Optimal control of energy redistribution in C60 in strong laser fields

Tim Laarmann, Max-Born-Institut Berlin

Optimal control of molecular processes using intense femtosecond (fs) lasers is one of the hot topics in modern laser science [1]. The goal is to manipulate molecular potential energy surfaces by the strong laser field, which forces a molecular system into a specific relaxation pathway. For instance, the possibility of selective bond dissociation and rearrangement in polyatomic molecules was shown recently [2]. This opens the door to a new exciting scientific field in photochemistry, which could even have application in biology or medicine keeping in mind that large molecules mediate fundamental processes in living organism.
The gain of knowledge by such kind of experiments largely depends on a detailed insight into the fundamental processes induced, when laser light is focused on large finite molecules. With their well defined, highly symmetric structure the fullerenes are model systems acting as interfaces between atoms or small molecules and the solid state. The 60 delocalized pi electrons in the C60 fullerene give rise to interesting but complex photo-physical processes due to correlation effects and the strong interaction with the ionic backbone.
In this talk, we present our latest experimental effort using temporally shaped laser pulses. This is a much appraised technique for controlling and possibly analyzing reaction pathways in complex systems. Closed feedback loop optimization allows one to find optimal excitation schemes on potential energy surfaces of very complex systems without prior knowledge of their structure. We have applied this technique to obtain systematic control on fragmentation processes in C60.

[1] A. D. Bandrauk, R. J. Gordon, and Y. Fujimura, Laser Control and Manipulation of Molecules (ACS Symposium Series Vol. 821, Oxford University Press, Oxford, 2002)
[2] R. J. Levis, G. M. Menkir, and H. Rabitz, Science 292, 709 (2001)