Researchers part water: 'Electric prism' separates water's nuclear spin states

September 8, 2014
Researchers have separated the nuclear spin states of water. In para water, the spins (depicted as arrows) of water's two hydrogen nuclei cancel out. They add up in ortho water. The scientists produced an ultracold, supersonic beam of water molecules -- a mixture of para and ortho water -- and sent it through an electric deflector (blue device on the left). The deflector acts as a prism for nuclear spin states, separating para and ortho water molecules in space (right). Credit: Daniel A. Horke, CFEL/DESY

Using an "electric prism", scientists have found a new way of separating water molecules that differ only in their nuclear spin states and, under normal conditions, do not part ways. Since water is such a fundamental molecule in the universe, the recent study may impact a multitude of research areas ranging from biology to astrophysics. The research team from the Center for Free-Electron Laser Science (CFEL) – a collaboration of DESY, the Max Planck Society and Universität Hamburg – reported its results in the journal Angewandte Chemie International Edition.

At first glance, water seems to be a simple molecule in which a single oxygen atom is bound to two . However, it is more complex when taking into account hydrogen's – a property reminiscent of a rotation of its nucleus about its own axis. The spin of a single hydrogen can assume two different orientations, symbolized as up and down. Thus, the spins of water's two hydrogen atoms can either add up, called ortho water, or cancel out, called para water. Ortho and para states are also said to be symmetric and antisymmetric, respectively.

Fundamental symmetry rules prohibit para water from turning into ortho water and vice versa – at least theoretically. "If you had a magic bottle with isolated para and ortho molecules, they would remain in their at all times," says DESY scientist Jochen Küpper who led the recent study. "In principle, they are different molecular species, different types of water." However, in the real world, are not isolated and frequently collide with other molecules or surfaces in their vicinity, causing nuclear spin orientations to change. "Through these interactions, para and ortho water can actually transform easily into one another," explains Küpper who is also a professor at the University of Hamburg and a member of the Hamburg Centre for Ultrafast Imaging (CUI). "Therefore, it is very challenging to separate them and produce water that is not a mixture of both."

Yet, the CFEL researchers have now demonstrated a way of isolating para and ortho water in the lab. To start, the scientists placed a drop of water in a compartment, which they pressurized with neon or argon gas. This mixture was released into vacuum through a pulsed valve. "Due to the large pressure difference, the gas expands quickly into the vacuum when the valve is opened, dragging along water molecules and, at the same time, cooling them down," says Daniel Horke, the first author of the study.

This expansion produces a narrow beam of ultracold water molecules, which propagate at supersonic speed and are so dilute that individual molecules no longer collide with each other, thereby suppressing the conversion between para and ortho spin states.

The molecular beam then travels through a strong electric field, which deflects the water molecules from their original flight path and acts like a prism for nuclear spin states. "Para and ortho water interact with the electric field differently," Horke explains. "Thus, they also get deflected differently, allowing us to separate them in space and obtain pure para and ortho samples." Spectroscopy showed that the purity of the para and ortho water was 74 per cent and over 97 per cent, respectively. Especially for para water the purity can be greatly enhanced in the future, as Horke says. Storing the separated water species was not an aim of the study.

The new method could benefit studies of a wide range of phenomena. In astrophysics, for example, it is commonly assumed that the relative amounts of para and ortho species can be linked to the temperature of interstellar ice. This theory is based on the temperature dependence of hydrogen's ortho-to-para ratio, which is three to one at room temperature and drops with decreasing temperatures. "In fact, certain regions of the universe exhibit ratios that are quite different from what you would expect," Horke says. "Yet, the specific reasons are unknown and lab-based experiments could provide new insights."

Back on Earth, the study may also help determine the structures of proteins – biomolecules that are essential to all life. A method known as nuclear magnetic resonance (NMR) spectroscopy reconstructs protein structures from the relative orientation of the nuclear spins of hydrogen and other atoms. "Para hydrogen has successfully been used to enhance the sensitivity of the NMR method," says Horke. "Thus, enriching para water in a protein's shell could become an interesting approach to improve NMR spectroscopy of these biological systems due to an almost natural environment."

Explore further: Researchers provide new information about mass spectrometry

More information: Separating Para and Ortho Water; D. A. Horke et al.; Angewandte Chemie International Edition, 2014; DOI: 10.1002/anie.201405986

Trennung von para- and ortho-Wasser; D. A. Horke et al.; Angewandte Chemie, 2014, DOI: 10.1002/ange.201405986

Related Stories

Researchers provide new information about mass spectrometry

October 15, 2007

Fresh data on mass spectrometry are presented in the report ‘Low-energy collision-induced fragmentation of negative ions derived from ortho-, meta-, and para-hydroxyphenyl carbaldehydes, ketones, and related compounds,’ ...

Water caged in buckyballs

May 20, 2014

In a new paper in the Journal of Chemical Physics, a research team in the United Kingdom and the United States describes how water molecules "caged" in fullerene spheres ("buckyballs") are providing a deeper insight into ...

Researchers 'cage' water to see it change form

June 16, 2014

(Phys.org) —Scientists are using a pioneering method of 'caging' and cooling water molecules to study the change in orientation of the magnetic nuclei at the centre of each hydrogen atom - a process which transforms the ...

Water molecules favor negative charges

July 16, 2014

(Phys.org) —In the presence of charged substances, H2O molecules favor associating with elements with a negative electrical charge rather than a positive electric charge. EPFL researchers have published a study on the subject ...

NASA image: Signs of deforestation in Brazil

August 20, 2014

Multiple fires are visible in in this image of the Para and Mato Grosso states of Brazil. Many of these were most likely intentionally set in order to deforest the land. Deforestation is the removal of a forest or stand of ...

Recommended for you

Force triggers gene expression by stretching chromatin

August 26, 2016

How genes in our DNA are expressed into traits within a cell is a complicated mystery with many players, the main suspects being chemical. However, a new study by University of Illinois researchers and collaborators in China ...

Isolation of Fe(IV) decamethylferrocene salts

August 29, 2016

(Phys.org)—Ferrocene is the model compound that students often learn when they are introduced to organometallic chemistry. It has an iron center that is coordinated to the π electrons in two cyclopentadienyl rings. (C5H5- ...

Bringing artificial enzymes closer to nature

August 29, 2016

Scientists at the University of Basel, ETH Zurich, and NCCR Molecular Systems Engineering have developed an artificial metalloenzyme that catalyses a reaction inside of cells without equivalent in nature. This could be a ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

KBK
1 / 5 (1) Sep 08, 2014
Look up people playing with 'charged' water and whatnot. magentics used to charge it, spin type devices,and so on. When looking at magnetism, electric fundamentals, van-der-waals, casimir, and much more (die gloken, etc) while considering their attempts and claims...you will find root cause in the same considerations as found here, in this article.

Discovery can and does come from outside science, every day. Science noting, and then organizing and quantifying it, has little to nothing to do with this 'external to science motherlode of lore'.

This plays directly into the complex physics of maxwell's full equations, not the edited/stunted ones that people are taught at this time.

The domino effect in the logic of this illustrates that many other obscure claims of oddities suddenly begin to gain more 'scientific' credence.

Always important to remember that science is the observationally based organized methodology and record system, it is not the reality itself.
Sean_W
5 / 5 (1) Sep 08, 2014
In ice the molecules are not directly interacting as randomly so would freezing be the best way to preserve the high or low ratio? Is the ratio an equilibrium state (dependant on temperature) which is reached over time. Why is the ratio not even? How fast does water return to the "normal" ratio when returned to warm and dense conditions--fractions of a second? Days?

Sounds like fascinating research.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.