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 Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

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: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>