Study of the Temperature Dependence of Electron-Ion Recombination in Nitrogen

Abstract

The temperature dependence of the afterglow decay of electrons and ions from microwave discharges in nitrogen-neon gas mixtures has been studied using combined microwave and mass-spectrometric techniques. Under conditions where N2 + is the only significant afterglow ion species, i.e., at nitrogen pressures less than 10~2 Torr, and for neon pressures in the range 15 to 40 Torr, the afterglow is controlled by the recombination of N 2 + ions and electrons. Over the temperature range studied, 205 to 480°K, the recombination coefficients exhibit no significant temperature dependence and can be represented by the constant value a(N2 + ) = (2.7±0.3)X10~7 cm 3 /sec. At any given temperature the results show no systematic dependence on the nitrogen or neon gas pressure over the ranges indicated. Temporal mass analysis indicates similar decay rates for the N2" 1 " ions and for the electrons over the major portion of the afterglow. 194

The role of metastable species in the thermosphere

“…Since the recombination process does not depend on ion temperature, it is clear that they assumed that N2 + was in kinetic thermal equilibrium. Indeed it is probable that they were following a suggestion of Mehr and Biondi [ 1969], who invoked the same dependence in order to account for a difference between their laboratory measurements of the Na + recombination rate coefficient and that of Kasner [1967]. Kasner [1967] heated Table 9a O…”

CRITICAL REVIEW OF N, N + , N + 2 , N ++ , And N ++ 2 MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

“…From an experimental point of view, two classes of studies have been carried out: those measuring directly the rate constant k (Canosa et al 1991;Cunningham & Hobson 1972;Geoghegan et al 1991;Kasner 1967;Mahdavi et al 1971;Mehr & Biondi 1969;Zipf 1980) and those which determined cross sections as a function of the relative energy of the N + 2 ions and electrons (Kella et al 1996;Mul & McGowan 1979;Noren et al 1989;Oddone et al 1997;Peterson et al 1998;Sheehan & St. Maurice 2004). The latter were then able to derive a rate constant by averaging the cross section over a Maxwellian energy distribution.…”

“…They have observed only dissociative charge transfer products with branching ratios (T e /300) −0.39 cm 3 s −1 (±25%). The dissociative recombination of N + 2 has been extensively studied, both experimentally (Canosa et al 1991;Cunningham & Hobson 1972;Geoghegan et al 1991;Kasner 1967;Kella et al 1996;Mahdavi et al 1971;Mehr & Biondi 1969;Mul & McGowan 1979;Noren et al 1989;Oddone et al 1997;Peterson et al 1998;Queffelec et al 1985;Sheehan & St. Maurice 2004;Zipf 1980) and theoretically (Guberman 1991(Guberman , 2003(Guberman , 2012Guberman et al 1993). The interest in the reaction arises because of its involvement in Earth's atmosphere photochemistry (Fox & Dalgarno 1985;Torr & Torr 1979), and more generally in the chemistry of terrestrial planet ionospheres (Fox 1992(Fox , 1993Fox et al 1993).…”

“…Both experiments were in good agreement with each other and led to a temperature dependence of k (T e ) ∼ T −n e (with n = 0.39 or 0.37, respectively). All other rate constant determinations were carried out at T e = 300 K (Canosa et al 1991;Geoghegan et al 1991;Mahdavi et al 1971) or within a reduced temperature range (Kasner 1967). Interestingly, more recent studies from Peterson et al (1998) and Sheehan & St. Maurice (2004) who measured cross sections using merged beam techniques led to the same electron temperature dependence of k (k(T e ) ∼ T −0.39 e ) for T e < 1200 K (Sheehan & St. Maurice 2004), but for a population of ions in several vibrational states among which the ground state accounted for about 50%.…”

Review of rate coefficients of ionic reactions determined from measurements made by the Atmosphere Explorer satellites

“…The laboratory results of Mehr and Biondi [1969], for example, may therefore have yielded apparent dissociative recombination coefficients that cannot be used without reservation in the analysis of ionospheric data. Their results, when they are combined with those of Kasner [1967], are nevertheless in harmony with the AE determination in that both suggest that the recombination rate will increase with vibrational excitation.…”