Fig. 4: Effect of increasing laser power densities on the K-intermediate counter ion cluster.
The lowest and highest laser power densities are a direct comparison using data collected at SwissFEL (6 ps). The two middle panels were collected at LCLS (10 ps) and SACLA (10 ps), respectively, and are shown for comparison. Difference electron density maps (Fobs(light)-Fobs(dark), negative density in yellow, positive density in blue, contoured at 3 σ) collected at different laser power densities. Each panel includes dark (dark green), light at low laser power (in light green), light (light blue) models, and the damaged structure obtained with the highest laser power density (orange). All models are aligned based on their corresponding dark models. Waters in the dark and light models are marked in purple and pink, respectively. The lower panel shows the refined models and extrapolated density maps (2Fext(light)-Fcalc at 1 σ) for the highest and lowest laser power density collected after femtosecond laser excitation. Retinal SB = retinal Schiff base.
