Turbo-XAS

Turbo-XAS is an alternative acquisition mode that allows measuring time-resolved X-ray Absorption Spectra in sequential mode using a dispersive configuration.

In this technique, a narrow horizontal slit selects a monochromatic beam out of the wide polychromatic fan delivered by the polychromator. By scanning the slit across the polychromatic fan, the EXAFS spectrum can be measured, although in a sequential manner in contrast to the dispersive mode. The slits are scanned in a continuous manner and the absorption spectrum is recorded using two ion chambers filled with the appropriate gas mixture positioned before and after the focal point, as is the case in traditional scanning XAFS beamlines.

This technique benefits from the basic assets of the dispersive set-up, i.e. the absence of movement of the optics and the small and stable horizontal focal spot, while featuring simultaneous recording of I0 and It. This method has proved useful when measuring samples in which small angle scattering degrades the data quality in dispersive mode. Time resolutions in the sub-second time range are achievable.

Due to the sequential acquisition mode, turbo-XAS can also be used in fluorescence mode, expanding the capabilities of the beamline.

As the slits select a monochromatic beam, the implementation of turbo-XAS also allows for time-resolved EXAFS to be combined in the same experiment with techniques that need a monochromatic beam, such as x-ray diffraction.