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spectroscopy ppt.pptx
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- 2. CONTENTS • What isSpectroscopy? • Types of spectroscopy • Uses and Applications • Conclusion • Reference 2
- 3. WHAT IS SPECTROSCOPY? •Spectroscopy deals with the interaction of electromagnetic radiation with matter • Used to extract very useful information like structural and other physico-chemical properties of molecules. • Spectroscopy is the most imperative and promising tool for the structural investigation of chemically relevant systems. 3
- 4. THE INTERACTION OFRADIATION WITH MATTER 4
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- 7. • Electromagnetic radiationsare produced by the oscillations of electric and magnetic dipoles residing in the atom. • The most important consequence of electromagnetic interaction is that energy is absorbed or emitted by the matter in discrete amounts called quanta. • Spectroscopic methods are generally used to measurer the energy difference between various molecular energy levels and to determine the atomic and molecular structures. 7
- 8. Electromagnetic waves travelat the speed of light and their frequency and wavelength can be determined by the formulas: where 'c' is the speed of light in meters per second, lambda λ is the wavelength in meters frequency is in cycles per second. 8
- 9. Molecule contains : •Translational energy • Rotational energy • • Vibratioal energy • Electronic energy • All except the Translational energy are quantized • Energy(molecule )= E(rot )+ E(vib )+ E(elec ) 9
- 10. THE INTERACTION OFRADIATION WITH MATTER DEPENDS UPON BOTH RADIATION PROPERTIES AND STRUCTURAL PARTS OF THE MATERIALS INVOLVED. THIS INTERACTION BETWEEN MATTER AND RADIATION LEADS TO A VARIETY OF SPECTRA. 10
- 11. THREE TYPES OFTHE ABSORPTION SPECTRUM: Nuclear spin states Electronic energy levels Infrared Radio frequency Ultraviolet- visible Absorptionof Electromagnetic Radiation Results inTransition Between Region ofthe Electromagnetic Spectrum Nuclear magnetic resonance Infrared Ultraviolet- visible Type of Spectroscopy Frequency (hetz) 2.5 x1014-1.5x1015 3 x107-9x108 1 x1013 -1x1014 Vibrational energy levels 11
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- 14. INFRARED SPECTROSCOPY Far-Infrared (400-33cm-1): vibrations of molecules containing heavy atoms, molecular skeleton vibrations and crystal lattice vibrations Mid-Infrared (4000-400 cm-1): useful for organic analysis Near Infrared (12820-4000 cm- 1): overtones; very useful for quantitative analysis 14
- 15. REQUIREMENTS FOR VISIBILITYIN THE IR REGION (selection rules) • A change in dipole moment, whether it is induced or permanent. Heteronuclear Diatomicmlecules E.g HCl, HBr etc N2, F2, etc. are inactive in the IR. • Resonant frequencies that are in the infrared frequency range of 100−4000 cm−1. • After the absorption of radiation only transition for which v=(+)(-) i.e, transition from=0 to V=1(change in vibration quatum number between two vibrational energy levels) 15
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- 17. CHANGE IN DIPOLEMOMENT IN TRIATOMIC MOLECULES 17
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- 22. Infrared Spectroscopy Infrared spectrumof 3-methyl-2-butanone. • Infrared spectrum of 3-methyl-2-butanone. Fingerprint Region: Highly Complex and Unique for Every Molecule C-H Stretching C=O Stretching 22
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- 30. UV spectrum ofacetone 30
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