Recent advances in theoretical attosecond chemistry

Abstract

In 2001, the first attosecond pulses were generated. Their application to molecules gave birth to the field of “attosecond chemistry” or in short “attochemistry”. The emergence of attosecond measurement tools has opened up the possibility to observe and control electrons in molecules, on their intrinsic timescale. Because of the time-energy uncertainty principle, attosecond or sub-femtosecond pulses have a large spectral bandwidth and can excite coherently several electronic states, i.e. electronic wavepackets. The latter are non-stationary and undergo pure electron dynamics called charge migration. Challenges faced in the application of theoretical methods to electron and coupled nuclear dynamics in molecules using attosecond technology has stimulated the development of novel computational approaches. In this Chapter, we report recent theoretical works investigating the application of attosecond science to polyatomic molecules. In particular, we discuss the photoionisation dynamics, the electron dynamics of electronic wavepackets notably the induced symmetry breaking, the electronic decoherence caused by nuclear motion but also the search for long-lived electronic coherence and electronic recoherence, the experimental observations of electron dynamics, and finally the charge-directed-reactivity, i.e. the nuclear dynamics induced by electronic wavepackets.

Simulating Attochemistry: Which Dynamics Method to Use?

“…One of the goals of attochemistry is to manipulate the outcome of photochemical reactions through the initial coherent excitation of electronic wavepackets with specific compositions. 13,14 This concept, also referred to as charge-directed dynamics in the literature, has been explored experimentally and computationally in small systems. 15−20 Using the simplest case of excitation to a coherent superposition of two electronic states, the ensuing nuclear dynamics manifest as two components: an intrastate component combining the two adiabatic gradients and an interstate component along the derivative coupling.…”

“…As a result, an electronic wavepacket can exhibit properties that markedly differ from those of pure states populated individually, potentially resulting in a distinct chemical reactivity. One of the goals of attochemistry is to manipulate the outcome of photochemical reactions through the initial coherent excitation of electronic wavepackets with specific compositions. , This concept, also referred to as charge-directed dynamics in the literature, has been explored experimentally and computationally in small systems. − Using the simplest case of excitation to a coherent superposition of two electronic states, the ensuing nuclear dynamics manifest as two components: an intrastate component combining the two adiabatic gradients and an interstate component along the derivative coupling. Notably, the second contribution, which arises from electronic coherence, gives emergent properties to electronic wavepackets compared to traditional photochemistry …”