Ionospheric ion‐molecule reaction rates

Abstract

The current status of laboratory measurements of ion‐molecule reactions of ionospheric relevance is reviewed. Rate constants for the atmospheric loss reactions of He+, O+, and N2+ appear to be established to within about a factor of 2 at 300°K. The laboratory rate constants for O+ and N2+ ion loss are compatible with quiet midlatitude E‐ and F‐region requirements. The He+ loss reactions appear to be higher than is compatible with some He+ concentrations observed; however, the laboratory rate constants have been measured by so many investigators that they are unlikely to be seriously in error. In the D region, on the other hand, many of the important reactions are as yet unmeasured. Measurements of the relevant negative ion reactions with neutrals have only recently been started. No in situ atmospheric negative ion composition studies have as yet been carried out to guide the laboratory investigations. Many positive ion reactions of importance in the D region (as well as in sporadic E layers) remain to be measured. Finally, very little information concerning reactions of excited state ions with neutrals has been obtained. This will be important for certain disturbed ionospheric conditions and possibly for a precise analysis of normal ionospheric conditions, when this is merited.

Vertical Drift Velocities of the Ionospheric F-region During the Eclipse of 12 November 1966

“…We therefore conclude, with other authors (Rishbeth, 1961;Ferguson, 1967;vonZahn, 1967) that the laboratory-determined reaction coefficients and mass-spectrometric values of neutral constituents (particularly atomic oxygen) observed by rockets are not compatible.…”

“…The underlined values are those obtained by laboratory experiments or rocket observations. Chemical reaction coefficients in models 2-5 are taken from laboratory measurements which are summarized by Ferguson (1967), while those in model 1 are assumed in accord with Nicolet (1963) to meet the mass-spectrometric observations of neutral constituents by rockets. a1 and a2 have been assumed as 2x10-7300 and 10-7300 cm3 sec-1, respectively, for all models.…”

Use of ionic mobilities for measurements in the lower ionosphere

“…Thus we see that essentially every such collision results in a charge transfer! It Is not the case that these reactions have unusually fast reaction rates; rather, a reaction rate constant of about 10-10 cm 3 /sec is what one expects for exothermic charge transfer reactions (Ferguson, 1967).…”

“…for which the reaction rate has been measured to be k-1.0 (± 0.5) x 10 cm 3 /sec (Ferguson, 1967). For this collision, kc = 5.5 x 1-10 cM 3 /sec.…”

Binary Positive Ion-Negative Ion Mutual Neutralization Reactions.

“…The determination of binary positive ion-negative ion mutual neutralization (recombination) rates at thermal energies has relatively speaking been ignored , presumably because of the difficulty in establishing suitable interactive media in association with satis factory ion density diagnostic techniques . However , loss of ionization in gases 0 which contain electronegative species may ultimately result from ionic recombination , as is expected to be the case in the lower ionosphere (Ferguson , 1967). The earliest studies of this phenomenon were carried out in weakly ionized gases at high pressures ( ' ' 1 atmosphere) and as such are concerned with termolecular ionic recombination.…”