Ultrafast relaxation processes in ethylene cation investigated by sub-15-fs extreme-ultraviolet pulses

The capability to follow the ultrafast internal relaxation dynamics which take place in molecules few femtoseconds after light excitation is of paramount importance to study the photostability and photochemistry of relevant molecular systems [1,2]. The high number of internal degrees of freedom which may play an active role makes the study of these dynamics a true challenge also in relatively small prototype molecules like ethylene. The existence of many different relaxation non-adiabatic paths leading to the same final observable can prohibit a clear experimental observation and makes difficult the theoretical modelling.