ESR AND CESR OBSERVED IN ULTRAFINE MG PARTICLES

Electron spin resonance (ESR) of ultrafine Mg particles prepared in ultrahigh vacuum condition are measured. An asymmetrical ESR line (linewidth: 16 G) which has ever been ascribed to the quantum size effect (QSE), is assigned to the O-2 ion adsorbed on the particle surface. Another ESR spectrum with the linewidth of 1 G is also observed with the sample prepared under leaking O2 gas. Quantum narrowing of the ESR linewidth is not perceivable even for the particles having 3 nm diameter. Instead, a very broad conduction ESR line is observed, the intensity of which indicates a typical QSE. The reason for the absence of quantum narrowing is discussed in relation to the shape effect on the energy level statistics. © 1990.