The quantum chemistry of attosecond molecular science

With the advent of attosecond light pulses at the beginning of this century, the possibility to perform real-time observations of electron motion in molecules has spurred impressive theoretical developments aimed at providing support and guidance to numerous, but still incipient, experimental efforts devoted to understand chemistry at its ultimate temporal frontier: the attosecond. The first real-time observation of electron dynamics in a relatively large molecule, phenylalanine, was reported in 2014. This would have been difficult without the help of theory, since observations in this emerging field, recently coined attochemistry, are still indirect. While standard Quantum Chemistry methods can describe excited bound-state dynamics, new approaches incorporating scattering theory formalisms are needed to understand the interaction with attosecond pulses. Indeed, due to their short wavelengths, lying in the XUV and X-ray spectral regions, the interaction of such pulses with any molecule inevitably leads to ionization, which requires describing the molecular ionization continuum. Also, because of their short duration (i.e., large bandwidth), ionization is accompanied by the formation of a molecular electronic wave packet (i.e., a coherent superposition of electronic states), which evolves in time and dictates the fate of the molecule at the longer time scales where chemistry shows up. Although much has already been done up to date, current bottlenecks in the field are to account for electron correlations during the ionization process and for the coupled electron and nuclear dynamics that follows. Past and ongoing theoretical efforts are described here along with experimental work towards the solid establishment of attochemistry. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Quantum Chemistry Theoretical and Physical Chemistry > Spectroscopy