Reducing Radiation Damage in Soft Matter with Femtosecond Timed Single-Electron Packets

We study the effects on radiation damage of using a femtosecond laser-driven, pulsed electron source in an otherwise conventional transmission electron microscope. We demonstrate precise control - at the single electron level - over the emission timing and the number of electrons emitted with each femtosecond laser pulse. We find that radiation damage is significantly reduced for such pulsed beams when compared to conventional ultralow-dose methods for the same dose rate and the same total dose. We also show that the degree of damage can be controlled by carefully varying the time between arrival of each electron at the specimen and by changing the number of electrons in each packet.