Rice University physicists have gone to extremes to prove that Isaac Newton’s classical laws of motion can apply in the atomic world: They’ve built an accurate model of part of the solar system inside a single atom of potassium.
In a new paper published this week in Physical Review Letters, Rice’s team and collaborators at the Oak Ridge National Laboratory and the Vienna University of Technology showed they could cause an electron in an atom to orbit the nucleus in precisely the same way that Jupiter’s Trojan asteroids orbit the sun.
The findings uphold a prediction made in 1920 by famed Danish physicist Niels Bohr about the relationship between the then-new science of quantum mechanics and Newton’s tried-and-true laws of motion.
“Bohr predicted that quantum mechanical descriptions of the physical world would, for systems of sufficient size, match the classical descriptions provided by Newtonian mechanics,” said lead researcher Barry Dunning, Rice’s Sam and Helen Worden Professor of Physics and chair of the Department of Physics and Astronomy. “Bohr also described the conditions under which this correspondence could be observed. In particular, he said it should be seen in atoms with very high principal quantum numbers, which are exactly what we study in our laboratory.”
… They succeeded by applying a radio frequency field that rotated around the nucleus itself. This field ensnared the localized electron and forced it to rotate in lockstep around the nucleus.
A further electric field pulse was used to measure the final result by taking a snapshot of the wave packet and destroying the delicate Rydberg atom in the process. After the experiment had been run tens of thousands of times, all the snapshots were combined to show that Bohr’s prediction was correct: The classical and quantum descriptions of the orbiting electron wave packets matched. In fact, the classical description of the wave packet trapped by the rotating field parallels the classical physics that explains the behavior of Jupiter’s Trojan asteroids.
Jupiter’s 4,000-plus Trojan asteroids — so called because each is named for a hero of the Trojan wars — have the same orbit as Jupiter and are contained in comma-shaped clouds that look remarkably similar to the localized wave packets created in the Rice experiments. And just as the wave packet in the atom is trapped by the combined electric field from the nucleus and the rotating wave, the Trojans are trapped by the combined gravitational field of the sun and orbiting Jupiter. …
via Rice University | News & Media.