Solve the Mystery of the Gases (2003)

What do CD and DVD players, grocery store bar code readers, metal cutting and welding tools, and ultra-delicate eye surgery tools all have in common? Right! They all make use of lasers. The laser was invented in 1958, and first, people didn't think it would be good for much. How wrong they were! Cutting through hundreds of layers of fabric once to make clothing. Carrying TV and telephone signals over fiber optic cable. Measuring distances for surveying tracts of land. These are just a few of the ways lasers make our daily lives easier, less expensive, healthier, more interesting, or just more fun. Lasers have also found great uses in space. For one thing, they can be used in a device called a spectrometer. A Spec-what-o-meter? What it can do: A spectrometer (spek-TROM-met-er) uses to identify the chemical composition of matter. For example, a spectrometer at sunlight that has passed through the air above a city can detect what gases the air contains (like carbon dioxide, nitrogen, oxygen, carbon monoxide, and pollutants like ozone and methane). A spectrometer can also tell us what materials are in the atmospheres of other planets, like Mars and Venus, or their satellites, like Saturn's moon, Titan, or Jupiter's moon, Europa. How it works: So, how does a spectrometer identify material just by looking light? Remember that photons, or particles, travel in waves. Different colors of have waves of different lengths. For example, red waves are longer than blue waves. White is made up of all the wavelengths mixed together. Even from the Sun or a bulb contains many different wavelengths. Atoms and molecules in solids, liquids, or gases produce or change in a unique way. When very hot, each emits a unique color of of an exact wavelength. For example, hot sodium street lights are yellow, and mercury athletic field lights are blue. When vaporized, or in the form of a gas, each absorbs that unique color of light, of an exact wavelength. In other words, every atom or molecule leaves a unique fingerprint as its spectrum. Emission spectrometers (like prisms) analyze emitted, or coming from some source, like sunlight, starlight, or from a hot, glowing gas. Strong colors of an exact wavelength reveal what kinds of matter the source is composed of. Absorption spectrometers look for missing, or absorbed colors in that has passed through a gas or vapor. Colors of an exact wavelength that are missing from this reveal what kinds of atoms and molecules the gas contains. The source could be the Sun or a laser. A laser spectrometer is a special type of absorption spectrometer that shines a laser beam through the gas. (More on lasers later.) Spectroscopy then, is a way of studying the wavelengths of coming from some material (like a star or a very hot metal) or passing through some material, like a gas. With this technique, scientists can tell what materials are burning (like in a star or a firework) just by examining the wavelengths of produced. Or, they can identify a cold (that is, non-glowing) gas by seeing what wavelengths are missing after has passed through it. What's more, if two or more kinds of materials are present, they can tell in what proportions they are mixed. If you want to know more about how spectroscopy works, check out The Space Place article entitled Taking Apart the Light, from the March 2002 issue of The Technology Teacher, now available on The Space Place Web site http://spaceplace.nasa.gov/teachers/eo3_spectroscopy.pdf. Get Those Waves Organized! Laser is an acronym of (short for) light amplification by stimulated emission of radiation. But what does this mean? What makes laser so different from ordinary light? …