Helium emission and absorption spectra. When electrons in an element become excited (by heating), they enter higher energy orbits. When they return to their ground state they release the extra energy as light radiation at a specific wavelength. The wavelengths emitted by an element are characteristic of that element. A matching absorption spectrum occurs when light passes through a material and is absorbed by its atoms. The 12 lines of the visible helium spectrum correspond to wavelengths of 388.8, 447.1, 471.3, 492.1, 501.5, 504.7, 587.5, 667.8, 686.7, 706.5, 728.1 and 781.3 nanometres (nm). For this diagram with labelled lines, see C025/8080.