Raw MbCO data detected at 538 nm (2-nm detection bandwidth). There is an obvious principle oscillation with a period of 50 fs clearly visible in the data. (Inset) Cyt c data detected at 523 nm. No vibrational coherences are observed over the same wavelength range spanning the Q band for the protein.

The spectrum of the LPSVD fit to the background-subtracted MbCO data showing strong oscillations at the ring-breathing mode ν₇. (Inset) Fourier transform of the MbCO data.

(a) The IF generated with a 100-cm⁻¹ filtering window (solid line). The results of the sliding window analysis are shown by the square points in the graph for comparison. The y value of each point is the peak frequency of the Fourier transform of a 200-fs full-width half-maximum Gaussian window centered at the time value of the point. (Inset) Decay in the mode amplitude. (b) Fourier transform of the IF when the IF was generated with 100- and 50-cm⁻¹ windows.

Energy channeling in MbCO. (a) A photon breaks the ligand bond. (b) The Fe—CO bond breaks, and the repulsive iron motion couples to the ring-breathing modes, exciting the modes. (Insets) Details of the ν₇ and ν₄ modes (). (c) The displacement of the breathing modes is part of a superposition of modes that enable the iron to move out of plane and the heme to dome (motions are exaggerated). The doming motion is then coupled to lower-frequency skeletal modes and ultimately to mesoscale motions of the E and F helices (protein motions depicted after ref. ). These panels schematically show the reaction-driven modes and cascade to different length scales of motion along the reaction coordinate.