Cross-section measurements for electron-H3O+recombination

Publisher Website
Google Scholar
Abstract
Cross sections for electron-H3 O+ recombination have been measured over an electron energy range of 0.060-1.15 eV by using a trapped-ion technique to contain an ion sample at a temperature of ≃ 400 K. The cross section deduced from these measurements can be represented by σ=4.6×10−18E−2.9 cm2 for 0.038<E≤0.110 eV; σ=4.8×10−16E−0.79 cm2 for 0.110<E≤0.420 eV; and σ=7.5×10−17E−2.9 cm2 for E>0.420 eV. Uncertainties are estimated to be at the ± 50% level. Recombination-rate coefficients were calculated from the deduced cross sections, assuming a Maxwellian electron velocity distribution and trial forms for the cross section below 0.038 eV. Assuming the theoretical E−1 behavior for the cross section just above zero energy and comparing with the measured rate coefficient of Leu et al. at 540 K, we can deduce consistent cross sections below 0.038 eV to be σ=6.0×10−15E−1 cm2 for 0<E<0.023 eV, and σ=4.6×10−18E−2.9 cm2 for 0.023<E<0.038 eV. The calculated rate coefficients have temperature dependence Te−0.5 at 50 K and Te−1.43 at 105 K, and values of the coefficient are in good agreement with all direct measurements.