indicatrix of Scattering; the Coupling of Surface and Bulk Waves In this paper, we present the calculation of the spectral power density of light scattered from homogenously isotropic and rough surfaces which are influenced by bulk or surface waves. A classification of all possible scattering cases in dependence on the wave types which arise in the regions z > O and z < O is given. The dependence of scattered light on scattering angles for the different possibilities of polarisation variantes (∥ and ?) will be presented. The relationship between the correlation function of roughness and the efficiency of coupling between bulk and surface modes will be discussed and compared with the results of other authors.     

Messungen des γi-Koeffizienten,der Zündspannung und des normalen Katodenfalls der Glimmentladung an gasbedeckten Mo- und Fe-Oberflächen in Edelgasen

Measurements of the γ_i-coefficient, the ignition voltage and the normal cathode fall of the glow discharge on gas-covered cathode surfaces for the combinations Mo—Ne⁺, Ar⁺, Kr⁺, Xe⁺ and Fe—Ne⁺ are described. H₂, N₂ and O₂ are used for covering the cathodes with a monomolecular adsorption layer. Measurements are carried out with a dynamic method according to VARNEY in the range 30 ? X/p₀ ? 400 V cm^?1 Torr^?1.     

Zur Mikrowellendiagnostik stromstarker Entladungen mit Skineffekt. Teil 1: Feldverteilung,Oberflächenimpedanz und Strahlungstransport

Using the methods of microwave diagnostics in the case of a dense, cylindrical plasma column, a complex surface impedance and a mean noise temperature, due to the real part of this impedance may be obtained instead of electron density, collision-frequency and noise (electron-) temperature in the usual low density case. In this paper these quantities including the scin-effect are calculated for the axial-symmetric plasma mode of an inhomogeneous plasma column. The mean noise temperature is obtained using a new method based on relations between the corresponding wave-equation and the four pole equations. The result is a differential equation similar to the equation of radiation transfer, but without the well known restrictions of this tool (approximation of ray optics, low damping of the wave).     

Zur Bestimmung des D2O-Gehaltes in schwerem Wasser nach der Schwimmer-Methode

For the evaluation of float measurements all individual steps of the calculations are comprised under the expression of “precise float formula”. From this simplified approximations can be deduced. Their errors are estimated under little restraining conditions. The rather simple “difference formula” in the range of high D₂O-concentration together with a density scale for pure D₂O gained by interpolation suffice for most practical purposes. This is proved by numerical comparing with the precise formula.     

Zur Theorie der parametrischen Anregung von elektrostatischen Oberflächenwellen in einer Plasmaschicht

Dispersion relations for electrostatic surface waves in a homogeneous plasma-layer which interacts with an external electric pumping field parallel to the boundaries are derived in the framework of the kinetic theory. The parametrically excited and purely growing instabilities are investigated. Electric threshold fields and growth rates for the instable surface modes are given. It can be shown that the minimum threshold for parametric excitation occurs for those modes which are symmetric about the midplane of the layer.     

Zur Mikrowellendiagnostik stromstarker Entladungen mit Skineffekt. Teil II: Bestimmung der Plasmaparameter eines angeströmten Stickstoffbogens bei Atmosphärendruck

Microwave diagnostics of an inhomogeneous, dense, cylindrical plasma column may be used to determine the complex impedance and a mean noise temperature in the range of strong skin effect (theory see part I). This case is realized if the specific d.c. impedance E/I falls below a critical value, e.g. 20 Ω/cm for ω = 10¹⁰. It is shown, that for any radial conductivity profile the complex impedance is a function of E/I only. A formula is derived for calculating the noise temperature of the column as a weighted mean value due to the local plasma temperature and conductivity. In the case of strong skin effect this mean value equals the electron temperature of plasma regions near the boundary of the conducting diameter. These results in connection with spectroscopical diagnostics are use to determine some plasma parameters of an arc discharge in a streaming nitrogen atmosphere at 760 Torr. The temperature profil was obtained from the intensity of the 3371 Å molecular band and then the conductivity profile was calculated using an energy balance equation. The results show that even in the 10 A-case the arc plasma is not in thermal equilibrium, the difference T_e—T_g being about 1,500 ºK. This large difference is due to the flow of neutral gas streaming downward the discharge chamber. The length of the discharge (1·3 cm) is not sufficient for the neutral atoms to reach their equilibrium temperature.     

