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Unformatted text preview: EPS 102 Lecture 3 Tuesday, January 27 th 2009 Fluorescent or neon lamps are where ions are at high enough temperatures to emit light. Outermost electrons get launched off Argon atoms, and the Argon atoms are left behind with positive electrical charged. Magnets can be used to accelerate these charged atoms. This tube has to be mostly empty, though, like a vacuum. A magnet is used to deflect this beam of high temperature Argon atomed and the amount of deflection is dependent on the mass. Less massive get deflected more, and this process is called a mass spectrometer. You have an electrical counter that counts how many ions hit the counter, and it gives the relative abundances (it is hard to measure absolute abundance). Radioactive decays usually measure relative abundances. For example, you could have a detector that collects the Argon beam of atoms. it could take about half an hour. You would want to measure some other Argon isotopes and the ratios of these things to each other. I t is worth in investing a bunch of collectors and do multiplexing, instead of measuring a series of items one at a time, you measure all of them in parallel or all of them simultaneously. You can line these detectors up and then let them catch the atoms. I t is a multi collector system that collects all of the isotopes. You reduce the time for collection and you can measure the relative abundances and see when just enough data has been received. The earliest homosapiens were in eastern Africa in the r ift region. Geochronologists have dated these early fossils to look at the evolution of humans. What elements makes a good radioactive decay scheme? You need a reasonable half life. For an ancient material, you want long half lives, etc You also need sufficicent abundance of the radioactive isotope that is decaying, the daughter product has to be stable. We fitted data on a straight line, and what we are doing is looking at the amount of decay product as a function of different radioactive isotopes. Some contain a lot and some contain a little radioactivity. Minerals with a little shift a little. Minerals with a lot create a lot of decay product. The slope of the line gives the age and the create a lot of decay product....
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- Spring '08