Recombination of KrH+ and XeH+ ions with electrons in low temperature plasma

Abstract

Reported is Flowing Afterglow study of recombination of KrH+ and XeH+ ions with electrons at low temperature. In the experiment the plasma was created in a microwave discharge in the upstream part of the flow tube in a fast flow of helium carrier gas at a pressure ∼ 1 600 Pa. Further downstream He-Kr-H2 and He-Ar-Xe-H2 were added to form KrH+ and XeH+ ions, respectively. The electron number density along the flow tube was monitored by an axially movable Langmuir probe. The corresponding recombination rate coefficients were obtained from the rate of plasma decay during the KrH+ (or XeH+) dominated afterglow. The kinetic model was used to optimize dominance of KrH+ and XeH+ ions and to minimize the formation of H+3 ions and fast recombining cluster ions. Since the proton affinity of krypton is only 0.02 eV greater than that of H2, the partial pressures of these reactants have to be adjusted very carefully to obtain plasma with a maximal population of KrH+. Obtained rate coefficients for recombination of KrH+ and XeH+ ions with electrons at 250 K are 2 × 10−8 cm3s−1 and 8 × 10−8 cm3s−1, respectively.