There's a storm in your teacup that we barely understand. Water molecules move wildly, reaching out for each other, clinging and releasing themselves in unique ways that defy easy operation.
While physicists know that the phenomenon of hydrogen bonding plays an important role in water's many strange and wonderful configurations, some details of exactly how this works have remained rather vague.
An international team of researchers has taken a new approach to imaging the positions of the particles that make up liquid water. He captured their turbidity with femtosecond precision to reveal how hydrogen and oxygen were repelled within water molecules.
Their results may not help us make a better cup of tea, but they've gone a long way in uncovering quantum modeling of hydrogen bonds and have developed theories that potentially explain why water, so vital to life as we know it, has such intriguing properties.
"This really opened a new window to study water," says Xijie Wang, physicist at the U.S. Department of Energy's SLAC National Accelerator Laboratory. “Now that we can see hydrogen bonds moving, we want to relate these movements to a broader picture that can shed light on how water led to the origin and survival of life on Earth and inform the development of renewable energy methods. ”
In isolation, it is a three-way surveillance war over electrons between a single water molecule, two hydrogen atoms, and a single oxygen.
As you may remember from high school science, a water molecule consists of an oxygen atom (O) and two hydrogen atoms (H). Different H, which gives water its peculiar properties2They are interactions between O molecules – intramolecular forces called "hydrogen bonds". The positively charged hydrogen atoms in one molecule are attracted to the more negatively charged oxygen atoms in the other. This network of hydrogen bonds holds groups of water molecules together.
When you throw a few of these molecules together with enough energy, small changes in charge will adjust themselves accordingly, the same charges will separate and different charges will come together.
While this all sounds simple enough, the engine behind this process is anything but simple. Electrons converge under the influence of various quantum laws, so the closer we look, the less certain we can be about certain properties.
Previously, physicists relied on ultrafast spectroscopy to understand how electrons move in the chaotic strife of water, capture photons of light and analyze their signatures to map electron positions.
Unfortunately, this leaves out a very important part of the landscape – the atoms themselves. They yawn and sway at the same time, away from passive spectators, according to the changing quantum forces around them.
"The low mass of hydrogen atoms highlights their quantum wave-like behavior," says SLAC physicist Kelly Gaffney.
The team used something called the Megaelectronvolt Ultra-Fast Electron Diffraction Instrument, or MeV-UED, to gain insight into the arrangement of atoms.
This device at SLAC's National Accelerator Laboratory washes water with electrons that carry important information about the arrangement of atoms as they bounce off molecules.
With enough snapshots, it was possible to construct a high-resolution picture of hydrogen swinging as the molecules twist and bend around them, revealing how they drag oxygen from neighboring molecules towards them before violently pushing them back.
“This work is the first to directly show that the response of the hydrogen bond network to an energy impulse is critically dependent on the quantum mechanical nature of how hydrogen atoms split; network of water and hydrogen bonds,” says Gaffney.
Now that the tool has been shown to work in principle, researchers could use it to study the turbulent waltz of water molecules as pressures rise and temperatures drop, and watch how it responds to life-forming organic solutes or creates surprising new phases under exotic conditions.
A storm has never looked so graceful.
Günceleme: 30/08/2021 19:24
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