Ultrafast time-resolved photoelectron spectroscopy with tunable deep UV-pulses

Time resolved photoelectron spectroscopy is a versatile tool for the investigation of ultrafast dynamics in optically dark regions of the molecular potential energy surface. We developed a novel pump-probe-setup, which consists of a magnetic bottle spectrometer and two tunable laser pulses with pulse durations better than 30fs. The pump pulse covers a range of 240 - 400 nm due to frequency doubling of a NOPA and is used to excite the molecules. The temporally delayed probe pulse with 200 - 240 nm tunability ionizes the excited molecules and is generated by sum frequency mixing the frequency doubled output of a second NOPA with a part of the fundamental Ti:sapphire laser pulse. This deep-UV probe pulse samples a large range of the electron kinetic energy spectrum up to 3 eV. The tunability allows us to minimize the contribution of electronic excitations by the probe pulse alone. To achieve pulses with a minimum chirp in the interaction zone we are using prism compressors after each NOPA to give the pulse a positive chirp.