Fig. 2: Release of axial CO from photoexcited Fe(CO)5 synchronous with the symmetric stretch mode in axial Fe–C bonds.

a Schematic diagram for definition and relevance of the R12(ax) coordinate in axial CO dissociation, and the angular difference (Θ = Θ1 − Θ2). b Plot of distribution of R12(ax) as a function of time for the 94 trajectories yielding axial CO release. c Rate of axial CO release as a function of time (obtained from the dissociation times τdissoc) showing clearly visible periodic bursts ~90 fs apart. The rate curve is obtained by applying a smoothing Gaussian convolution of the distribution of τdissoc with a full-width half-maximum of 10 fs. d, e Two-dimensional cuts in the potential energy surfaces (PES) of S6 (top) and S3 (bottom) states obtained by time-dependent density functional theory (TDDFT) scans along the axial Fe–C R1(ax) vs R2(ax) distances. The white scatter overlaid on the PES shows segments populating these states in the trajectories in (b).