Quantum Size Effects in Solid State - Nuclear Magnetic Resonance of metallic particles

Abstract

This work involves the preparation of small metallic particles (of diameters of 200 Á or less) possessing a nuclear spin, I=1/2, to be used to study quantum size effects (QSE) and surface effects using continuous wave (CW) nuclear magnetic resonance (NMR) techniques. Solvation and pulse methods were used to determine longitudinal relaxation times, T1, for lead and aluminum powders, where absolute values were found to be 0.45±0.09 and 4.85±0.70 for 207Pb and 27Al, respectively. Approximate values for the Knight shift were also determined (0.168 average for 207Pb and 1.24 for 27Al). In contrast to these findings, 109Ag analysis produced values with high degree of uncertainty. Relaxation times are compared between small particle and bulk measurements, and the relaxation mechanisms and parameters are described.

Keywords

• efecto de tamaño cuántico
• NMR
• relajación de spin-red
• saturación
• efectos superficiales
• desplazamiento de Knight
• spin nuclear