Figure 4
Synchrotron-based time-resolved experiment. (a) Sketch of the experimental set-up showing the fixed timing t of laser and X-ray pulses and the pump–probe delay τ. If the optical excitation pulse arrives earlier at the sample than the gated section of the X-ray probe pulse, the pump–probe delay τ is positive. The probe pulse is divided into three sections: leading edge (1), ultrafast gate (2) and trailing edge (3). (b) Measured (black dots) and simulated (green dash-dotted, black solid, blue dashed and red dotted lines) pump–probe correlation signal Xc. The error bars indicate a confidence interval of ±32%. The simulations were obtained using equation (1) . The angle is color-coded. All simulations are for the fluence F = 15 mJ cm−2 used in the experiment. Only the red dotted curve is simulated for an optimized fluence of 20 mJ cm−2. (c) Shortened X-ray probe pulses for different incident angles on the PicoSwitch color-coded as in (b). The black dashed line is the original X-ray probe pulse. (d) Simulated initial (C0) and (e) final ( ) contrast as defined in Fig. 1 for different Bragg angles on the PicoSwitch. The black solid lines show simulations for a pump fluence of 15 mJ cm−2. The red dotted lines show a contrast for stronger excitation with a fluence of 20 mJ cm−2. The colored vertical arrows mark the angles where the probe pulses in (b) and (c) were calculated. The gray shaded area marks the angular resolution of the PXS measurement. |