Photon W-value for Ar in the sub-keV X-ray region

Abstract

Absolute measurements of the W-value for Ar have been performed using monochromatized synchrotron soft X-rays and a multiple-electrode ion chamber. For improving the purity of soft X-rays, the electron storage ring was operated with an energy lower than the normal mode and thin filters were utilized. Using the absolute intensity of the soft X-ray beam provided with the ion chamber technique, the photon W-value was derived, which shows a considerable variation with the photon energy near the Ar 2p electron ionization edge. The experimental W-value has been reproduced using a model proposed here, which considers multiple photoionization effects related to inner-shell ionization.