Radiofrequency resonance study of alkali metal ionization in a carbon monoxide flame. Part 1.—General design of the radiofrequency system

Abstract

In Part 1 an analysis is given of the radiofrequency resonance technique. This technique is used for investigating alkali metal ionization relaxation in a carbon monoxide flame (see Part 2). The r.f. resonance measurements yield direct information about the densities of the electrical-charge carriers in the flame plasma. These densities are determined as a function of rise-time of the flame gases. In this context the advantages and disadvantages of the method in comparison with probe technique and microwave methods are discussed. However, we would emphasize that it is not necessary to restrict the application of the r.f. resonance method to the analysis of ionization phenomena in flames.

Since we are interested in small differences in electron density we would note that our r.f. resonance method which operates on the h.f. band (3–30 MHz), is more sensitive in the detection of electrons than microwave methods. Under our experimental conditions the minimum detectable electron density (variation) was 0.6 × 10⁸ cm^–3. A linear response of the r.f. system exists only for electron densities < 1 × 10¹⁰ cm^–3. The temporal resolution in our kinetic studies is ca. 1 ms, depending on condenser dimensions as well as flame rise velocity.