Photoelectric effect from CsI by polarized soft x-rays

Further studies are reported on the polarization dependence of the photoelectric effect produced by soft X-rays from CsI. A major difficulty in these experiments is the geometrical effects which mimic the polarization signature. We present a detailed calculation of these geometrical effects that are produced when the X-ray beam is not precisely aligned on a rotatable plane photocathode. These effects were observed experimentally and were used in turn to precisely determine the alignment of the incident beam of polarized X-rays on a rotatable photocathode. From these studies, were are able to uniquely determine the true polarization dependence of the photoemission from CsI. We confirm that the photoelectric effect in CsI is dependent on the polarization state of the X-rays. The 'phase shift' which was reported previously has now been explained as a result of these off-axis effects. This shows that there is no intrinsic 'phase shift' in the polarization dependence of the photoemission from CsI. Preliminary surface analysis of the CsI photocathode was performed to determine the surface quality.