ESS 51 F2013 lecture 15 spectroscopy Watenphul

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

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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...
View Full Document

Ask a homework question - tutors are online