Messungen des γi-Koeffizienten an reinen Mo- und Fe-Oberflächen in Edelgasen

Es werden Messungen des γ_i-Koeffizienten an reinen Katodenoberflächen für die Kombinationen Mo—Ne⁺, Ar⁺, Kr⁺, Xe⁺ und Fe—Ne⁺ mitgeteilt, die mit einer von Varney angegebenen dynamischen Methode im Bereich 30 ? X/p₀ ? 400 V Torr^?1 cm^?1 durchgeführt wurden. Es wird gezeigt, daß die mit dieser Methode im Gas gemessenen γ_i-Werte sich aus den Vakuumwerten von Hagstrum ableiten lassen, wenn

• 1 . die Rückstreuung der emittierten Elektronen und
• 1 . die Molekülionenbildung

berücksichtigt werden. Die Nachlieferung von Elektronen durch Photonen (δ/α) und Metastabile (ω/α) wird unter Verwendung von ω/α-Werten aus Zündspannungsmessungen abgeschätzt. Measurements of the γ_i-coefficient on pure cathode surfaces are described for the combinations Mo—Ne⁺, Ar⁺, Kr⁺, Xe⁺ und Fe—Ne⁺ with a dynamic method according to Varney. These measurements were carried out in the range of 30 ? X/p₀ ? 400 V Torr^?1 cm^?1. It is shown that the measured values correspond to these of Hagstrum obtained in vacuum, if

• 1 . backscattering of emitted electrons and
• 1 . formation of molecules

are taken into account. An estimation is made for electron emission coefficients of photens (δ/α) and metastables (?/α) by calculated ω/α-coefficients from measurements of ignition voltage.     

Bestimmung der Atomspinkorrelationszeiten der Fe3+-Ionen in FeNH4(SO4)2·12 H2O mit Hilfe des Mössbauereffektes

The Mössbauer effect studies of⁵⁷Fe in the paramagnetic salt FeNH₄(SO₄)₂·12 H₂O reported byObenshain et al. were extended to higher values of the applied external magnetic fieldH _a. The results are discussed in terms of the theoretical calculations given byWegener. The data can be fitted using a maximum internal fieldH _max=(598±10) kOe and two atomic spin correlation times τ_c=2,4 · 10^?9 sec andτ′ _c=2,1 · 10^?9 sec.τ _c andτ′ _c are independent ofH _a and the temperatureT. It is assumed in the analysis that the distribution w(H) of the internal fields can be described by a continuous function of the Boltzmann factor type with two parameters. These two parameters are determined by the normalization and the macroscopic magnetization.     

Zur Theorie der nichtstationären Resonanzfluoreszenz an bewegten Molekülen. I Räumliche Energiedichte der Fluoreszenzstrahlung

Non-stationary Theory of Resonance Fluorescence for Moving Molecules. I. Spatial Energy Density of the Fluorescence Radiation The time dependence of the spatial energy density of the fluorescence radiation of an ensemble of moving molecules generated by resonance scattering of intense laser pulses is calculated. Particulary the influence of the duration and the intensity of short laser pulses upon the coherent and incoherent part of the fluorescence radiation of a Doppler-broadened gas is studied. The validity of the conception ?inhomogeneous relaxation time”? is discussed. Within the framework of resonance fluorescence scattering the phenomenon of photon echo is treated.     

Bestimmung des inneren Magnetfeldes in V2O3 mit Hilfe der inelastischen Spin-Flip-Streuung von Neutronen

For the first time the internal magnetic field in a solid was determined by measurement of inelastic spin-flip-scattering of slow neutrons using a neutron crystal spectrometer with extremely high energy resolution. A value of (175 ± 15) kOe was obtained in V₂O₃ at a temperature of 105 °K. Using a hyperfine coupling constant deduced by Jones, this value corresponds to an ordered magnetic moment of 1.25 μ _b per vanadium ion.     

Zur Modulation des Wandstromes in der geschichteten positiven Säule der Neon-Glimmentladung

It is shown, that the wall current of the striated positive column in a neon low pressure glow discharge is modulated with the frequency of the moving striations. There is a phase shift between wall currents of electrons and ions (～π/2–3/4π), A mass-spectrometric analysis of the ion currents shows Ne⁺ and Ne₂⁺ ions, both currents are modulated. The modulation factor of the electron and ion current reaches values near 100% and 50%, repectively. The behaviour of the modulated wall currents may by explained by the potential oscillations in the Langmuir sheath near the wall.