COLLISION FREQUENCY MEASUREMENTS IN OXYGEN AND HELIUM MAGNETOPLASMA AFTERGLOWS.
ILLINOIS UNIV URBANA GASEOUS ELECTRONICS LAB
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Collision frequency measurements were carried out in helium and oxygen at thermal energies. The helium measurements yield a collision probability of 18.7 at 300K and 1 torr pressure. This corresponds to a cross section for momentum transfer of 5.29 x 10 to the -16th power sq-cm. at 300K. The helium collision frequency f is directly proportional to approximately the first power of the velocity at 300K. The oxygen measurements yield a value of f 4.6 x 10 to the -8th power NO2u where u is the electron energy in electron volts and NO2 is the number density of oxygen molecules. The measurements were carried out by two independent methods. Author