THE NATURE OF THE VECTORIAL PHOTOELECTRIC EFFECT IN THE THRESHOLD ENERGY REGION

An immediate correlation has been proved to exist between the vectoria l photoelectric effect and electronic surface structure modified due t o adsorption. Experimental studies were performed for Cs overlayers on W(110) and Si(111) faces using visible exciting photons with energies below those of both bulk and surface plasmons. Considerable (more tha n 20 fold) growth of the effect was observed for p-polarized light in the vicinity of threshold as the light frequency approached the positi on of the maximum of local density in the surface-state band. A specia l case of the vectorial photoelectric effect for p-polarized light has been found in the absence of bulk photoemission excited by s-polarize d light. Our results prove that the anomalous vectorial photoelectric effect is caused by the normal electric vector component of the p-pola rized light under appropriate conditions for the particular photoemiss ion enhancement on the surface. The effect can be related to optical a bsorption by the surface-state band and to subsequent electron emissio n into the vacuum, the normal electric vector component of the p-polar ized light being essential for both processes.