The shape and intensity of fluorescence lines is an important diagnostic tool to explore the characteristics of the material along the line of sight from an X-ray source. We present a Monte Carlo simulation of radiative transfer through a neutral gas, including photo absorption, fluorescent line emission, and Compton (down-)scattering. The primary spectrum is emitted by a source which is located either in the center of a spherical cloud or above a semi-infinite slab. In the former case, a pure

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... ransmitted spectrum is obtained while in the later case the reflected component is of interest. We present the dependence of intensity of the Fe K α and K β line and the centroid energy of the Compton shoulder as a function of N H . These calculations will be implemented in a revised version of the absorption model tbabs which includes lines emission and effective Compton down-scattering from the high energy range. This model is appropriate for column densities in excess of 10 24 cm −2 . An INTEGRAL view of the high-energy sky (the first 10 years) -9th INTEGRAL Workshop and celebration of the 10th anniversary of the launch 15-