The role of positronium decoherence in positron annihilation in matter

► Decoherence time decrease exponentially with the number of e− interacting with Ps. ► Time scale of the decoherence motivates correction in decomposition of PALS spectra. ► We showed the way of modification for formulas used for PALS spectra decomposition. ► The superposited Ps should contribute to the positronium in matter evolution theory. ► We examined the magnetisation influence to be expected on the process of decoherence.