Innovative Station for In Situ Spectroscopy
Obviously, the understanding of the interaction of a catalyst surface with the reactants plays a key role in a detailed description of catalytic processes. X-ray photoelectron spectroscopy (XPS) is a well-established powerful tool to study in detail the outermost surface of solids but it was traditionally restricted to high vacuum and low pressure conditions. However, recently a methodology based on a differentially pumped electrostatic lens system has gained much interest.
The Fritz-Haber-Institut der MPG has operated at BESSY such an instrument since 2002 at different undulator based beamlines. In 2007 a beamline (ISISS) dedicated to near ambient pressure XPS (NAP-XPS) experiments has been implemented at HZB/BESSY II. A further improved version of this instrument is installed as the ISISS beamline since June 2013. A picture of the set-up can be seen as Fig. 1 while Fig. 2 shows a sketch of the main components.
Fig. 2: Scheme of the NAP-HE-XPS endstation installed at the ISISS beamline.
The spectrometer (right site) is displayed retracted from the XPS cell module (left side).
Table 1: Gas analytics
Table 2: Laboratory facilities at ISISS
|Monochromator||ISISS plane grating monochromator|
|Experiment in vacuum||yes|
|Temperature range||room temperature up to 1000 K|
|Detector||2D delay line detector (2D DLD) (SURFACE CONCEPT, Mainz)|
|Manipulators||various, optimised for sample environment|
|maximum pressure||2000 Pa|
|minumum pressure||10-10 Pa|
|typical pressure||100 Pa|
- X-ray photoelectron spectroscopy (XPS) under high vacuum (p=10-10 Pa) and near ambient pressure conditions (typically p=100 Pa).
- X-ray aborption spectroscopy (XAS) at pressure up to 1k Pa with NAP-HE-XPS endstation. Installation of variable pressure XAS endstation instead of NAP-HE-XPS allows NEXAFS in electron yield mode at variable pressure between 1 - 100 kPa at temperatures up to 650K.