Further observations of vectorial effects in the x-ray photoemission from cesium iodide

Abstract

We present further data on the linear polarization sensitivity of Csl x-ray/UV photocathodes. A radical physical origin-"nonlocal" photoemission-is proposed for the x-ray vectorial effect. Predictions from a uniaxial photocathode model are compared with measurements of (1) relative pulse quantum yields, relative current quantum yields, and electron number distributions for both <i>s</i>- (electric vector perpendicular to the plane of incidence) and <i>p</i>- (E parallel to the plane of incidence) polarized soft x rays in the wavelength range 4.6-125 &angst;; and (2) relative current quantum yields from illumination by partially polarized, broadband UV radiation with a modal wavelength of 1550 &angst;. An origin seated in the polarimeter geometry is also proposed for the off-axis "phase shift" phenomenon reported in previous papers. The impact of these measurements on (1) an understanding of soft x-ray interactions with materials, and (2) the design and sensitivity of the Spectrum X-Gamma photoemission polarimeter is discussed; our future plans for the investigation of photocathode physics are outlined.