Posts Tagged ‘quantum uncertainty’
For the First Time, Scientists Watch Electrons Move in Real Time
Using ultra-short flashes of laser light, scientists from the Max Planck Institute of Quantum Optics in Germany and Lawrence Berkeley National Laboratory in Berkeley, Calif., were able to time oscillations between valence electrons' quantum states.
Chemical reactions happen because of the dynamics of valence electrons, the ones in the outermost orbit of an atom. If you can watch them move, you can understand their mechanics and learn how they combine with other atoms to make up everything around us. But electrons move pretty fast, so this has been impossible until now.
The team used lasers that can work in the 100-attosecond time scale -- an attosecond is 10-18 seconds, a quintillionth of a second. They measured the movement of valence electrons in a form of ionized krypton that had one electron removed.
Berkeley Lab's news site provides some in-depth descriptions, but basically what happened is that scientists measured the continued flopping of electrons between two quantum states. These valence shell oscillations cycled in a little over six femtoseconds. Using much faster attosecond laser pulses, the team was able to essentially capture this oscillation in action. The work is reported in this week's edition of the journal Nature.
The Berkeley Lab test simply proves that scientists can see these electrons move. But the finding can be applied to any problem in the physics and chemistry of liquids, solids, biological systems -- basically everything, according to Stephen Leone of Berkeley Lab's Chemical Sciences Division.
"(It will) allow us to unravel processes within and among atoms, molecules, and crystals on the electronic timescale," he says.
As Berkeley Lab's news writer notes, this would have been previously impossible with the "comparatively languorous femtosecond timescale."
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Elusive Flowing Supersolids May Actually Be Quantum Plastics, New Paper Says
In the supersolid state, which scientists have ben trying to glimpse for years, matter retains the lattice-like structure it possesses as a solid, but it stops being rigid, meaning there is less friction. Instead, it flows like a liquid.
To look for this odd behavioral change, scientists have been studying a type of helium and making it very cold, bringing it to within a fraction of absolute zero.
In 2004, scientists figured out a way to detect supersolid helium by filling a special rotating pendulum and watching how it spun as the helium cooled. They figured the rotation speed would change when the helium became a supersolid rather than a regular solid, because of that loss of friction. It did change, and later experiments replicated the results.
But now, Cornell professor John Reppy says that change in rotation isn't necessarily because the helium became a supersolid. Instead, he says, meet quantum plastic.
Reppy says it's possible the normal helium simply deformed as the pendulum twisted. Helium-4, which is used in the experiments, has some inherent defects that change its behavior at different temperatures, making it wobbly. Reppy says that as the temperature rises, these defects get even more wobbly, thus making helium's structure less rigid. Therefore, its changed, bendy structure at ultra-cold temperatures is not necessarily because of supersolidity. Rather, Reppy says, it's more like plastic.
More research is needed before scientists can be sure who's right, and whether supersolidity or quantum plasticity is the culprit.
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