We investigate the interplay between electronic and nuclear relaxation of the core-excited NO3 anion in solid LiNO3 and NaNO3 by means of the high-resolution X-ray absorption and resonant Auger spectroscopy. It is shown how the relative energy distances between the potential energy surfaces of the intermediate and final states can be mapped using the information on the dispersion of individual participator Auger features upon scanning the photon energy across the resonance. The influence of the cation nature (Li+ or Na+) on the potential surfaces is traced and found to be minimal as a consequence of the rather ionic cation-anion interaction. (C) 2002 Published by Elsevier Science B.V.