Extrema in transition energies resulting not in satellites but in dips within spectral lines

The paper deals with a frequently encountered situation where the energy difference between the terms involved in a radiative transition, being plotted versus the radiator-perturber separation, shows extrema. The paradigm, based on 30 years of theoretical and experimental studies, is that the extrema in the transition energy result in satellites in spectral line profiles. In this Rapid Communication we show that this paradigm breaks down: the extrema in the transition energy can also result in dips in spectral line profiles. Moreover, we demonstrate that if the extremum in the transition energy is due to the charge exchange, its spectral signature most probably should be a dip rather than a satellite.