Ultrashort pulsed laser and electron accelerator

Summary

In 2004, a new research project has tarted to extend our time-resolved experimental techniques into the femtosecond time regime.
Excitons and charge carrier can undergo a variety of processes on a (sub)picosecond timescale , which are relevant for the operation of opto-electronic devices. These processes include (non)radiative decay of excitons, exciton dissociation into free charge carriers, exciton-exciton annihilation, charge carrier thermalization and trapping and exciton formation by electron-hole recombination.
The new ultrashort pulsed laser and electron accelerator facility will be used to obtain fundamental insights into ultrafast dynamics excitons and charge carriers. The studies will provide information about the relation between the properties of excitons and charge carriers and the nano- to mesoscopic structure of materials. The knowledge to be obtained can be of use for the improvement of the performance of molecular (opto-)electronic devices.
The facility is based on a femtosecond Ti:S laser system. Optical pump and probe pulses with wavelengths from the UV to the IR can be produced. In additon a set-up for THz conductivity measurements is available.
To avoid the problems associated with the assignment of the species responsible for transmission changes in optical pump-probe experiments, a 5 MeV pulsed picosecond electron accelerator is being constructed. The use of high-energy electron pulses makes it possible to (almost) exclusively produce free charge carriers.
The facility is unique in the sense that charge carriers and excitons can be created by both ultrashort laser and high-energy electron pulses, while their properties and dynamics can be detected by THz conductivity measurements and optical methods.

The project is funded by a VICI proposal granted by NWO (Netherlands Organisation for Scientific Research) Division of Chemical Sciences (CW).