Cyclotron Resonance Studies of Chemi-ionization in the O+C₂H₂ Reaction

Abstract

DURING an investigation into the kinetics of the O+C₂H₂ reaction in a flow system by electron spin resonance (ESR) spectroscopy (unpublished results of J. N. B. and R. S. T.) an intense signal with an effective g value of 2.00 was detected. The following evidence showed that it was the result of cyclotron resonance of free electrons. The signal appeared with a TE₀₁₂ cavity, with electric lines of force perpendicular to the d.c. magnetic field, but not with a cavity operating in the TE₁₀₂ mode. The application of a d.c. potential to tungsten electrodes inserted upstream of the cavity reduced the signal and produced a measurable current but did not affect the ESR signals. The signal was up to 10⁷ times more intense than that of the normal radical electric dipole transition and was characteristically broad and unsymmetrical with a g value of 2.00 (refs. 1 and 2). The signal versus reaction time profile was similar in shape to those reported³ for the system using Langmuir probe and mass spectrometer detection.