Laboratory rate coefficients for positive ion-neutral reactions in the ionosphere

Following the initial suggestion by Bates and Massey [1947], the significance of ion-neutral reactions in controlling the abundance of ions in the earth's ionosphere has been widely discussed in a number of theoretical papers [Bates, 1955; Bates and Nicolet, 1961; Norton et al, 1963; Nicolet and Sunder, 1963; Dalgarno, 1964; Ferguson et al., 1965a, Donahue, 1966]. Further indications for the predominant effects of ionic reactions have been provided by actual measurements of ion density profiles with rocket-borne mass spectrometers [Johnson, 1961; Taylor and Brinton, 1961; Holmes et al., 1965]. However, until recently, the relative importance of many reactions in the ionosphere could not be assessed because a detailed knowledge of the individual thermal rate coefficients was either lacking or rather uncertain as a review of Paulson [1964] demonstrated. Since then, efforts in several laboratories have resulted in the experimental determination of many of the required rate constant values.