The observation of crucial first femtoseconds in a photochemical reaction requires experimental techniques that are not found in the typical arsenal of femtosecond chemistry. But such fast dynamics can now be studied with the tools of attosecond research. In the study by Galbraith et al., Published this week in Nature Communications, researchers at MBI have studied one of the fastest internal conversion processes in a molecule at all.
When Horst Köppel published his first scientific article on the ionic benzene molecule in 1987, Martin Galbraith was just born. Köppel, professor in Heidelberg, had found the perfect touchstone for the forthcoming development of a new theoretical method, the so-called time-resolved multiple configuration Hartree calculation, for which he and his colleagues became famous during the following decades. The omnipresent benzene molecule in our environment, whose backbone consists of a ring of six carbon atoms, turned out to be the perfect compromise between complexity and chemical relevance. Therefore, the theoretical specialists from Heidelberg have studied this molecule more and more closely and over the years have written more than 30 highly cited publications, while they have developed their technique to a cutting-edge tool of theoretical chemistry, which is now used by scientists around the world.
But one crucial thing was not yet achievable: the confirmation of the theoretical results by a time-resolved experiment. The predicted dynamics were just too fast, on a time scale of about 10 femtoseconds. This extremely small time interval is obtained by dividing a second by 1014, that is, by a 14-digit number.
When Horst Köppel published his first scientific article on the ionic benzene molecule in 1987, Martin Galbraith was just born. Köppel, professor in Heidelberg, had found the perfect touchstone for the forthcoming development of a new theoretical method, the so-called time-resolved multiple-configuration Hartree calculation, for which he and his colleagues became famous during the following decades. The omnipresent benzene molecule in our environment, whose backbone consists of a ring of six carbon atoms, turns out to be the perfect compromise between complexity and chemical relevance. Therefore, the theoretical specialists from Heidelberg have studied this technique, and they have developed their technique to a cutting-edge tool of theoretical chemistry, which is now used by scientists around the world.
But one thing is not achievable: the confirmation of the results by a time-resolved experiment. The predicted dynamics were just too fast, on a time scale of about 10 femtoseconds. This is a very small time interval by 1014, that is, by a 14-digit number.
The present scientific study results from a collaboration of the MBI researchers with the theory groups of Professor Horst Köppel and Alexander Kuleff at the University of Heidelberg. "I think it's great that after so many years that our calculations on benzene ion were just a standard for theorists, a detailed comparison of theory and experiment is now possible and can confirm our calculations," says Horst Köppel. The published work includes recent, more detailed calculations, which Simona Scheit were executed by the Heidelberg group, and shows a very good agreement between experiment and theory.
Molecular dynamics at conical overlaps plays a central role in many key fields of modern chemistry. Often the first femtoseconds are of crucial importance, which until now could not be understood experimentally. That's why Dr. Jochen Mikosch confident about the future of the experimental technique that has now been developed, concludes: "By observing one of the fastest internal conversion processes in a molecule, we have opened a new field that gives us ways to control electronic dynamics in complex molecules. ".
