Dependence on the Initial Configuration of Strong Field-Driven Isomerization of C₂H₂ Cations and Anions

We have investigated the femtosecond laser-induced fragmentation of C 2 H 2 q ion beam targets in various initial configurations, including acetylene (linear HCCH), vinylidene (H 2 CC), and cis / trans . The initial configuration is shown to have a tremendous impact on the branching ratio of acetylene-like (CH q 1 + CH q 2 ) and vinylidene-like (C q 1 ′ + CH 2 q 2 ′ ) dissociation of a specific C 2 H 2 q molecular ion. In particular, whereas C 2 H 2 + generated from C 2 H 2, a linear HCCH target, exhibits comparable levels of acetylene-like and vinylidene-like fragmentation, vinylidene or cis / trans configuration ion beams preferably undergo vinylidene-like fragmentation, with an acetylene branching ratio ranging from 13.9% to zero.