INFRARED SPECTROSCOPY (IR) Theory and Interpretation of IR spectra ASSIGNED READINGS • Introduction to technique 25 (p. 833-834 in lab textbook) • Uses of the Infrared Spectrum (p. 847-853) • Look over pages 853-866 after viewing this presentation for additional examples of various functional groups. Wavelength, λ (lambda), is the Part 2: Introduction to Molecular Spectroscopy: An introduction to the different types of molecular spectroscopic analysis, including UV-Vis, fluorescence, IR, MS and NMR, describing the basic principles of each technique and practical considerations including sample preparation. Infrared Spectroscopy generally refers to the analysis of the interaction of a molecule with infrared light. Spectroscopy: an Historic Journey (pre-history) Overview This course is targeted to advanced level undergraduate students (Bolonha 2th cycle) in Chemistry, Physics or Bio-Sciences and Freshmen PhD Students aiming to get a general overview of molecular spectroscopy. one another. Spectroscopy deals with the study of interaction of electromagnetic radiation with matter. Lecture 3 Basics of Spectroscopy . Interaction of light with a sample can influence the sample and/or the light. 5.33 Lecture Notes: Introduction to Spectroscopy Page 2 1 What does a spectrum measure? It is measured in Hz, where 1 Hz = 1 cycle/sec. • bending vibrational modes lead to much weaker Raman signals and are often quite strong in IR spectroscopy. Return to this later, specific use • Information on rotational and vibrational levels • Raman effect small but accessible by use of lasers • Complementary information to IR spectroscopy phomonuclear diatomic molecules, low frequency range • In situ analysis of organic and inorganic compounds • Analysis of aqueous solutions and solids (powders) Regions: -- near IR (800-2500 nm — quartz optics/W-I lamp, diode or thermal detect) anharmonic vib, overtone and combination bands. Why Raman spectroscopy? Infra Red Spectroscopy Introduction: The absorption of infra-red radiations causes the various bands in a molecule to stretch or bend w.r.t. Mid infra red region 2.5 – 1.5 micron Vib-Roto Spec. Infrared Spectroscopy is the analysis of infrared light interacting with a molecule. Far IR-Region 15 – 200 micron Overtone or harmonic light having a longer wavelength and a lower frequency than visible light. • a molecule can have both IR and Raman signals at the same frequency, though if the Raman signal is strong, the corresponding IR … Method involves: (1) excitation and (2) detection. Lecture Notes Chem 524 – IR spectra (Part 16)- 2013 For HTML of 2005 notes, click here XII. Near IR-Region 0.8 – 2.5 micron Rotational Spec. The basic idea: Light (E.M. wave) In most spectroscopies, we characterize how a sample modifies light entering it. IR spectroscopy (which is short for infrared spectroscopy) deals with the infrared region of the electromagnetic spectrum, i.e. Frequency, ν (nu), is the number of wave cycles that pass through a point in one second. Resources: IR and Raman Spectroscopy overview Powerpoint- FT-IR. Infrared Spectroscopy — focus on vibrational transitions (Read Chap 14) A. 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