The Balmer series is the portion of the emission spectrum of hydrogen that represents electron transitions from energy levels n > 2 to n = 2. These are four lines in the visible spectrum. They are also known as the Balmer lines.
The four visible Balmer lines of hydrogen appear at 410 nm, 434 nm, 486 nm and 656 nm. These are caused by photons produced by electrons in excited states transitioning to more stable energy levels. There are also multiple ultraviolet Balmer lines that have wavelengths shorter than 400 nm. The spectrum becomes continuous approaching 364.6 nm (ultraviolet).
Note: While Balmer discovered four visible lines, five other hydrogen spectral series were later discovered for values of n besides 2.
The Balmer series in especially important in astronomy. The lines are seem emitted by many stellar objects because most of the universe consists of the element hydrogen. The series is used to help determine the surface temperature of stars.
- Nave, C. R. (2006). "Hydrogen Spectrum." HyperPhysics. Georgia State University.