Historical photograph of the Argon laser used in Raman scattering experiments. In such experiments, a scientist can learn about the atomic structure of a transparent solid or liquid by passing a laser beam through it. When the laser light goes through such a material, it displaces certain atoms and produces mechanical vibrations called phonons. A test instrument called a spectrometer detects these phonons and indicates their intensity and spacing data which are peculiar to the material being studied. The Argon Ion laser was invented in 1964 by William Bridges at Hughes Aircraft