Total photoabsorption cross-section of Ar in the sub-keV energy region

The absolute photoabsorption cross-section of Ar in the energy region of 50 eV through 1100 eV has been measured to a high precision using a multi-electrode ion chamber and monochromatized synchrotron radiation. In order to improve the spectral purity of monochromatized synchrotron radiation, an electron storage ring was operated at an electron beam energy that was considerably lower than the normal mode. For most photon energies the obtained photoabsorption cross-sections are in close agreement with data previously reported. However, some discrepancies are noted in the L-shell ionization region.