Electron paramagnetic resonance and electron spin-echo modulation measurements of sodium and potassium ionic clusters in X and Y zeolites

Abstract

Na³⁺₄, Na⁵⁺₆, K³⁺₄ and K²⁺₃ ionic clusters in X and Y zeolites have been studied by electron paramagnetic resonance and electron spin-echo modulation. Field-swept two-pulse ESE gives a hyperfine pattern that indicates that the electron spin in the K²⁺₃ cluster is not equally distributed over the nuclei in the cluster. ²⁷Al nuclear modulation has been observed for all the cluster species. Semiquantitative simulation of the ²⁷Al nuclear modulation shows that the average number of aluminium nuclei interacting with the electron spin in these ionic clusters is around 9; the isotropic hyperfine coupling is ca. 0.8–1.1 MHz and the average distance between the unpaired electron and the aluminium nuclei is within 0.30–0.36 nm.