Physics for the 21st Century logo

Interactive Lab

New Physics at the Intermediate Scale:
Laser Cooling

Note: Units 4 through 9 make use of this interactive lab to demonstrate concepts relevant to physics on the atomic scale.

Laser Cooling
Launch Interactive Lab

Electrons in an atom occupy discrete energy levels. When a photon hits the atom, if it has precisely the energy that corresponds to the difference between two electron energy levels, the atom will absorb the photon—and an electron in the lower level will jump to the higher level. When this happens, the atom gets a push in the direction the photon was travelling. When the electron drops back to the lower level, the atom re-emits the photon, and it gets another push, but in a random direction. Absorbing and re-emitting photons many times per second, the net result is that the atoms are pushed away from the source of light. In this lab, we manipulate a sample of fast-moving Ytterbium (Yb) atoms with a laser to prepare them to be captured in a trap.