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

More articles from Physics and Astronomy:

nachricht Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun
18.04.2019 | University of Warwick

nachricht In vivo super-resolution photoacoustic computed tomography by localization of single dyed droplets
18.04.2019 | Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

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: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>