IR-Emissionsspektrum eines Argon-Plasmastrahls zwischen 4 und 25 μm

The infrared emission spectrum of an argon plasmajet was investigated in the wavelength range from 4 to 25 microns by means of a Fourier-transform spectrometer. Besides numerous sharp emission lines of argon (FWHH = 1 cm^?1) several broad intensity maxima are observed at 4.636 μm, 7.435 μm and 12.346 μm with a FWHH of 7; 20 and 39 cm^?1.     

Zur Reflexion und Transmission elektromagnetischer Wellen bei senkrechtem Einfall auf ebene Grenzflächen zwischen unterschiedlich absorbierenden Medien

On Reflection and Transmission of Electromagnetic Waves Propagating Perpendicular to Plane Surfaces between Different Absorbing Media Born and Ladenburg already in 1911 pointed out that to describe reflection and transmission of electromagnetic waves through a plane surface between two different absorbing media in addition to the usual Poynting vectors of the running waves the so called “mixed” Poynting vector is necessary to maintain the balance of energy on the boundary plane. The flow of energy connected with this vector always points toward the region of maximal wastage of this energy and is closely related to the spatial modulation of the energy consumption within the partially standing interference pattern between the incoming and the reflected wave. In almost all substances the energy absorption is caused by the electric field whereas practically a direct contribution from the magnetic field can be neglected. But taking account of these magnetic effects we may get a better understanding of the mixed Poynting vector. To that end we add to the second of the Maxwell equations a quantity analogous to the electric current term in the first Maxwell equation. The amplitude of the “mixed” Poynting vector then turns out to depend essentially on the ratio of the energy absorption by the electric and the magnetic field. To confirm this fact we consider a medium, which shows in addition to the usual electric losses also magnetic ones of comparable magnitudes. In such materials the resultant energy consumption is distributed more similar to the spatial distribution of the fieldenergy. As a result the amplitude of the mixed Poynting vector disappears if the percentage of energy absorption by the electric and the magnetic field and their energy densities themselves are made equal to each other.     

Über die Gültigkeit der Fowler-Nordheim-Gleichung bei der Feldemission von Mikrospitzen auf ausgedehnten Metalloberflächen

The validity of the Fowler-Nordheim equation is discussed for field emission from protrusions on extended metal surfaces. With the model of a semi-spheroid on a plane the permeability of the potential barrier is calculated. It is found that the field enhancement factor calculated from the slope of the Fowler-Nordheim plots is then less than its value on the tip of the protrusion. Furthermore, this slope depends on the field, and it is nearly constant only if the height of the protrusion is above a certain limit. For a multitude of emitters the resulting slope of the Fowler-Nordheim plots is calculated. It is found that this slope is determined practically by the site with the highest field enhancement factor. Finally the influence of gas adsorption is discussed. Patch fields caused by inhomogeneous adsorption, and variation of the adsorption state by secondary processes may have a strong influence on the emission. In this case it is impossible to obtain the values of the field enhancement factor and of the emitting surface from the Fowler-Nordheim plots in a simple way.     

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.