Forthcoming Events

01.10.2020 - 01.10.2020, AkademieHotel, Karlsruhe, Germany
26.10.2020 - 28.10.2020, Paul Scherrer Institut (PSI), Villigen,Switzerland

News

New scientific highlights- by MUST PIs Chergui, Milne and Wörner
New scientific highlights- from MUST researchers at PSI
Promotion to full professorcongratulations to Steve Johnson!
The Laser at 60: Ursula KellerOPN interviewed OSA Fellows
Former EPFL PhD student Edoardo Baldini wins the 2020 ACS PHYS Division Young Investigator Awards
New scientific highlights- by MUST PIs Banerji, Chergui and Wolf
Prix de l'innovation AGROVINA 2020- for Agrolase: detecting spores of pathogens in real time
Ruth Signorell receives the Humboldt Prize- awarded in recognition of outstanding achievements in research and teaching

Toward time-resolved laser T-jump/X-ray probe spectroscopy in aqueous solutions

December 16, 2019

Most chemical reactions, natural or man-made, are driven by thermal effects. This makes their monitoring in “real-time” difficult, and only equilibrium experiments are possible. It so happens that in the case of water (the most important solvent in earth) when using short laser pulses with the appropriate infrared wavelength and intensity, the irradiated volume can be impulsively heated by tens of degrees centigrade in 2 to 3 picoseconds.

This impulsive temperature jump (T-jump) has been exploited to impulsively trigger chemical reactions in aqueous media, which were monitored by spectroscopic methods ranging from the infrared to the ultraviolet. These methods deliver valuable information about the chemical reaction but are not sensitive neither to the elements involved, nor to the structure of the reactants.

These limitations have been overcome by the group of Majed Chergui within the Lausanne Centre for Ultrafast Science (LACUS) using X-ray spectroscopy. In a new paper, Olivero Cannelli and colleagues demonstrate for the first time the use of an X-ray probe in a T-jump experiment to observe structural changes over the course of a chemical reaction.

To demonstrate this, the researchers investigated a model thermally-driven reaction where cobalt ions in an aqueous solution containing chlorine ions, change their coordination from water molecules to chlorine ions, upon a temperature increase. This work is a first step towards the time-resolved investigations of thermally-driven chemical and biochemical reactions using X-ray methods.


Fig. 1. Schematic layout of the investigated chemical reaction. The equilibrium can be tuned with changes in temperature or chloride concentration, causing free chloride ions to gradually replace water molecules. In parallel, structural interconversion occurs from the hexa-octahedral to chloro-tetrahedral configuration. (b) Experimental layout of the laser T-jump/X-ray absorption spectroscopy probe. The sample jet schematically represents the closed loop wire-guided liquid jet employed in the experiment.

“So far, probing the structural evolution of reactions by X-rays has only been possible for light-driven reactions because photochemical triggers are impulsive,” says Chergui. “The T-jump method in aqueous media is another trigger that can now be used. This broadens the range of chemical processes that can be dynamically investigated at sources of X-ray pulses, such as synchrotrons and X-ray free electrons lasers."

See also:

Reference: Cannelli, O., Bacellar, C., Ingle, R.A., Bohinc, R., Kinschel, D., Bauer, B., Ferreira, D.S., Grolimund, D., Mancini, G.F., and Chergui, M. (2019). Toward time-resolved laser T-jump/X-ray probe spectroscopy in aqueous solutions. Struct Dynam 6, 064303. (10.1063/1.5129626)

<<
NCCR MUST Office : ETHZ IQE/ULP-HPT H3 | Auguste-Piccard-Hof 1 | 8093 Zurich | E-Mail | +41 44 633 36 02
The National Centres of Competence in Research (NCCR) are a research instrument of the Swiss National Science Foundation
FNSNF