Scientists first made lasers using solid crystals or mixtures of gasses in 1960. Lasers using liquid dyes were developed in 1965. Dyes proved useful for making lasers that could be tuned over a range of light frequencies, somewhat similar to a musical instrument that can be tuned to different sound frequencies. Each of these five glass ampoules contains about 1 microgram of dye in a solution with 50 milliliters of ethyl alcohol. The glass ampoules are storage containers. In operation a dye is typically pumped through the laser apparatus.
These dye samples come from the Atomic Vapor Laser Isotope Separation Program (ALVIS) at Lawrence Berkeley National Laboratory. Light from a copper-vapor laser changed color (or frequency) by passing through a given dye, resulting in a laser beam with a specific frequency. Different frequencies equal different energy levels. Since atoms absorb energy at different frequencies, changing the laser light's color is a good way to impart just the right amount of energy needed to separate atoms such as isotopes that are almost, but not quite, identical.
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