  We perform a comprehensive analysis of the bimagnon resonant inelastic x-ray
scattering (RIXS) intensity spectra of the spatially frustrated Jx-Jy-J2
Heisenberg model on a square lattice in both the antiferromagnetic and the
collinear antiferromagnetic phase. We study the model for strong frustration
and significant spatial anisotropy to highlight the key signatures of RIXS
spectrum splitting which may be experimentally discernible. Based on an
interacting spin wave theory study within the ladder approximation
Bethe-Salpeter scheme, we find the appearance of a robust two-peak structure
over a wide range of the transferred momenta in both magnetically ordered
phases. The unfrustrated model has a single-peak structure with a two-peak
splitting originating due to spatial anisotropy and frustrated interactions.
Our predicted two-peak structure from both magnetically ordered regime can be
realized in iron pnictides.
