The mobility of potassium ions in helium

Abstract

The mobility of ions in helium has been measured at 76.8 K and E/N values up to 15 Td, and at room temperature up to 300 Td. The experimental scatter is of the order of 0.1 - 0.2%. The experimental mobilities are compared with values calculated from a new and accurate ab initio potential (Røeggen et al 1996). The agreement between experimental and theoretical values is significantly better than in earlier studies of this ion - atom system, but some unexplained discrepancies of the order of 1% still exist.

Spectroscopy of K+⋅Rg and transport coefficients of K+ in Rg (Rg=He–Rn)

“…The modified EFG potential given in Ref. 28 leads to values of D e ϭ185.5 cm Ϫ1 , and R e ϭ2.83 Å-both in very good agreement with the values obtained herein.…”

“…We conclude that, on the basis of the spectroscopic constants, there is little difference between the mobilitymodified potential of Ref. 28, and the best potential obtained herein-we shall compare these potentials further when considering the calculated transport constants below.…”

“…the conclusion that the binding energy was not in error by more than 0.4%. In a follow-up paper, 28 that potential was modified in order to fit mobility measurements better. It was concluded that, over the range of the potential tested by the mobility measurements, unexplained discrepancies of ϳ1% still existed between experiment and theory.…”

“…Finally, Skullerud, Løvaas, and Tsurugida 29 constructed a model potential with adjustable parameters, based on well-known analytic forms 23 of the short and long-range regions of M ϩ •Rg potentials; by fitting to the previous ab initio values of Ref. 28. The most accurate potential of these has been concluded 29 to be the modified version of the EGF potential.…”

“…The most accurate potential of these has been concluded 29 to be the modified version of the EGF potential. 28 We calculated potential energy curves over a wide range of R for the three sets of basis sets: aVQZ, aV5Z, and d-aV5Z. From these curves, we calculated rovibrational energy levels, and used these to extract spectroscopic constants.…”