Figure 6.

Experimental and calculated Fe K-edge XANES spectra of (molecular) [Fe(terpy)₂]²⁺. With the experimental data, both detection modes (TFY: thick lines and HERFD: dotted lines) are presented; for the theoretical spectrum (thin line), only the electric dipole contribution is plotted. (a) LS ground state; the theoretical spectrum was calculated using the ¹A₁ structure. (b) Partially excited [Fe(terpy)₂]²⁺ (Laser ON, Δt = 80 ps); the theoretical spectrum was constructed as a linear combination of the calculated LS (60%) and HS (40%) spectra. (Given the similarity of the two theoretical HS spectra, the reconstruction was done only for the ⁵E structure for clarity.) (c) Photoinduced HS state of [Fe(terpy)₂]²⁺; the plot shows the experimental spectra reconstructed from the laser ON and LS measurements (utilizing the population from XES) and the theoretical spectra calculated for both possible HS states, ⁵E (thin line) and ⁵B₂ (dashed line). (d) Transient XANES obtained as the difference of the laser ON–LS (ground state) spectra.