LZ12745

Electrons and protons working together for a big molecular bang

When a strong laser pulse hits a molecule, one or more electrons might be stripped off - the molecule becomes ionized. In our letter we describe the discovery of a novel highly efficient ionization mechanism in hydrocarbon molecules of various sizes that drives the molecules into unexpectedly high charge states at very moderate laser intensities. Subsequently it leads to the complete molecular decomposition via a two-stage Coulomb explosion that involves the concerted emission of all protons with remarkably high kinetic energies. We explain our observations by a dynamic ionization mechanism in which the motion of electrons and nuclei is strongly coupled that is well known for diatomic molecules. In our experiment we observe for the first time that this dynamic ionization can proceed in parallel at many carbon-hydrogen chemical bonds within a hydrocarbon molecule. We show this unique fragmentation process for hydrocarbon molecules, but such a molecular decomposition should also occur in general classes of polyatomic molecules, as long as the time-scale of the intra-molecular nuclear motion matches the laser pulse duration. Our finding shows experimentalists an efficient route for controlling laser-induced fragmentation of molecules using the pulse duration as a control knob.