PHOTON SCIENCE

Exploring the temporal landscapes of complex chemical and biochemical reactions

Time-scales of chemical reactions:
In a chemical reaction, simple or complex, typical time scales of atomic or molecular motions start from femtoseconds, meaning the billionth of a billionth of a billionth of a second. Life relevant motions, however, like moving a pen during writing, can be as slow as seconds or even down to minutes’ or hours’ time scales (depending on the ideas one desires to write down ...).

Beyond Polanyi - temporal landscapes:
Are there any connections between these time scales? How do they look like? To what extend structural motifs “freeze in” in time and dynamics information of chemical reactions? X-rays study structures. Which type of X-ray apparatus needs to be built and which kind of X-ray methods needs to be developed for investigating the created femtosecond “time stamps” in the structure of complex matter during the time course of a chemical or biochemical reaction?

"Molecular movies":
Some time ago, in a proof of principle experiment, it has been postulated that high flux, pulsed X-rays (created with synchrotrons or free-electron lasers) can be used to "film molecular movies” of chemical reactions: after the initiation of a reaction with an ultrashort optical pulse, the proceeding reaction’s structural changes are "imaged" by collecting a series of ultrafast snap shots of X-ray images as a function of time. It has been envisioned that utilizing X-ray photons will allow for the development of methods well beyond energy resolution, temporal resolution and spatial resolution of alternative methods developed so far.

From concepts to chemical rationals:
Till now we have studied about 300 chemical reactions of different types (uni- / bimolecular, non-catalytic / catalytic, cooperative). Since the time-resolved X-ray spectroscopy resp. diffraction experiments allow for detangling local from global/bulk structural responses, desired functionalities of a device can be precisely tuned.

Thus, it has become possible to optimize functional performances i.e. of organic materials or devices with solar cell activities or water-splitting devices utilizing time-resolved X-ray methods.