Quasi-static line profile for the Ca ii K resonance line (dashed, red), compared with the impact approximation (continuous, black). Parameters are 6000 K for the temperature and a neutral He perturber density of 10¹⁹cm^-3. The central region is enlarged in the top panel. The quasi-static calculation is only useful for the wing; approximately within the central region between the crossing points of the two profiles the impact calculation is the superior approximation.