The increasing availability of short timescale spectroscopy techniques allows for more accurate probing of nuclear and electronic dynamics. This work studies the underlying potential energy curves for the core-ionized and core-excited states of ClF. The variational collapse that can occur using conventional variational methods make electronic states involving core-holes particularly challenging to describe. Coupled-cluster methods can avoid such problems. This work applies extensions of ground and excited state coupled-cluster methods to compute potential curves for core-hole states of ClF. The ability to obtain accurate potential curves for such elusive states, and generate core-absorption spectra, opens the door for exciting developments. (C) 2017 Elsevier B.V. All rights reserved.