Photoelectron emission and surface state of cleaved mica

The current due to photoelectron emission was obtained for cleaved mica in a vacuum (10^-3 torr) by illumination with ultraviolet light. The photoelectron emission increased with increase in the density of surface states due to the modification of the mica surface by treatment with a neutral Ar beam and HCl solutions. It is suggested that the electrons filling the deeper states were cumulatively excited to the upper states, to be finally emitted by illumination of sufficient luminous intensity, and therefore, the increase in the density of surface states means an increase in the probability of the absorption of photons to transfer electrons to the upper states