  The first step to gain optical control over the ultrafast processes initiated
by light in solids is a correct identification of the physical mechanisms at
play. Among them, exciton formation has been identified as a crucial phenomenon
which deeply affects the electro-optical properties of most semiconductors and
insulators of technological interest. While recent experiments based on
attosecond spectroscopy techniques have demonstrated the possibility to observe
the early-stage exciton dynamics, the description of the underlying exciton
properties remains non-trivial. In this work we propose a new method called
extended Ptychographic Iterative engine for eXcitons (ePIX), capable of
reconstructing the main physical properties which determine the evolution of
the quasi-particle with no prior knowledge of the exact relaxation dynamics or
the pump temporal characteristics. By demonstrating its accuracy even when the
exciton dynamics is comparable to the pump pulse duration, ePIX is established
as a powerful approach to widen our knowledge of solid-state physics.
