Shining light on photoprotective molecules with X-ray light sources

Conical intersections are common occurrences in organic molecules.

These ultra-fast radiation-less decay channels appear when electronic states become degenerate and the Born-Oppenheimer approximations breaks down.

While they have been studied intensely with UV/VIS pump-probe spectroscopy,  their energetically broad features require subfemtosecond pulses in the XUV or X-ray regime.

In this project, we want to theoretically investigate new spectroscopic techniques for more detailed measurements of conical intersections.

We namely will investigate three different techniques, entangled X-Ray photon spectroscopy, two-dimensional high-harmonic spectroscopy, and X-ray Raman spectroscopy for unique signatures of conical intersections.

We will simulate time-resolved spectra with the help of time-dependent perturbation theory and ab initio molecular dynamics. The simulations will be paired with investigations into photo-protective molecules as they are used in sunscreens.

It is known that these molecules use conical intersections to disperse the energy of absorbed UV photons into vibrational degrees of freedom. However, it has also been discovered that oxybezone, a commonly used substance, is  toxic to coral reefs.

A better understanding of the conical intersection mediated deactivation mechanism may key for the development of improved photo protectors.

The above-mentioned spectroscopic techniques will be applied to gain more insight  into ultra-fast radiation-less decay mechanism.