Dispersive X-ray Absorption Near Edge Structure

Dispersive XANES

The new monochromators at 25-ID allow for switching optics to sets of multilayers, which provide a polychromatic beam with a 3% bandwidth, increasing the X-ray flux by 10 to 100 times that of the Si(111) monochromator.

In this dispersive setup, KB mirrors are used to focus the incident beam to approximately 1 um, and a sample is placed at this focal point.

The transmitted X-rays through the sample are analyzed by a convexly bent silicon crystal called a polychromator. The variation in Bragg angles along the crystal's surface results in the dispersion of the polychromatic beam. Then through the use of an area detector, different X-ray energies can be resolved in a single shot. As a single-shot technique, DAXS offers significant advantages for XAS mapping and time-resolved measurements.

Initial spectra measured on standard references samples replicate those from a standard double crystal monochromator (DCM).

Future plans include implementation of fly scanning of the sample stage to achieve rapid 2D XANES mapping capabilities, particularly for in-situ and in operando measurements.

Variation in concentration through edge step analysis

Variation in oxidation state through edge position analysis