Fig. 3: Amplification of structural motion requires the pump–dump delay to be within the vibrational dephasing time, not the excited-state lifetime.
From: Optical control of ultrafast structural dynamics in a fluorescent protein
a,b, Vibrational-coherence transfer dominates the observed displacements on a femtosecond timescale for the PDP condition (a). A test for Tannor–Rice coherent dynamics moved the dump delay to 2 ps (b), after vibrational dephasing but well within the 50-ps excited-state lifetime. c,d, A comparison of the PDP experiment with a 350-fs dump time (c) conducted at SACLA reproduces the LCLS experiment in Fig. 2 in detail. Fo–Fo difference maps are shown at 3σ level and 1.5 Å resolution. Strong decay of the difference signals is observed when dumping at 2 ps after dephasing, as predicted by Tannor–Rice coherent control (b,d). A schematic representation of coherence in the ground state (S0) and excited state (S1) is shown in the Wigner phase-space representation as the evolution of momentum p and position q of the S0 and S1 wave packets (a,b). A full coherence simulation using a density-matrix calculation including Wigner transforms is presented in Fig. 4, Extended Data Fig. 8 and Supplementary Section 13.
