Spectral emission line

A very small range of wavelengths, over which the intensity of electromagnetic radiation is much greater than the surrounding, continuous spectrum. Discrete emission lines are produced by electrons in atoms and molecules dropping into lower energy quantum states and emitting photons of characteristic electromagnetic radiation. A spectrum with just spectral emission lines is called a line spectrum. The atomic spectra of all the elements are well documented, and Lockyer and Ramsey even identified a new element - helium - from hitherto unknown spectral lines in light from the Sun.