Solution attosecond chemistry

Introduction

X-ray photons carry sufficient energy to interact with molecular core-shell electrons. Accessible for decades in the energy domain, the resulting core-excited states (CES) can now be observed in the time domain using attosecond (10^-18 s) spectroscopy. These states are important as they govern the lineshapes in all x-ray spectroscopies.

Objectives

Here, we propose to first investigate and then manipulate the CES time evolution in solvated biomolecules in order to reveal key chemical information, including:

• Solute-solvent interactions
• Local symmetries
• Chiral fields

Importance of CES Lifetimes

CES lifetimes dictate the emission of secondary electrons active in radiotherapy. By observing the effect of solute-solvent interactions on CES, we will be able to achieve a better understanding of the first molecular mechanisms of radiotherapy.

Probing Bonding Environments

CES are also a subtle probe of the absorbing atom’s bonding environment. CES line splittings are lost in conventional x-ray spectroscopy due to homogeneous broadening. We developed a technique based on the laser manipulation of CES capable of producing lineshapes up to an order of magnitude below the spectroscopy’s lifetime broadening, revealing core-level splitting.

We will employ this approach to observe core-level splitting in:

1. Solvated amino acids
2. Metalloproteins

This new information will be used to reveal the binding geometry of ligands with unprecedented accuracy.

Nonlinear Optics and Chirality

Finally, we will show how one can use nonlinear optics with attosecond pulses to reveal the chirality of the field surrounding sulfur and phosphorus atoms in biological samples. X-ray excitation localizes the point of view on the chiral field to a single atom. This perspective will allow us to examine the chiral landscape near the target atom.

Here, chirality due to a single chiral center will be probed in L-cysteine, while the chirality due to the macromolecular arrangement will be measured in DNA helices.

Conclusion

Our proposal brings attoscience techniques into the investigation field of large solvated systems.