Atomic Emission Spectrum
The pattern of discrete wavelengths emitted when excited atoms of an element return to lower energy states.
Formula / equation
ΔE = hν
Unit
nm
In depth
Because energy levels are quantised, each element emits a unique set of sharp lines that acts as an atomic fingerprint. The technique identifies elements in samples and in starlight alike, and the study of hydrogen's line series directly inspired the Bohr model.
Examples in the real world
Sodium's intense yellow doublet at 589 nm in a flame test; helium was discovered in the Sun's spectrum before being found on Earth.