Mobilities of thermal cations in argon and xenon gases: temperature and field dependence

Abstract

In argon at n = (2–6) × 1024 molecules/m3, the density-normalized mobility nμ of argon cations at low electric field strengths E/n is constant from 150 to 300 K; at > 300 K nμ increases. The increase was smaller when the "effective" temperature Teff of the ions was increased by applying higher E/n at 300 K. At 630 K, [Formula: see text] whereas in xenon it was 2.7, and in helium 1.0. The difference in behavior is attributed to the main ions being dimers [Formula: see text] in argon and xenon collision-induced dissociation can occur:[Formula: see text]where * indicates excess kinetic energy acquired by acceleration in the electric field. The dissociation energies of [Formula: see text][Formula: see text] and [Formula: see text] are 2.3, 1.3, and 0.7 eV, respectively. Dissociation of [Formula: see text] is negligible because of its large dissociation energy. Dissociation of [Formula: see text] and reformation of [Formula: see text] is equivalent to the inelastic de-excitation of [Formula: see text]