ESS 51 F2013 lecture 15 spectroscopy Watenphul

Spectroscopic methods 107ev 105ev 102ev 1ev 102ev

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Unformatted text preview: 0–8eV energy differences between excited and ground core nuclear states Mössbauer spectroscopy iden6fica6on of valence states (e.g. Fe2+/Fe3+), site occupancy Summary – Spectroscopic methods Spectroscopic methods are o^en named a^er •  the type of interac6on or effect that happens between radia6on and material e.g. emission/absorp6on spectroscopy e.g. Raman, Mössbauer spectroscopy •  the range of the electromagne6c spectrum the incident radia6on originates from e.g. infrared, UV-­‐VIS, X-­‐ray spectroscopy Spectroscopic methods probe the short-­‐range order of certain atoms, whereas diffrac6on studies the long-­‐range order. Infrared (IR) spectroscopy IR spectroscopy, also called vibra6onal spectroscopy, uses the infrared range of the EM spectrum to probe the vibra6onal behavior of minerals. IR radia6on range is o^en divided in 3 subcategories Near-­‐IR: 800 – 2500 nm (12500 – 4000 cm–1) Mid-­‐IR: 2500 – 25000 nm (4000 – 400 cm–1) Far-­‐IR: 25000 – 109 nm (400 – 10 cm–1) ν [cm-­‐1] = 107/ λ [nm] applica6ons common in mineralogy: mineral iden6fica6on quan6fica6on of molecule groups, e.g. OH, CO3, NH4 phase transi6on with P and T Infrared (IR) spectroscopy IR spectroscopy is an absorp6on technique. •  Radia6on with frequencies in the IR range is passed through a sample. •  Molecules, atomic groups, and even the whole laice may interact with the radia6on and partly absorb it. •  This promotes the atoms from their ground to the excited vibra6onal state. detector IR source sample Molecular vibra6ons A molecule of N atoms has 3N degrees of freedom. The number of vibra6onal modes is given by 3N-­‐6, in case of a linear molecule 3N-­‐5. Examples...
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This document was uploaded on 04/03/2014.

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