Ultrafast dynamics in acetylene clocked in a femtosecond XUV stopwatch.

Few-photon induced ultrafast dynamics in acetylene (C₂H₂) leading to several dissociation channels--deprotonation (H⁺+C₂H⁺ and H⁺+C₂H²⁺), symmetric break-up (CH⁺+CH⁺) and isomerization (C⁺+CH₂⁺)--were investigated employing the (XUV; extreme ultra-violet)-pump-(XUV; extreme ultra-violet)-probe scheme at the free-electron laser in Hamburg, combined with multi-hit coincidence detection. The kinetic energy releases and fragment-ion momentum distributions for various decay channels are presented. The C⁺+CH₂⁺ and H⁺+C₂H²⁺ channels reveal clear signatures of ultrafast molecular mechanisms, demonstrating potential applications of our pump-probe technique to complex systems in order to study a large variety of ultrafast phenomena in the XUV regime. [ABSTRACT FROM AUTHOR]