Electron–Photon Pulse Correlator Based on Space-Charge Effects in a Metal Pinhole

A new procedure is demonstrated for cross-correlating light and electron pulses in a time-resolved surface diffraction experiment using low-energy electrons: Ultrashort laser pulses produce a space charge that modulates the transmission of the electron pulses across a pinhole. The proposed method is easily implemented into present pump-probe setups and represents a simple means for establishing spatial and temporal overlap of light and electron pulses on the sample. Moreover, the ultrafast space-charge dynamics allow the temporal resolution of the electron pulses to be characterized down to a time scale of less than 20 ps.