Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Light on The "Split Peak" of Alcohols

15.10.2014

New study in the journal "Structural Dynamics" makes sense of mysterious spectra, paving way for RIXS spectroscopy to probe dynamic electronic structure of complex liquids and materials

For scientists probing the electronic structure of materials using a relatively new technique called resonant inelastic soft X-ray scattering (RIXS) in the last few years, a persistent question has been how to account for "split peak" spectra seen in some hydrogen-bonded materials.


S. Schreck, HZB/UP

In this picture the resonant inelastic soft x-ray scattering (RIXS) spectrometer in the foreground and the liquid jet sample delivery system in the background.

In RIXS, low-energy X-rays from synchrotron or X-ray free-electron laser light sources scatter off molecules within the studied material. If those molecules include light elements, such as the -OH group in alcohols, the complex spectra RIXS produces are difficult to interpret. Controversy has surrounded the split peak structures.

The prevailing interpretation has been that spectra revealed some twin aspect of the materials -- a split signal related to two separate structures within the molecules. But now a team of researchers in Germany has performed an investigation of several types of liquid alcohols with RIXS and brought new perspective to this long-lasting debate.

In the journal Structural Dynamics, from AIP Publishing and the American Crystallographic Association (ACA), they show that the split peaks are tied to dynamic motions produced in response to the scattering X-rays themselves -- an observation that helps resolve the intricacies of RIXS spectra, extending the utility of the technique for investigating the molecular structure and dynamics of many complex materials.

“We found that the split peak structure in the RIXS spectra of liquid alcohols originates predominantly from nuclear dynamics during the RIXS process,” said Simon Schreck, a researcher with the Institute for Methods and Instrumentation for Synchrotron Radiation Research at the Helmholtz-Zentrum Berlin and with the University of Potsdam in Germany, who led the research as part of his doctoral work under supervision of Professor Alexander Föhlisch.

“We significantly improved the understanding of RIXS spectra from complex liquid systems, alcohols in particular,” said Schreck. In addition, he said, the approach he and his colleagues worked out “can be readily applied to other systems where nuclear dynamics during the RIXS process have a big influence.”

Split Peaks Revisited

In previous studies of liquid alcohols with RIXS, where the dominant peak was typically split into two sub-peaks, their origins were controversial and either assigned to the presence of two different structural motifs in the liquid -- such as rings and chains, ultrafast nuclear dynamics or the molecular electronic structure.

However, by investigating several straight-chain molecules containing an alcohol group, and by shifting the wavelength of the X-rays they used, Schreck and his colleagues solved the mystery. They were able to compare the spectra produced when dynamic nuclear motions during the X-ray scattering process occur (as is typically the case in RIXS) to situations where these dynamics were minimized. This allowed them to produce "dynamic-suppressed spectra," which approximated the molecule’s unexcited electronic state.

Doing so, they found that the scattering-suppressed spectra did not contain split peaks at all. This suggested that the dual spikes found in normal spectra originates from RIXS-induced nuclear dynamics in the O-H bond instead of from the presence of multiple structural motifs. Distinct structural motifs would leave their own signatures on both spectra.

"We found no evidence that this split peak structure is the signature of two distinct structural motifs (hydrogen bonded rings and chains) in the liquid alcohols, as it has been suggested previously for methanol," Schreck said.

The article, "Dynamics of the OH group and the electronic structure of liquid alcohols," is authored by Simon Schreck, Annette Pietzsch, Kristjan Kunnus, Brian Kennedy, Wilson Quevedo, Piter S. Miedema, Philippe Wernet and Alexander Föhlisch. It appears in the journal Structural Dynamics on October 14, 2014 (DOI: 10.1063/1.4897981). After that date it can be accessed at: http://scitation.aip.org/content/aip/journal/sdy/1/5/10.1063/1.4897981

ABOUT THE JOURNAL

Structural Dynamics is a journal devoted to research on the methods, techniques and understand of time-resolved changes in chemical, biological and condensed matter systems. See: http://sd.aip.org/

Jason Socrates Bardi | newswise

Further reports about: AIP Dynamics X-ray X-ray scattering alcohols electronic structure motifs spectra split structure

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

IceCube experiment finds Earth can block high-energy particles from nuclear reactions

24.11.2017 | Physics and Astronomy

A 'half-hearted' solution to one-sided heart failure

24.11.2017 | Health and Medicine

Heidelberg Researchers Study Unique Underwater Stalactites

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>