Coincidence Electron Spectroscopy for Chemical Analysis /UE52

The Coincidence ESCA instrument is installed at the UE52 undulator, featuring a plane-grating monochromator which delivers soft X-ray radiation with variable polarization. The beamline offers photons in linear polarisation from 110-1900 eV and in elliptical polarisation from 110-1390 eV and can be switched in “one-click” between multi-bunch and the quasi single bunch PPRE mode (PPRE: pulse-picking by resonant excitation).

CoESCA is equipped with two Angle-Resolved Time-Of-Flight spectrometers to measure the 3D angular resolved electron distributions, either independently or in coincidence mode. Shot-to-shot data saving for each of the spectrometers allows for investigating the time evolution of the data and post-processing on slow time scales from minutes to hours. The ArTOFs’ high information rate makes studies of radiation sensitive samples at very low photon flux feasible even in a reasonable acquisition time.

Selected Applications:

• Electronic structure of solids with one-hole (XPS, ARPES) and two-hole (APECS) final state spectroscopies
• Structural information of surfaces and adsorbates with photoelectron diffraction
• Enhanced surface sensitivity and spectral filtering possibilities in coincidence mode

CoESCA end-station layout

Methods

XMCD, LEED, XPD, ARPES, XPS, XPD, Mass Spectrometry, NEXAFS

Remote access

depends on experiment - please discuss with Instrument Scientist

The CoESCA station is equipped with two ArTOF2-EW (SCIENTA OMICRON) spectrometers, with a wide angular acceptance up to 60° (full cone). Further they can be operated either independently or in coincidence mode.  The data is saved shot-to-shot for both spectrometers and hence the time evolution of the data can be investigated in post-processing on slow time scales from minutes to hours. The ArTOFs’ high information rate makes studies of radiation sensitive samples at very low photon flux feasible even in a reasonable acquisition time.

The main experimental chamber features a 5-axis sample manipulator, with the possibility to cool or heat the sample (T = 30-1200 K), put up a bias voltage and measure the sample current for basic absorption measurements. The end-station is equipped with sample loading, storing and preparation facilities. The preparation chamber is equipped with a sample heating stage (up to 800°C), a quartz balance, a mass spectrometer and free ports for mounting user provided equipment (e.g. evaporators). Furthermore, the transfer system is ready for additional, user-provided preparation chambers.