Fig. 2. Pump-probe Cu K-edge X-ray absorption of [Cu₄(PCP)₃]⁺.

a Experimental Cu K-edge transient X-ray absorption difference spectrum corresponding to the transition to the triplet excited state of [Cu₄(PCP)₃]⁺ (1 µs time window after the photoexcitation) (black line with error bars (standard error of mean)), experimental ground state spectrum (blue line), theoretical ground state spectra corresponding to P-coordinated Cu atoms (black line) and C-coordinated Cu atoms (red line). b Kinetics measured using transient XAS for the incident beam energy 8.980 keV (red line) and exponential fit of these data (black line).