Forces between Excited Alkali Atoms and Noble Gases

Abstract

Positions of satellite bands near the atomic lines of alkali metals in the presence of heavy noble gases together with the assumption of a Lennard-Jones (6-12) interaction potential and knowledge of the attractive force constant $C_6$ are used to determine the repulsive force constant $C_{12}$ for excited states of the alkali atoms. The formula commonly used for $C_6$ is modified and leads to an improved agreement of the calculated values for this constant with experimental measurements. The constant $C_{12}$, derived from satellite-band measurements, is found to rapidly increase with excitation of the alkali atom and to be nearly independent of the noblegas. The values of $C_{12}$ found for 82 excited states of Li, Na, K, Rb, and Cs in the presence of Kr and Xe are represented by a simple power law in the effective principal quantum number of the excited state. The expression appears to have general utility when one atom is a noble gas and the other has one or two excited electrons.