Absolute photoabsorption cross-section measurements of simple molecules in the core-level region

Abstract

Absolute inner-shell photoabsorption cross-section measurements were obtained from a variety of simple gas-phase molecules containing low Z elements (C, N, O, F), independent of the effects of stray light, high-order light, and photoabsorption from the various optical elements. The experimental apparatus consists of (1) a compact high-order light suppressor based on the photon energy dependence of the grazing angle reflectivity of various materials which provides an adjustable cut-off energy, and (2) a gas-phase absorption cell which monitors the photon flux before and after the gas cell to yield measurements independent of the absorptions of various optical elements, response functions of the photon detectors used, and variations of the photon flux during the scans.