It is a long-standing dream of scientists to capture the ultra-fast dynamics
of molecular or chemical reactions in real time and to make a molecular movie.
With free-electron lasers delivering extreme ultraviolet (XUV) light at
unprecedented intensities, in combination with pump-probe schemes, it is now
possible to visualize structural changes on the femtosecond time scale in
photo-excited molecules. In hydrocarbons the absorption of a single photon may
trigger the migration of a hydrogen atom within the molecule. Here, such a
reaction was filmed in acetylene molecules (C2H2) showing a partial migration
of one of the protons along the carbon backbone which is consistent with
dynamics calculations on ab initio potential energy surfaces. Our approach
opens attractive perspectives and potential applications for a large variety of
XUV-induced ultra-fast phenomena in molecules relevant to physics, chemistry,
and biology.Comment: 21 pages, 3 figures, submitte