LiXEdrom: Innovative measuring chamber for X-ray study of liquid jets
Close-up of the liquid-jet.
Schematic drawing of the LiXEdrom setup for X-ray
absorption and X-ray emission
spectroscopy on the liquid-jet
Until now, the only way to study liquids by soft X-ray emission spectroscopy (XES) has been through a membrane window. Now, researchers of Helmholtz-Zentrum Berlin have carried out an XES study of a free micro-liquid jet on the synchrotron.
X-rays are the medium of choice for many scientific studies. When you shine them on a sample, they literally shed light on the material’s structure, providing loads of information about it. Unfortunately, this mostly applies to solids only, since the sample has to be in a vacuum for the entire time it is being irradiated with soft X-rays. For liquids, that means you have to remove all the water. In the case of biological samples such as proteins, however, this destroys their natural environment. The solution to this problems has always been to measure liquids through membranes. These membranes keep the evacuated side separate from the non-evacuated side. The trouble is, one can never really be sure whether or not membrane effects are distorting the measurement results.
At Helmholtz-Zentrum Berlin (HZB), Emad Aziz, head of a junior research group, has shown that liquids can be investigated by X-ray emission spectroscopy without using membranes after all. At the synchrotron source BESSY II, the group has built a special setup – the LiXEdrom. It is unique in that the liquid is shot as a jet through the X-ray beam. The jet from the nozzle becomes so thin and, at 80 metres per second, so fast that the vacuum can be maintained without the need of a membrane.
“On our LiXEdrom, we create a vacuum in the liquid chamber of up to 10-6 millibar, and can now perform both absorption and emission measurements, giving us even more precise information about the structure of a material,” says Emad Aziz. It also allows a clear “view” of elements that possess absorption and emission energies similar to the energies of the membrane materials, and would therefore overlap with the membrane in the spectrum when measured. This concerns above all carbon and nitrogen – precisely those elements of interest in biological samples.
In their first measurements, published in Chemical Physics (DOI: 10.1016/JChemPhys.2010.08.023) and selected for the cover, the group demonstrated they can achieve energy resolutions on their LiXEdrom comparable to those of the latest high resolution XES spectrometers. For water, they have proven that results obtained from an earlier setup were not overlapped by disturbing membrane effects. They have also studied the electronic structure of nickel ions, unhampered by a risk of deposits on a membrane wall distorting the results. For many applications such as protein studies, this is a significant step towards obtaining reliable structural information.
Original paper in Chem. Phys., DOI 10.1016/JChemPhys.2010.08.023
„High Resolution X-ray Emission Spectroscopy of Water and Aqueous Ions Using the Micro-Jet Technique”, K.M. Lange et al.
- BESSY II: How intrinsic oxygen shortens the lifespan of solid-state batteriesAlthough solid-state batteries (SSBs) demonstrate high performance and are intrinsically safe, their capacity currently declines rapidly. A team from the TU Wien, Humboldt-University Berlin and HZB has now analysed a TiS₂|Li₃YCl₆ solid-state half-cell in operando at BESSY II using a special sample environment that allows for non-destructive investigation under real operating conditions. Data obtained by combination of soft and hard X-ray photoelectron spectroscopy (XPS and HAXPES) revealed a new degradation mechanism that had not previously been identified in solid-state batteries. They have gained some surprising insights, particularly regarding the harmful role played by intrinsic oxygen. This study provides valuable information for improving design and handling of such batteries.
- Spintronics at BESSY II: Real-time analysis of magnetic bilayer systemsSpintronic devices enable data processing with significantly lower energy consumption. They are based on the interaction between ferromagnetic and antiferromagnetic layers. Now, a team from Freie Universität Berlin, HZB and Uppsala University has succeeded in tracking, for each layer separately, how the magnetic order changes after a short laser pulse has excited the system. They were also able to identify the main cause of the loss of antiferromagnetic order in the oxide layer: the excitation is transported from the hot electrons in the ferromagnetic metal to the spins in the antiferromagnet.
- Environmental Chemistry at BESSY II: Radicals in waterwaysHow do radicals form in aqueous solutions when exposed to UV light? This question is important for health research and environmental protection, for example with regard to the overfertilisation of water bodies by intensive agriculture. A team at BESSY II has now developed a new method of investigating hydroxyl radicals in solution. By using a clever trick, the scientists gained surprising insights into the reaction pathway.