The FEMTOSPEX facility at BESSY II is a unique setup to study ultrafast dynamics with soft X-ray pulses down to ~100 fs pulse duration and variable linear and circular polarization. It was installed in 2004 as the first undulator-based slicing facility worldwide and is still, in 2011, the only place yielding soft X-ray pulses (250-1400 eV) of ~ 100fs duration. In addition it is now linked to tunable wavelength pump lasers for resonant and non-resonant excitation.

The most intriguing feature of FEMTOSPEX certainly is its capability of easily switching between ~100 fs and ~1 ps and ~100 ps time resolution just employing different accelerator settings and modes.