Simulating Attochemistry using Time-Dependent Density Functional Theory

At the attosecond time scale, short intense laser pulses can create complicated superposition states that give rise to electronic dynamics faster than nuclear motion. Understanding and measuring these processes is a major ongoing emphasis of ultrafast science, but many questions remain concerning the properties of a molecule that give rise to these dynamics, and how they can be observed experimentally. In this talk, I will demonstrate how time-dependent density functional theory (TDDFT) can be used to simulate attosecond electron motion, as well as associated time-resolved observables such as inner-shell transient absorption. We use real-time TDDFT with optimally tuned range-separated hybrids, atom-centered basis sets, and emulate the initial state using constrained DFT. Technical details that will be discussed include: the choice and effect of initial state, the intruder problem for inner-shell spectroscopy, and the role of self-interaction and the exchange correlation functional on the dynamics and spectra. Next, results will be presented for attosecond charge migration (CM) in functionalized bromobenzene derivatives, and how chemical functionalization of a molecule can regulate the dynamics in a chemically intuitive way. Our results, suggest that a density-based picture and simple attochemistry principles are fruitful for predicting and interpreting CM. Finally, I will demonstrate how RT-TDDFT can be use to compute attosecond transient absorption spectra for both molecular (aminophenol) and solid-state (silica, diamond) pump probe experiments. These types of simulations are first steps towards reconstructing dynamics from spectra in attosecond experiments.