Application of XFEL to the measurement of x-ray flux irradiating bio-molecules by using x-ray emission from hollow atoms produced from multiple x-ray absorption

We propose the measurement of x-ray flux irradiating bio-molecules by the theoretical treatment of atomic processes together with multiple x-ray absorption. This measurement is useful for the application of x-ray free electron lasers to the measurement of diffraction patterns of bio-molecules, which is indispensable for the study of their three-dimensional structure. The charge numbers of atoms such as C, N, O in bio-molecules, which appear in the fluorescent x-ray spectroscopy from singly inner-shell ionized atoms and hollow atoms, may inform us of the x-ray flux. Furthermore, it is found that the ratio of the number of fluorescent x-ray photons from the hollow atoms to that from the singly inner-shell ionized atoms is in proportion to the x-ray flux irradiating these atoms. This ratio may also be used for the measurement of the x-ray flux.