High Pressure XAS

Contact person:Angelika Rosa (arosa@esrf.fr)

Static high-pressure experiments is one of the key activity at ID24-DCM as it offers optimized high-pressure sample environments. ID24-DCM hosts a laser-heated diamond anvil cell system (see paragraph below) and can accommodate the spectrum of high pressure sample environments, including the membrane type LeToullec-DAC, vacuum vessels for the cryogenically cooled or resistively heated DACs, as well the PEP (Table below). Other DAC types such as the symmetric cell, Chervin-type, BX90 or other user models can be easily adapted.Scientific possibilities include (1) high pressure XAS studies approaching the multi-Mbar regime, (2) fast EXAFS measurements at simultaneous extreme high pressure and high-temperature conditions (P > 200 GPa and T > 4000 K), (3) high pressure studies on chemical complex and heterogeneous systems at the submicron scale, and (4) extreme conditions studies at high dilution levels down to ppm levels for XRF (quantification fo concentration variations) and 500 ppm EXAFS in fluorescence mode. 

The laser-heated diamond anvil cell (LH-DAC) XAS setup at ID24-DCM is a unique facility worldwide that allows performing static XANES and EXAFS experiments under simultaneous very high pressures and temperatures (180 GPa, 5000 K). The LHDAC system at ID24-DCM fully exploits the submicron X-ray spot size and quick/continuous scan possibilities at ID24-DCM. XANES and EXAFS data can be acquired during laser-heating down to 1 second per scan, the new DCM ensures the X-ray beam position and size stability across the energy scan. Tow infrared lasers are used for double-sided heating of the sample. The laser beam size can be varied between ~5-50 m.  Simultaneous double-sided temperature measurements can be performed during a XAS acquisitions up to a frequency of 10 Hz (0.15 ms) using Schwarzschild objectives. User friendly temperature visualization together with the XAS scan and temperature fitting programs are available see figure below. The LH-DAC system at ID24-DCM is very versatile and can accommodate together with classical XAS detection systems (ion chambers)  multiple complementary detection systems including XRF (Vortex single element detector plus polycapillary in backscattering geometry), XRD (Pilatus 2M) and XES (von Hamos spectrometer). A PRL or Raman spectrometer for pressure determination up to 90 GPa and sample visualization is also available.

Photograph of the LH-DAC setup at ID24-DCM. Example of a XAS acquisition with synchronized temperature acquisitions on both sides. Note, that the extended XAS acquisition shown in F) was performed at the Fe K-edge with 410 points and an energy stepping of 1 eV, the total duration was 1.23 s. Figure was modified from Rosa et al (2024).

EXAFS signal in high pressure devices is affected by Bragg peaks occurring on single crystal diamonds. As a consequence, the feasibility of such experiments requires the use of nano-crystalline diamond (NPD) anvils. Good quality NPD anvils are for the moment not commercially available, but can be obtained through a scientific collaboration wit the Ehime University and the  PRIUS proposal submission (GRC, Ehime University, Japan).

More detailed information about high pressure opportunities at ID24-DCM is presented in: 

A. D. Rosa et al. “New opportunities for high pressure X-ray absorption spectroscopy at ID24-DCM and BM23 with the Extremely Brilliant Source of the ESRF”. High Pressure Research, 1–29 (2024). https://doi.org/10.1080/08957959.2024.236428