The dedicated QEXAFS facility at the SLS: Performance and Scientific Opportunities

Abstract

The SuperXAS beamline at the Swiss Light Source (SLS) features a permanently installed monochromator for quick scanning EXAFS (QEXAFS) spectroscopy in series with a conventional double crystal monochromator (DCM). All installed optical components like collimating and focussing mirrors can be used by both devices. The remote exchange of the monochromators is possible in less than five minutes while maintaining the beam geometry on the sample. The QEXAFS system allows fast absorption scans down to the millisecond range for the investigation of time dependent processes. Using a Si(111) channel cut crystal the energy range from 5-16 keV can be covered, with a Si(311) cut the range 9.5-30 keV. Usually a quick scanning interval of 0.1° -2° in Bragg angle is selected, thus covering XANES, full EXAFS or multiple edge scans of e.g. all L-edges of a heavy element. Up to about 80 spectra per second can be collected, corresponding to a time resolution of 12.5 ms. The high intensity of the beamline even facilitates fluorescence measurements on dilute samples.

Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

“…A reactor with a larger inner diameter (ID = 1.5 mm) was used for time-resolved measurements in contrast to conventional XAS experiments (ID = 1 mm), to improve the transmission signal. XAS and QEXAFS (quick-scanning extended X-ray absorption fine structure) [80,81] measurements were performed at the Pt L 3 -edge (11,564 eV) using a Si(1 1 1) double-crystal monochromator and a Si(1 1 1) channel cut monochromator (beam size of 200 lm  200 lm; about 1/100 of the length of the catalyst bed) at the Super XAS beamline [82] at SLS (Villigen, Switzerland). The linear absorption coefficient was measured in transmission mode using ionization chambers developed for quick data readout at 2 Hz [83].…”

Spectroscopic Techniques

“…An example is shown in Figure 6.22 of the dynamics of redox reactions of ruthenium in alternating oxygen and hydrogen ambient atmospheres, investigated at the SuperXAS beamline of the Swiss Light Source [21].…”

Scientific Opportunities for Heterogeneous Catalysis Research at the SuperXAS and SNBL Beam Lines

“…Therefore, the development of time-resolved methods and multi-technique approaches providing complimentary information is critical for the advance of catalytic science. [1,3,10,11] In this article, we review the stateof-the-art research tools available at synchrotrons for catalytic science based on experiments performed at the SNBL and SuperXAS beam lines. These two facilities share a common purpose and they provide the users with highly complementary techniques.…”