NMR LINE-SHAPE IN METALLIC NANOPARTICLES - A MATRIX CONTINUED FRACTIONS EVALUATION

In metallic nanoparticles the different electronic environment seen by each magnetic nucleus produces a distribution of Knight shifts of the NMR frequencies that is observed as an inhomogeneously broadened line shape. We study the fluctuations in the local density of states for s electrons at the Fermi energy in a simple linear combination of atomi c orbitals model. We resort to a matrix continued fractions calculatio n of the Green's functions. Results show that the line broadens asymme trically and its shift decreases as the particle size or the temperatu re diminishes, satisfying a universal scaling function. However, for v ery small particles, surface states become relevant to determine a lin e shape that departs from the universal scaling behavior. These trends are consistent with the tendencies observed in Cu and Pt particles.