Research

Our research focusses on the development and the applications of theoretical methods for simulating the dynamics of molecules beyond the Born-Oppenheimer approximation, i.e., when the coupling between electronic and nuclear motion cannot be neglected and leads to the appearance of the so-called nonadiabatic effects. The breakdown of the Born-Oppenheimer approximation is common for photoinduced and electron-transfer processes, e.g. photochemical reactions, photosynthesis, solar cells, retinal isomerization in the primary step of vision, chemiluminescence, or in atmospheric chemistry, and leads to fascinating phenomena. In fact, nonadiabatic effects are ubiquitous as soon as a given chemical process requires more than one electronic state for its description, but their theoretical description remains an important and arduous challenge due to the necessity of revisiting several critical approximations commonly employed in theoretical chemistry.

The main pillars of our scientific research are the development and the application of theoretical methods for studying the dynamics of molecules in their electronically excited states.

Method development

We are currently working on the development of a hierarchy of nonadiabatic methods centered around trajectory-guided techniques, such as full multiple spawning, with a controllable degree of accuracy. We are not only interested in the accuracy of the nuclear dynamics per se, but also in the inclusion of different additional factors contributing to a precise description of the excited-state dynamics, such as external fields, environment, or relativistic effects. Our group also develops the code OpenFMS, an open-source code to perform nonadiabatic dynamics within the framework of multiple spawning.

Another research program in our group is the description of photoexcitation and how the photochemistry of a given molecule depends on the specific characteristics of the light source used to photoexcite it. Our group developed the promoted density approach (PDA) to generate initial conditions incorporating the effect of photoexcitation by a laser pulse. The PDA code is described here.

We also employ the formalism of the Exact Factorization to study the ultrafast funneling processes of photoexcited molecular systems. If you are interested in the Exact Factorization and discovering how it can be used to analyze quantum molecular dynamics, please visit the code section of this website.

Applications of nonadiabatic dynamics

We apply nonadiabatic techniques to the study of transient molecules of first importance for atmospheric chemistry and to study excited-state processes in various functional molecules or photocatalysts, in direct collaboration with experimental groups. Our group also developed an automated workflow, AtmoSpec, to calculate photoabsorption cross-sections of organic molecules using the nuclear ensemble approach.

We also intensively collaborate with spectroscopists to employ a broad panel of theoretical techniques and study real chemical problems, providing a theoretical support for the analysis of complex experimental data coming from time-resolved spectroscopy measurements (e.g., time-resolved photoelectron spectroscopy, time-resolved X-ray scattering, time-resolved MeV ultrafast electron diffraction).