A Model of Metal-Ammonia Solutions, with Reference to Electron Spin Resonance Experiments

Abstract

An explanation is given of the extreme sharpness of the electron spin resonance line in solutions of potassium in liquid ammonia, as reported by Hutchison and Pastor. Motional narrowing of the width associated with dipolar and hyperfine interactions results from the rotation and diffusion of ammonia molecules. The model of metal‐ammonia solutions used in the calculation is shown to be supported by thermal, magnetic, volumetric, and conductivity data. The model pictures the electrons removed from the potassium atoms as located in cavities in the liquid, the cavities having approximately the volume of two to four ammonia molecules. The electrons in the cavities are in equilibrium with respect to the reaction 2e⇆e₂+0.2 ev, where e₂ represents two electrons in a singlet state in one cavity. The electrons in cavities may perhaps be thought of as in molecular orbital states on the protons of the adjacent NH₃ molecules.