TAILIEUCHUNG - Introduction to Spectroscopy

The velocity at which radiation travels (or propagates) through a medium is dependent on the medium itself When radiation travels through a medium and does not undergo a frequency change, it cannot be undergoing a permanent energy transfer However, radiation can still interact with the medium – Radiation, an EM field, polarizes the electron clouds of atoms in the medium – Polarization is a temporary deformation of the electron clouds | a W VILLANOVA UNIVERSITY Introduction to Spectroscopy Lecture Date January 18th 2007 What is Spectroscopy The study of the interaction between radiation and matter Analytical spectroscopy as defined in this class covers applications of spectroscopy to chemical analysis 1 History of Analytical Spectroscopy 1666 Isaac Newton England shows that white light can be dispersed into constituent colors and coins the term spectrum - Newton also produced the first spectroscope based on lenses a prism and a screen 1800 W. Herschel and J. W. Ritter show that infrared IR and ultraviolet UV light are part of the spectrum 1814 Joseph Fraunhofer noticed that the sun s spectrum contains a number of dark lines developed the diffraction grating 1859 G. Kirchoff obtains spectra of the elements explains the sun s spectrum The Visible Spectrum of the Sun Black lines are absorption by elements in the cooler outer region of the star Figure from National Optical Astronomy Observatory Association of Universities for Research in Astronomy National Science Foundation http image_gallery html 2 History of Analytical Spectroscopy 1870 J. C. Maxwell formalizes and combines the laws of electricity and magnetism 1900 to present More than 25 Nobel prizes awarded to spectroscopists including - 1902 H. A. Lorentz and P. Zeeman - 1919 J. Stark - 1933 P. A. M. Dirac and E. Schrodinger - 1945 W. Pauli - 1999 A. Zewail Introduction to Spectroscopy The electromagnetic spectrum Each color you see is a specific narrow range of frequencies in this spectrum 475 510 570 Wavelength nml 550 475 510 570 650 Wavelength nm o 1 475 510 570 Wavelength nm 650 475 510 570 650 Wavelength nm Figures from NASA

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