Fig. 5.

2D-IR spectroscopy of sw-MsCO-V68Y. (a) Time-resolved IR spectrum of sw-Mb¹³CO-V68Y, 5 ps after 540-nm excitation. (b) Time-resolved IR spectrum of the ¹³CO ligand in the primary docking site B, 5 ps after 540-nm excitation. B₂, B₁, and B₀ populations are observed. The square brackets at the bottom indicate the expected ω₁₂ frequencies of the B₂, B₁, and B₀ substates. (c) 2D-IR spectrum of the A states. (d) Cuts through the T2D-IR-EXSY cross-peaks between heme-bound CO (A₁ and A₃) and CO in the docking site (B₂, B₁, and B₀). The IR_pump energies correspond to the respective arrows in c. (e) The same as b for orientation in f. (f) Overlay of the cross-peak cuts shown in d. The solid lines are calculated spectra.