Photon W-value for Xe in the soft X-ray region

The W-value for Xe has been measured in the soft X-ray region using monochromatized. synchrotron radiation and a multi-electrode ion chamber. For improving the purity of the incident photons the electron storage ring was operated with an energy lower than the normal mode. The photon W-value was derived on an absolute scale through evaluation of low and high density limits in the gas-density dependence of photoion currents. The W-value changes at the 4p ionization threshold slightly and increases steeply at the 3d threshold. This behavior is compared with the experimental W-value for electrons and that calculated on the basis of a model which takes into account multiple photoionization effects connected with inner-shell ionization. (C) 2001 Elsevier Science B.V. All rights reserved.