Optical properties and electron-attenuation lengths from photoelectric-yield measurements*

Abstract

The photoelectric yield of an infinitely thick medium is examined as a function of the polarization and angle of incidence of the incident light, the refractive index, n, and extinction coefficient, k, of the photoemitter, and the attenuation length, L, of the photoexcited electrons in the photoemitter. It is found that the photoelectric yield is a maximum at an angle very close to θc given by n = sinθc and that the magnitude of the yield at this angle, relative to that for normal incidence, is dependent on k and L. In practice, if we know the polarization of the incident light, a least-squares fit of the experimental photoelectric yield as a function of angle of incidence can be made to the theory using n, k, and L as the adjustable parameters. This method is most sensitive for the determination of optical constants when n is close to, but less than, unity and k and L are small. These are just the conditions generally found in the soft x-ray region where it is difficult to obtain accurate optical constants from reflectance measurements. It is suggested that, in the energy region where it is applicable, this method for obtaining optical constants may be easier and more accurate than reflectance methods. When the magnitude of the yield near θc is dependent on both k and L, this quantity may be used to determine L if k is measured independently.