Overview of the URSA Instrument at FLASH
The URSA instrument is designed for time-resolved photoelectron and x-ray absorption (yield mode) spectroscopy with molecules/atoms in gas phase, for AMO and gas phase chemical science. Samples are typically excited with an optical laser and then probed by an extreme-ultraviolet or soft x-ray pulse from the FLASH free-electron laser.
The URSA-PQ-vacuum system is based on a customized six-way cross chamber of type DN 250 CF. The design allows a versatile use with different equipment and at different beamlines.
The ports on the spectrometer axis and the top port have dimensions equal to the DN 250 CF ports of the CAMP instrument. Especially, the distance from flange to interaction region equals 260 mm.
The magnetic bottle electron spectrometer with energy resolution of about 1/40 allows for retardation and thus optimal electron energy resolution in a flexible kinetic energy range.
We offer gas needles as sample insertion for gases from bottles, evaporating liquids or highly volatile solids. In addition a capillary over allows for the spectroscopy of solid samples with vapor pressures around 10-4 mbar or more at 150 C.
The instrument design and commissioning is described in:
URSA-PQ: A Mobile and Flexible Pump-Probe Instrument for Gas Phase Samples at the FLASH Free Electron Laser, J. Metje et al. Appl. Sciences 10, 7882 (2020)
https://doi.org/10.3390/app10217882
Time-resolved photoelectron spectroscopy is described in:
Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy, D. Mayer, F. Lever et al., Nature Communications 13, 198 (2022)
https://www.nature.com/articles/s41467-021-27908-y
