Fig. 2: Two-color HHS scheme for probing molecular charge migration in N₂ and CO₂.

a, b Measured harmonic signals of H22 and H27 in the two-color experiment of N₂. Measurements at different relative phases of the two-color lasers provide sufficient data sets for resolving the multichannel electronic dynamics. c, d Reconstructed population amplitude of the \(\tilde{X}\) state (∣p_X∣) and the relative phase between the wavefunctions of \(\tilde{X}\) and \(\tilde{A}\) states (Δϕ_XA) in N₂ for the alignment angles of 0° (red circles), 30° (black circles), 60° (orange circles), and 90° (blue circles), respectively. Each circle represents the excursion time of a single harmonic order, as depicted in Fig. 1b. e, f Reconstructed population amplitudes of the \(\tilde{A}\) state (∣p_A∣) and \(\tilde{B}\) state (∣p_B∣) in CO₂ for the alignment angles of 0° (red triangles), 45° (black triangles), and 90° (blue triangles), respectively. g, h Reconstructed relative phases between the wavefunctions of \(\tilde{X}\) and \(\tilde{A}\) (Δϕ_XA) and \(\tilde{X}\) and \(\tilde{B}\) (Δϕ_XB) states in CO₂ for the above three angles. Shaded areas in (c–h) represent the standard deviations of the reconstructions. These amplitudes and phases retrieved for each harmonic order are used to construct the wave packet of the hole dynamics of the cations.