Nonadiabatic molecular dynamics simulation of ${\mathrm{C}}_2{\mathrm{H}}_2^{2+}$ in a strong laser field

The calculated relevant energy levels and two possible ionization–dissociation pathways. The lowest line is the ground state of neutral ground state ${}^1{\mathrm{\Sigma }}_{\mathrm{g}}^{+}$. The two green lines are the ground and excited states ²Π_u, ${}^2{\mathrm{\Sigma }}_{\mathrm{g}}^{+}$ of ${\mathrm{C}}_2{\mathrm{H}}_2^{1+}$. The upper six lines are the states of ${\mathrm{C}}_2{\mathrm{H}}_2^{2+}$.

Schematic geometry and initial electron density distribution of the ${\mathrm{C}}_2{\mathrm{H}}_2^{2+}$ molecule.

The temporal profile of the electric field.

Time evolution of chemical band C–H, C–C in (a) parallel and (b) perpendicular orientations.

Force analysis of H₁ [(a) and (b)] and H₂ [(c) and (d)] with parallel [(a) and (c)] and perpendicular orientations [(b) and (d)]. The red line, green dash dot–dot line, blue dash–dot–dash line, and black dash line are the total force, electron force, laser force, and ion force, respectively.

(a) Time evolution of R_CH1 with parallel (blue dash line), perpendicular (red solid line), and the laser-free case (black dash line). (b) The ratio of the ionization yield between parallel and perpendicular orientations.

Slice of the electron density distribution at t = 5.8 fs for (a) perpendicular and (b) parallel orientations.

Time evolution of N–N band length with parallel (red line) and perpendicular (blue dash line) orientations. The laser parameters are the same as those in Fig. 5.