Interaction of Electromagnetic Waves of Radio-Frequency in Isothermal Plasmas: Collision Cross Section of Helium Atoms and Ions for Electrons

Abstract

The elements of the theory of interaction of radio-frequency electromagnetic waves in gaseous discharge plasmas are reviewed. The applicability of this phenomenon of wave interaction to the measurement of quantities involved in fundamental processes in such plasmas is considered.A measurement of the "effective" electron-atom collision frequency in helium, found to be 3.12\ifmmode\times\else\texttimes\fi{}${10}^{8}$/sec/mmHg for room temperature electrons (\ensuremath{\sim}300\ifmmode^\circ\else\textdegree\fi{}K), gives a value for the probability of collision for momentum transfer, ${P}_{m}$, of the helium atom equal to 24.0 ${\mathrm{cm}}^{2}$/${\mathrm{cm}}^{3}$ at 0\ifmmode^\circ\else\textdegree\fi{}C and 1 mm Hg.An experimental determination of the "effective" electron-ion collision frequency (for singly charged ions) has also been determined which closely agrees with earlier theoretical predictions. The ratio of the effective cross sections, associated with electron collisions, of ions and helium atoms in the room temperature isothermal plasma is \ensuremath{\sim}3.0\ifmmode\times\else\texttimes\fi{}${10}^{5}$ at an ion density of ${10}^{11}$/${\mathrm{cm}}^{3}$.