Scattering of fast potassium ions by helium, neon, and argon

A new apparatus has been designed and built, and measurements have been made of the effective total cross sections for the scattering of potassium ions with energies between 150 and 2350 eV by room temperature helium, neon, and argon. The repulsive interaction potentials were deduced from the measured cross sections with two different representations of the potential, the inverse power, and the exponential. The results are as follows (energies are in electron volts and distances are in angstroms): K+–HeV(r)=27.0/r6.22,V(r)=2200 exp(−4.56r),1.18 ≤ r ≤ 1.83,K+–NeV(r)=122/r7.64,V(r)=7850 exp(−4.79r),1.42 ≤ r ≤ 2.02,K+–ArV(r)=667/r7.78,V(r)=8900 exp(−3.96r),1.76 ≤ r ≤ 2.47.These results compare very favorably with other experimental potentials reported recently but are in sharp disagreement with some earlier results. They also disagree with reported potentials which were calculated theoretically, except for the case of K+–Ar where the agreement between theory and experiment is remarkably good. The potentials are also compared to those determined from measurements of the scattering of argon by the same three gases, and the effect on the potential of the additional nuclear charge is discussed.