Theory of Optical Excitation of Plasmons in Metals

The usual Fresnel theory of reflection and transmission is shown to be incorrect when applied to materials in which longitudinal (electrostatic) polarization waves, such as the bulk plasma wave (plasmon), may propagate. A new macroscopic theory incorporating polarization waves is developed and applied to optical excitation of plasmons in metals. It is shown, that above ${\ensuremath{\omega}}_{p} ({\ensuremath{\omega}}_{p}^{2}=\frac{4\ensuremath{\pi}n{e}^{2}}{m})$ the reflectance of a semi-infinite slab is diminished by plasmon excitation; and the mechanism of the plasma resonance absorption (predicted earlier in thin metal films) is discussed in detail. Numerical results for Na and K are presented along with a discussion of possible experiments.