Relaxation effects in molecularK-shell hotoionization

The effects of core relaxation on the shape-resonant $K$-shell photoionization cross section in ${\mathrm{N}}_2$ are shown to be very significant. Cross relaxation produces substantial broadening and shifting of the shape resonance to higher energy. The results suggest that the frozen-core approximation may not be an appropriate model for $K$-shell photoionization involving a low-energy shape resonance.