Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Identifying the ’signatures’ of protons in water

14.07.2005


Free protons from acids associate with 1, 2 or 3 molecules of water and the structures can be identified by unique infrared laser spectrum signatures, according to a report in Science by Yale professor of chemistry Mark A. Johnson and his collaborators at Yale, the University of Pittsburgh and the University of Georgia.


Eigen and Zundel models for proton shared by water molecules



Acids yielding free protons are common in biological and chemical systems and the measurement of pH to determine acidity of an aqueous solution is a simple, standard procedure. However, it has not been as easy to determine where the liberated protons are located and how they interact with water molecules.

The scientists tackled these questions using infra-red laser light, at much lower energies than were previously accessible, to monitor how the vibration profile changes when a proton is associated with two to eleven water molecules.


The researchers first established a spectral signature for the symmetrically hydrated Eigen cation, which has a minimum energy (H3O)+ ion core and three associated "dangling" water molecules. As they successively added or subtracted water molecules and compared the spectral signatures, they mimicked water fluctuations.

"Surprisingly large spectral shifts are driven by small changes in the hydration environment," said Johnson. "Although previous work anticipated a change from Zundel to Eigen structures as you progress from 8 to 9 water molecules, the change in the low energy bands here is dramatic. The profile for the 9-membered cluster is much like bulk water, but then the 10-membered cluster is again simpler."

The study shows that the proton associated with the Eigen cation undergoes vibrations highest in energy because it supports the greatest distribution of charge, that is, over three H atoms. As different numbers of water molecules surround the H3O+ core, the excess charge can become more localized onto two or even one of the H atoms, causing substantial, size-dependent shifts in the spectral signature of the excess proton. This extreme response to breaking symmetry is consistent with Zundel’s model of the excess proton being a highly polarizable species.

"The basic point is that the proton is a moving target, rapidly switching its character from one species to the next according to how many water molecules it is associated with," said Johnson. "Now that the spectral signatures of various local environments in water are known, the big question left is how this all comes together as we continue to grow crystals toward bulk water (ice)."

Janet Rettig Emanuel | EurekAlert!
Further information:
http://www.yale.edu

More articles from Physics and Astronomy:

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>