tailieunhanh - Electronic Spectroscopy 1

Deviations from Beer’s law (. deviations from the linearity of absorbance vs. concentration): – Intermolecular interactions at higher concentrations – Chemical reactions (species having different spectra) – Peak width/polychromatic radiation Beer’s law is only strictly valid with single-frequency radiation Not significant if the bandwidth of the monochromator is less than 1/10 of the half-width of the absorption peak at halfheight. | a W VILLANOVA UNIVERSITY Optical Electronic Spectroscopy 1 Lecture Date January 23rd 2008 1 What is Electronic Spectroscopy Spectroscopy of the electrons surrounding an atom or a molecule electron energy-level transitions Atoms electrons are in hydrogen-like orbitals s p d f The Bohr model for nitrogen Molecules electrons are in molecular orbitals HOMO LUMO . The LUMO of benzene Optical Electronic Spectroscopy Definition Spectroscopy in the optical UV-Visible range involving electronic energy levels excited by electromagnetic radiation often valence electrons . This lecture is related to the high-energy non-optical electron spectroscopy covered in the X-ray lecture Methods - Atomic absorption - Atomic emission ICP-OES - Molecular UV-Visible absorption - Luminescence Fluorescence Phosphorescence 2 Definitions of Electronic Processes Emission radiation produced by excited molecules ions or atoms as they relax to lower energy levels. Absorption radiation selectively absorbed by molecules ions or atoms accompanied by their excitation or promotion to a more energetic state. Luminescence radiation produced by a chemical reaction or internal electronic process possibly following absorption. Ccnliriuous Sfjet IriJTi More Electronic Processes Fluorescence absorption of radiation to an excited state followed by emission of radiation to a lower state of the same multiplicity - Occurs about 10-5 to 10-8 seconds after photon absorption Phosphorescence absorption of radiation to an excited state followed by emission of radiation to a lower state of different multiplicity - Occurs about 10 to 10-5 seconds after photon absorption

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• technology petrochemical
• oil and gas transport
• geological drilling
• oil lubrication
• Electroanalytical Chemistry
• ohmic Potential
• oil refining processes
• petrochemical organic
• petrochemical
• Nanomaterials
• polymetallic deposition
• compressor oil
• geological survey standards
• curriculum oil
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• Oil and Lubricants
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