How an Atomic Clock Works

Resonant Frequencies

The first step in making an atomic clock work comes in the form of a measurement. The atomic resonance (between the nucleus of an atom and its electrons) must be determined. This is typically accomplished by means of a crystal oscillator, a device which can measure the atomic resonance.

Oscillations

The most important thing to understand when it comes to atomic clocks is the principle of oscillations. Just as a normal clock measures time via a hairspring and a balance wheel, an atomic clock measures time via the nucleus and the electrons of an atom. Both are measurements derived from oscillations. Though several types of atomic clocks exist (meaning simply atomic clocks that employ the use of different atomic elements, usually cesium, rubidium or hydrogen), this form of measurement remains the same: the oscillation between the electrons and the nucleus of the atom.

Locking Frequencies

The element is heated and the atoms pass through a tube in a vacuum, through a magnetic field. The magnetic field filters out atoms of the appropriate energy state, which are then passed through another field---a microwave field. The microwave energy is maintained within a certain range of frequencies. When the microwave frequency is right on target, a detector (at the end of the tube) "peaks," locking this microwave frequency in---and ensuring a consistent set of oscillations. This number is applied mathematically to measure seconds.

References

• National Institute of Standards and Technology.
• In-Depth Info.