Abstract: A method and apparatus for the quantitative and qualitative analysis of the elemental composition of materials in concentrations as low as a few atoms, or molecules, per cubic centimeter. When introduced into a gas stream containing an excess of an energetic metastable species of nitrogen or noble gas, the material, if atomic, is rapidly and repeatedly excited, or, if molecular, it is decomposed and subsequently certain component atoms of the molecule are excited, and thereupon fluoresce at their characteristic wavelength(s). The wavelength(s) and intensity of the emitted light (fluorescence) are determinative respectively of the identity and the concentration of the atoms of the different elements present.