Quantum Tunneling Creates A Never Before Seen Shape For Water Molecules

New state of water: Strange 6-sided molecule found

 

A strange new behavior of water molecules has been observed inside crystals of beryl, a type of emerald, caused by bizarre quantum-mechanical effects that let the water molecules face six different directions at the same time.

Under normal conditions, the two hydrogen atoms in each water molecule are arranged around the oxygen atom in an open "V" shape, sometimes compared to a boomerang or Mickey Mouse ears.

But in a new experiment, scientists have found that hydrogen atoms of some water molecules trapped in the crystal structure of the mineral beryl become "smeared out" into a six-sided ring. 

The ring shape is caused by the "quantum tunneling" of the molecules, a phenomenon that lets subatomic particles pass or "tunnel" through seemingly-impossible physical barriers.

In this scenario, the atoms of the water molecule are "delocalized" among six possible directions inside natural hexagonal pores or channels that run though the crystal structure of the beryl, so it partially exist in all six positions at the same time, the researchers said.

Inside crystals 

Scientists from Oak Ridge National Laboratory (ORNL) in Tennessee and the Rutherford Appleton Laboratory in the United Kingdom observed the newly discovered effect in blue aquamarine crystals purchased at a gem show. Blue aquamarine; green and red emerald; pink morganite; gold heliodor; and clear goshenite gemstones are all varieties of the mineral beryl (beryllium aluminum cyclosilicate) with traces of other chemicals that give the crystals their characteristic colors.

"We chose beryl because it has a crystal structure that has channels in it, about 5 angstroms [5 ten-millionths of a millimeter] across — a little bit bigger than a water molecule — and it's known from spectroscopic data that natural beryls have water in them," said Larry Anovitz, a geochemist at ORNL and one of the authors of a paper on the new research. "We already know from lots of other studies that as you put water in smaller and smaller pores it starts to affect the properties of the water — the freezing point drops, the density changes, all sorts of things. So, we wanted to know, if you made that pore so small that you only can get a single molecule of water into it, what would that would do to the properties of water?"

What happened next was unexpected, Anovitz told Live Science.

"We knew that natural beryl would have water in these channels in the structure, so we could go and look at that and see what the properties were," he said. "But we didn't know that the properties would turn out to be so strange when we looked." 

Seeing a new state 

At ORNL's Spallation Neutron Source facility, after cooling the beryl crystals to very low temperatures, the scientists measured the lowest-energy states of the atoms in the trapped water molecules with neutron-scattering experiments, which use a beam of subatomic neutron particles to chart the motion of atoms and molecules.

"When we started looking at peaks in the inelastic neutron spectrum for this sample, we saw a number of peaks in the spectrum that, instead of getting bigger with temperature — which is what is expected to happen — they got smaller with temperature," Anovitz said.

"There are two ways this could happen — either by quantum tunneling or magnetic transitions — and we were able to prove that this is actually the quantum tunneling of the water molecules," he said.

Interactions between water molecules and the walls of the hexagonal channels usually force the water into the center of the channel, with both hydrogen "mouse ears" facing the same one of the six sides.

In their lowest energy states, the water molecules do not have enough energy to rotate to one of the adjacent positions.

But in the areas where the channels narrow so just a single water molecule can fit, the atoms in the water molecule can "tunnel" through the energy barrier that prevents rotation. And the new experiments reveal that the molecules were forming a "double-top" shape, with the proton nucleus of each hydrogen atom delocalizing into a six-sided ring around the central oxygen atom, the researchers said.

Measuring the molecules 

Alexander Kolesnikov, a physicist at ORNL and the lead author of the new paper, said additional studies at the Rutherford Appleton Laboratory had determined that the kinetic energy of the hydrogen protons in the six-sided water molecules was about 30 percent lower than in molecules of water in its normal state, or "bulk water."

"That is a direct indication that this is a quantum property due to the tunneling of water in this beryl channel," Kolesnikov told Live Science. "In classical terms, the kinetic energy would be expected to be something comparable to all other bulk water.

"This is not a new phase of water [like ice or steam] — it's not completely in the gas phase, but it's close to a gas phase," he added. "But at low temperatures, due to quantum delocalization, the kinetic energy of the protons significantly decreases, and they propagate under this [energy] barrier. So, I would say this is kind of a new state of the water molecule."

Anovitz said that quantum tunneling was known to occur in other substances but that the effect was usually limited to subatomic particles rather than larger particles like water molecules.

Quantum tunneling was also known to take place among hydrogen atoms in methyl-group molecules, which are arranged in a triangular pyramid shape around a carbon atom, but the molecules looked the same shape after the tunneling transition, he said.

"With water, when it's moving around this six-fold axis in the beryl channel, it doesn't look the same anymore — and that's something that's never been seen before," Anovitz said. 

Reference:

The findings were published April 22 in the journal Physical Review Letters.

Quantum Tunneling of Water in Beryl: A New State of the Water

Phys. Rev. Lett. 116, 167802

ONRL

Researchers Find New Phase of Carbon, Make Diamond at Room Temperature

Researchers from North Carolina State University have discovered a new phase of solid carbon, called Q-carbon, which is distinct from the known phases of graphite and diamond. They have also developed a technique for using Q-carbon to make diamond-related structures at room temperature and at ambient atmospheric pressure in air.

Phases are distinct forms of the same material. Graphite is one of the solid phases of carbon; diamond is another.

“We’ve now created a third solid phase of carbon,” says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of three papers describing the work. “The only place it may be found in the natural world would be possibly in the core of some planets.”

Q-carbon has some unusual characteristics. For one thing, it is ferromagnetic – which other solid forms of carbon are not.

“We didn’t even think that was possible,” Narayan says.

