  Parity is a ubiquitous notion in science and serves as a fundamental
principle for describing a physical system. Nanometer-scale metal objects are
predicted to show dramatic differences in physical properties depending on the
electron-number parity. However, the identification of the electron-number
parity effects in real metal nanoparticles has remained elusive because of the
variations in various features of nanoparticles. Here we report the nuclear
magnetic resonance (NMR) detection of the dynamic effect of the electron-number
parity in silver nanoparticles. With theoretical modeling of the NMR relaxation
in silver nanoparticles, the measured nuclear spin-lattice relaxation rate is
found to be proportional to the electron-number-parity-dependent susceptibility
and to the temperature. This observation demonstrates the
electron-number-parity-governed spin dynamics in silver nanoparticles.
