Chemical processes initiated by light are extremely widespread and their applications cover vital research fields such as medicine, computing and energy conversion.

However, photochemical reactions are limited by the nature and finite number of excited electronic states of molecules and therefore often lack control and selectivity.

To overcome this fundamental limitation, ATTOP proposes to bring recent technological advances in attosecond science to photochemistry and to explore the emerging field of "atto-photochemistry". Indeed, light pulses of attosecond duration have a large spectral width and excite several excited electronic states simultaneously and coherently. This superposition, called "electronic wavepacket", has a new electronic distribution and should therefore lead to a new chemical reactivity. The following question remains unanswered for the moment: What is the reactivity of a molecule in these new types of experimentally accessible electronic states?

The emerging field of atto-photochemistry requires significant theoretical support from the outset. With a unique combination of expertise in both attoscience and theoretical photochemistry, the ATTOP team aims to accurately describe chemical reactions induced by electron wavepackets via attosecond pulses. The ultimate goal is to develop a general know-how to design electron wavepackets and attosecond experiments transforming the result of photochemical reactions for various applications.