Electron–ion recombination rate constants for some compounds of moderate complexity

Abstract

Electron–ion recombination has been studied for the systems N2, CH4, C3H8, neopentane, NH3, and CO2 by use of a microwave conductivity method coupled with pulse radiolysis. Rate constants were determined by analysis of the directly observed electron disappearance. All data pertain to 297 °K. Corrections were made for competing electron losses by extrapolation to zero of a plot of apparent second-order rate constant versus reciprocal of initial electron concentration. No attempt was made to try to identify the positive ions present. The rate constants for the first four compounds showed little change with pressure over the range 1–100 torr with the value found at 100 torr about 20%–50% higher than that at 1 torr. Values for pressures of 10–50 torr are 2.5×10−6 for N2, 3.9×10−6 for CH4, 5.8×10−6 for C3H8, and 4.2×10−6 for neopentane (all cm3 molecule−1 ⋅sec−1). The values found for NH3 varied from 4.6×10−6 at 1 torr to 11.2×10−6 at 10 torr. Data for CO2 were less reliable but showed a change of from 4×10−6 at 1.5 torr to 11×10−6 at 100 torr.

The ionospheres of the major planets

“…The parent gas serves to identify the recombining plasma. For CH4 a plasma recombination rate of 3.9 x 10 -6 cm 3 s -I has been measured by Maier and Fessenden [1975] at room temperature, somewhat larger than the Rebbert et al [1973] value of 1.9 x 10 -6. The dominant recombining ions are probably CH5 + and C2H5 +.…”

“…The dominant recombining ions are probably CH5 + and C2H5 +. As the complexity of the heavy hydrocarbon ions increases, the recombination rate increases initially (e.g., 5.8 x 10 -6 cm 3 s -I for C3H8), but eventually it decreases with greater complexity (e.g., 4.2 x 10 -6 cm 3 s -I for neopentane [Maier and Fessenden, 1975]). Although it is not obviously applicable to our discussion, it is interesting to note that recombination for an NH3 plasma is pressure dependent with a rate varying from 4.6 x 10 -6 at 1 torr to 11.2 x 10 -6 cm 3 s -I at 10 torrs [Maier and Fessenden, 1975].…”

Dissociative recombination study of N3+: Cross section and branching fraction measurements

“…18,19 Due to the relatively high pressures, N 4 + was assumed to be the most dominant ion and its recombination with electrons dominated the electron loss. 18,19 Due to the relatively high pressures, N 4 + was assumed to be the most dominant ion and its recombination with electrons dominated the electron loss.…”

“…10 The linear C ϱv structure was verified experimentally in 1982. 18 In 1972 Sauer and Mulac obtained a rate constant of ͑3.0± 0.6͒ ϫ 10 −6 cm 3 s −1 for pressures of 280-980 Torr. 12 The situation became increasingly ambiguous when a subsequent theoretical calculation again predicted the C ϱv geometry of the X 3 ⌺ − state with r 12 = 1.43 Å and r 12 = 1.2 Å.…”