Nav: Home

THz spectroscopy could help Explain water's anomalies

June 27, 2018

WASHINGTON, D.C., June 27, 2018 -- Liquid water sustains life on earth, but its physical properties remain mysterious among scientific researchers. Recently, a team of Swiss researchers used existing THz spectroscopy techniques to measure liquid water's hydrogen bonding. Future efforts with this technique could one day help explain water's peculiar properties. The team reports their findings in The Journal of Chemical Physics, from AIP Publishing.

"What makes this paper special is the aspect of THz spectroscopy of a liquid. In the THz range, we make spectroscopy explicitly of the intermolecular degrees of freedom of the system in the study, to contrast it to intramolecular degrees of freedom," said Peter Hamm, an author on the paper. "With THz spectroscopy, we can very directly look at the hydrogen bonding between various water molecules."

Researchers use spectroscopy to measure the interaction of matter with light and infer something's physical composition. In this experiment, the researchers excited a dye molecule dissolved in water with an ultrashort visible laser pulse, changing its charge distribution. Then, a THz pulse measured the response of the surrounding water molecules as a function of the time after that excitation process.

THz spectroscopy, which is relatively low frequency, enables researchers to examine the forces that exist between water molecules. Observing these intermolecular forces could help researchers understand water's anomalies, because hydrogen bonding in liquid water molecules make up many of water's unexpected properties, like its unusual density maximum at 4 degrees Celsius.

"The response we found in the THz frequency range was surprisingly slow. Water is typically considered to be a very fast solvent with a response in the subpicosecond range, but we found a timescale around 10 picoseconds in the THz," Hamm said. They attributed the slow timescale to the collective nature of the water response that was probed using THz spectroscopy.

Hamm clarified that researchers have been using THz spectroscopy for more than 20 years and cautioned optimism about the results. "The outcome often has been a bit disappointing because the THz spectra of liquids like water are extremely broad and blurred, and it's very hard to extract information out of that," he said. Time-resolved techniques, like in this study, might overcome that limitation.

Next, the researchers plan to use their method to look at water's structure and dynamics when it's still liquid, but below the freezing point. Hamm explained, "The special properties of water become significantly more pronounced if one goes to temperatures below the freezing point."
-end-
The article, "Aqueous solvation from the water perspective," is authored by Saima Ahmed, Andrea Pasti, Ricardo J. Fernandez-Teran, Gustavo Ciardi, Andrey Shalit and Peter Hamm. The article appeared in The Journal of Chemical Physics June 19, 2018, (10.1063/1.5034225) and can be accessed at https://aip.scitation.org/doi/10.1063/1.5034225.

ABOUT THE JOURNAL

The Journal of Chemical Physics publishes concise and definitive reports of significant research in the methods and applications of chemical physics. See http://jcp.aip.org.

American Institute of Physics

Related Spectroscopy Articles:

X-ray photoelectron spectroscopy under real ambient pressure conditions
Researchers in the Institute for Molecular Science (Japan) and their collaborators have improved an ambient-pressure photoelectron spectroscopy instrument using hard X-rays and succeeded in photoelectron spectrometry under real atmospheric pressure for the first time in the world.
Researchers create first significant examples of optical crystallography for nanomaterials
Researchers at the University of Illinois at Urbana-Champaign have developed a novel way to determine crystal type based on optics -- by identifying the unique ways in which these crystals absorb light.
Optical spectroscopy improves predictive assessment of kidney function
A new optical spectroscopy technique developed by researchers at Lawrence Livermore National Lab promises to improve accuracy and lower costs of real-time assessment of kidney function, reports an article published this week in the Journal of Biomedical Optics.
Coming to a lab bench near you: Femtosecond X-ray spectroscopy
Berkeley Lab researchers have, for the first time, captured the ephemeral electron movements in a transient state of a chemical reaction using ultrafast, tabletop X-ray spectroscopy.
Light scattering spectroscopy helps doctors identify early pancreatic cancer
Pancreatic cancer has the lowest survival rate among all major cancers, largely because physicians lack diagnostic tools to detect the disease in its early, treatable stages.
Paleolake deposits on Mars might look like sediments in Indonesia
In their GSA Bulletin article published online last week, Timothy A.
NMR spectroscopy platform to target the development of new therapeutic agents
Implementation of a new nuclear magnetic resonance (NMR) spectroscopy platform will provide professors Nicolas Doucet and Steven LaPlante of Centre INRS-Institut Armand-Frappier with a powerful new tool for conducting an ambitious research program aimed at identifying new therapeutic molecules.
Mapping Biodiversity and Conservation Hotspots of the Amazon
Researchers have used remote sensing data to map out the functional diversity of the Peruvian Andes and Amazon basin, a technique that revealed hotspots for conservation.
Mapping biodiversity and conservation hotspots of the Amazon
Researchers have used remote sensing data to map out the functional diversity of the Peruvian Andes and Amazon basin, a technique that revealed hotspots for conservation.
Forthcoming comprehensive reference guide on deep tissue imaging techniques
A forthcoming reference book for new deep tissue imaging techniques, to be published Jan.

Related Spectroscopy Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".