Bremsstrahlung von Elektronen im Feld neutraler Atome
The process of deceleration of electrons by the field of neutral atoms is investigated by the aid of a model approximating the neutral atom by a constant potentialU in the interior of a sphere of radiusγ. The free-free emission coefficient is determined in the general case for an isothermal plasma; in the special case of an impenetrable sphere it is compared with the emission coefficient of the ion bremsstrahlung as obtained by the “soft” approximation. The results show that electron-atom radiation may not be neglegible as compared with electron-ion radiation, and this fact may be used to explain the experimentally observed increase of the emission coefficient with pressure which is more rapid than linear. This is verified numerically in the limiting case of an impenetrable sphere.In addition the bound-free absorption coefficient is determined both in general and in the special case of the H− ion; a comparison is made with the absorption coefficient as obtained byChandrasekhar. By the aid of the method of “best approximation” given in the concluding part of the present paper the quantitiesU andγ may be determined for any neutral atom.