Intensity-dependent control of dissociation pathways in strong-field double ionization of ethylene

Abstract We investigate the dissociation dynamics of ethylene (C 2 H 4 ) in strong femtosecond laser fields using a reaction microscope. Coincidence ion detection enables reconstruction of fragment momenta and identification of multiple two-body channels of C 2 H 4 2 + , including C 2 H 3 + + H + , CH 2 + + CH 2 + , and C 2 H 2 + + H 2 + . Particular attention is given to the symmetric CH 2 + + CH 2 + channel. With increasing laser intensity, the kinetic energy release peak shifts from 5.2 eV to 7.3 eV, indicating a transition from dissociation via lower excited states (e.g., 3 B 3u and 1 A u (S 2 )) to higher-lying states (e.g., 3 Ag and 1 B 3g ). The observed evolution of state populations highlights that peak laser power density governs the selection of dissociation pathways. By tuning laser parameters, specific channels can be enhanced or suppressed, providing an effective approach for steering molecular fragmentation dynamics in polyatomic systems.