1. Infrared Spectroscopy Antonella Magnelli

2. Development Discovered in 1800 but commercially available in 1940s Prisms Grating Instruments Fourier-transform spectrometers Tunable infrared lasers

3. Applications Qualitative Analysis Organic and Inorganic Functional Groups “Fingerprint Region” Pure Unknowns Quantitative Analysis A = log 10 (I 0 /I) A = log 10 (100/T) A(v) = a(v)bc Molecular Structure Light molecules examined in gas phase exhibiting rotational structure Estimates of temperature and pressure Other Applications Calculation of thermodynamic quantities Studies of intermolecular forces etc.

4. 3 Regions Near Infrared 4000-12,500 cm -1, or 0.75-2.5μm Excite harmonics of molecular vibrations and low- energy electronic transitions in molecules and crystals Source Detector

5. 3 Regions Mid Infrared 200-4000 cm -1, or 2.5-20μm Stretching and bending vibrations of molecules Source Detector

6. 3 Regions Far Infrared 10-200 cm -1, or 20-200μm Rotational transitions in gaseous molecules Low-frequency bending and skeletal vibrations Lattice modes in solids Source Detector

7. Absorption of IR Radiation Rotational and Vibrational changes Radiation absorbed  Rotation and Vibration Broad vibrational absorption bands for liquids or solids Change in Dipole Moment MUST occur to absorb IR radiation

8. Instrumentation Fixed Mirror Detector Sample ZPD  Beam Splitter Moving Mirror  Source

9. Instrumentation Radiation Sources Mid IR Sources Near IR Sources Far IR Sources Laser IR Sources Monochromators and Interferometers FT Spectrometers Interferometer Components

10. Instrumentation Detectors Bolometer Thermocouples Thermistors Golay Detector Pyroelectric Detector Photon Detector

11. References McDowell, Robin S. “Infrared Spectroscopy,” in AccessScience@McGraw-Hill, http://www.accessscience.com, DOI 10.1036/1097-8542.944700, last modified: March 22, 2002. http://www.accessscience.com Robinson, James W., Skelly Frame, Eileen M., Frame, George M. (2005). Ungergraduate Instumental Analysis. 6 th Ed.