Surface-Plasmon Excitation in Small Spherical Graphite Particles by X Rays

Abstract

X-ray scattering experiments have been carried out on dried colloidal graphite, for scattering angles $\varphi =0\mathrm{}°$ and $\varphi =10\mathrm{}°$, using $\mathrm{Cr}K{\beta }_1$ line as a primary radiation. The spectrum for $\varphi =0\mathrm{}°$ shows a faint new component shifted by 13±1 eV from the primary line; the same line was also found for a scattering angle $\varphi =10\mathrm{}°$. If the dried colloidal graphite was replaced by dried colloidal graphite embedded in gelatine, the new component moved to a position shifted by 10 ± 1 eV from the primary line. The corresponding experiments with polycrystalline graphite did not show such components. These new components can be attributed to a plasmon excitation on the spherical surface of each particle of colloidal graphite. This experiment shows that surface plasmons can be excited in small spherical particles independently of the scattering angle.