Calculation of x-ray emission spectra of molecules and polymers by the Green's function method

We use the one-particle Green's function for calculations of x-ray spectra of molecules and polymers. The x-ray rates are obtained as the residues of the one-particle Green's function modulated by x-ray orbital transition moments. The latter are optionally decomposed into atomic contributions using local symmetry selection rules in line with the standard intensity model for molecular x-ray emission. Applications are performed for molecules in the sequence ethylene, butadiene, hexatriene, and polyacetylene. Site selectivity leads to surprisingly molecular-like structures in the theoretical polymer spectrum, although the bands are quite broad. The effect can be interpreted from the singularities of the spectral density of the one-particle Green's function.