Using the option -x and -xa the RIXS cross section can be calculated by mcdisp. Option -x calculates resonant inelastic x-ray intensities maximized with respect to azimuth. Option -xa calculates resonant inelastic x-ray intensities with complete azimuth dependence for each reflection.
The formalism is based on [27, equ.8 ff], e.g. the observables are the 9 components ( =xx xy xz yx yy yz zx zy zz) of the tensor , which is related to the operator in  by
Here the vector describes the polarisation of the incoming / outgoing photon beam (linear (real) or circular polarized (complex) light). Vector components (e.g. to the xyz coordinate system, where , and perpendicular to and .
For the isotropic ion the scattering operator is given by
In order to use this expression, the conductivities have to be entered in the sipf file, e.g.
SIGMA0r=1.32 SIGMA1r=1.32 SIGMA2r=1.32 SIGMA0i=1.32 SIGMA1i=1.32 SIGMA2i=1.32('r' and 'i' stand for real and imaginary part, respectively).
Note: in module so1ion the scattering operator is given in terms of the total angular momentum instead of .
If a more complex tensor is required, it's components can be defined in the sipf file using the perlparse option.