In addition, Q-carbon is harder than diamond, and glows when exposed to even low levels of energy.

“Q-carbon’s strength and low work-function – its willingness to release electrons – make it very promising for developing new electronic display technologies,” Narayan says.

But Q-carbon can also be used to create a variety of single-crystal diamond objects. To understand that, you have to understand the process for creating Q-carbon.

Researchers start with a substrate, such as such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon – elemental carbon that, unlike graphite or diamond, does not have a regular, well-defined crystalline structure. The carbon is then hit with a single laser pulse lasting approximately 200 nanoseconds. During this pulse, the temperature of the carbon is raised to 4,000 Kelvin (or around 3,727 degrees Celsius) and then rapidly cooled.

This operation takes place at one atmosphere – the same pressure as the surrounding air.

The end result is a film of Q-carbon, and researchers can control the process to make films between 20 nanometers and 500 nanometers thick.

By using different substrates and changing the duration of the laser pulse, the researchers can also control how quickly the carbon cools. By changing the rate of cooling, they are able to create diamond structures within the Q-carbon.

“We can create diamond nanoneedles or microneedles, nanodots, or large-area diamond films, with applications for drug delivery, industrial processes and for creating high-temperature switches and power electronics,” Narayan says. “These diamond objects have a single-crystalline structure, making them stronger than polycrystalline materials. And it is all done at room temperature and at ambient atmosphere – we’re basically using a laser like the ones used for laser eye surgery. So, not only does this allow us to develop new applications, but the process itself is relatively inexpensive.”

And, if researchers want to convert more of the Q-carbon to diamond, they can simply repeat the laser-pulse/cooling process.

If Q-carbon is harder than diamond, why would someone want to make diamond nanodots instead of Q-carbon ones? Because we still have a lot to learn about this new material.

“We can make Q-carbon films, and we’re learning its properties, but we are still in the early stages of understanding how to manipulate it,” Narayan says. “We know a lot about diamond, so we can make diamond nanodots. We don’t yet know how to make Q-carbon nanodots or microneedles. That’s something we’re working on.”

NC State has filed two provisional patents on the Q-carbon and diamond creation techniques.

North Carolina State University

Laser-wielding physicists seize control of atoms’ behavior

Physicists have wondered in recent years if they could control how atoms interact using light. Now they know that they can, by demonstrating games of quantum billiards with unusual new rules.

In an article published online Oct. 5 in Physical Review Letters, a team of University of Chicago physicists explains how to tune a laser to make atoms attract or repel each other in an exotic state of matter called a Bose-Einstein condensate. 

“This realizes a goal that has been pursued for the past 20 years,” said Cheng Chin, professor in physics, who led the team. “This exquisite control over interactions in a many-body system has great potential for the exploration of exotic quantum phenomena and engineering of novel quantum devices.

Many research groups in the United States and Europe have tried various ideas over the last decade. It was Logan Clark, a graduate student in Chin’s group, who came up with the first practical solution. He has now demonstrated the idea in the lab with cesium atoms chilled to temperatures just billionths of a degree above absolute zero, and the technique can be widely applied to other atomic species.

Clark compared the process to a billiards game, when one ball encounters another. “Normally, as soon as the surfaces touch, the balls repel each other and bounce away,” Clark said. In Chin’s lab, cesium atoms replace the billiard balls, and ordinarily they repel each other when they collide. But by turning up the laser while operating at a “magic” wavelength, Clark showed that the repulsion between atoms can be converted into attraction.

“The atoms exhibit fascinating behavior in this system,” he said. By exposing different parts of the sample to different laser intensities, “We can choose to make the atoms attract or repel each other, or pass right through each other without colliding.”

Alternatively, by oscillating their interactions, analogous to making the billiard balls rapidly grow and shrink while they roll, the atoms stick to each other in pairs.

The researchers explained two fundamental ways that lasers influence the atomic motion. One is to create potentials, like a bump or valley on the billiard table, proportional to laser intensity. The new way is to alter how billiard balls collide.

“We want our laser to control collisions, but we don’t want it to create any hills or valleys,” Clark said. When the laser is tuned to a “magic wavelength,” the beam creates no hills or valleys, but only affects collisions.

“This is because the magic wavelength happens to be in between two excited states of the atom, so they ‘magically’ cancel each other out,” he said.

Magic is a concept that has no place in science, though the word does enjoy fairly common use among atomic physicists. “Generally it is used to refer to a wavelength at which two effects cancel or are equal, in particular when this cancellation or equality is useful for some technological goal,” Clark said.

University of Chicago

Nanotechnology World Association

At near absolute zero, molecules may start to exhibit exotic states of matter

MIT researchers have successfully cooled a gas of sodium potassium (NaK) molecules to a temperature of 500 nanokelvin. In this artist's illustration, the NaK molecule is represented with frozen spheres of ice merged together: the smaller sphere on the left represents a sodium atom, and the larger sphere on the right is a potassium atom. Illustration: Jose-Luis Olivares/MIT

MIT team creates ultracold molecules

 

The air around us is a chaotic superhighway of molecules whizzing through space and constantly colliding with each other at speeds of hundreds of miles per hour. Such erratic molecular behavior is normal at ambient temperatures.

But scientists have long suspected that if temperatures were to plunge to near absolute zero, molecules would come to a screeching halt, ceasing their individual chaotic motion and behaving as one collective body. This more orderly molecular behavior would begin to form very strange, exotic states of matter — states that have never been observed in the physical world.

More details: http://www.nanotechnologyworld.org/#!At-near-absolute-zero-molecules-may-start-to-exhibit-exotic-states-of-matter/c89r/557837140cf2df2eae40ed3a