RIXS of Ammonium Nitrate using OCEAN

The {\sc ocean} code allows for calculations of near-edge x-ray spectroscopies using a {\it GW}/Bethe-Salpeter equation (BSE) approach. Here we present an extension of the code for calculating resonant inelastic x-ray scattering (RIXS). Recent work has shown that peak-specific broadening of nitrogen K$\alpha$ emission in nitrates is due to a valence-band lifetime that is an order of magnitude shorter than that of the nitrogen 1s hole, an inversion of the usual assumption that valence holes have longer lifetimes than core-level holes. Using the BSE, including {\it GW} corrections to the DFT energies, as implemented in {\sc ocean} we are able to compare calculations of RIXS with measured spectra of the same. By utilizing an approach free from fitting parameters we are able to identify the origins of various broadening effects observed in experiment.