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Fluorescence and Light Scattering
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Abstract
This experiment allows students to discover the fundamental experimental difference between fluorescence and light scattering; namely, that the wavelength of fluorescence is independent of the excitation wavelength whereas the wavelength of scattered light increases with increasing excitation wavelength. The students use this fact to identify the fluorescence, Rayleigh scattering, and Stokes Raman scattering bands of an aqueous solution of fluorescein. The wavenumber difference of the Raman scattering peak of the solvent water is then calculated and shown to agree well with the wavenumber of infrared absorption of liquid water at 3400 cm-1. The good agreement of the two values is explained by the initial and final energy levels being very similar in both cases, although the energy pathway followed is different for the two processes. Finally, the students predict the expected position of the anti-Stokes Raman scattering peak of water and show that it is not observable owing to the small population of the v = 1 vibrational state. The experiment requires inexpensive nonhazardous chemicals and is extremely reliable. It links three different spectroscopic techniques that are usually taught separately, fluorescence, Raman scattering, and infrared absorption, and encourages the development of students' fundamental understanding of spectroscopy in general.
Keywords (Audience):
Second-Year UndergraduateKeywords (Domain):
Laboratory InstructionKeywords (Pedagogy):
Hands-On Learning / ManipulativesKeywords (Subject):
Fluorescence SpectroscopyCiting Articles
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This article has been cited by 3 ACS Journal articles (3 most recent appear below).
Understanding Fluorescence Measurements through a Guided-Inquiry and Discovery Experiment in Advanced Analytical Laboratory
Grazyna Wilczek-Vera and Eric Dunbar SalinJournal of Chemical Education2011 88 (2), 216-219Understanding Fluorescence Measurements through a Guided-Inquiry and Discovery Experiment in Advanced Analytical Laboratory
Grazyna Wilczek-Vera and Eric Dunbar SalinJournal of Chemical Education2011 88 (2), 216-219An experiment on fluorescence spectroscopy suitable for an advanced analytical laboratory is presented. Its conceptual development used a combination of the expository and discovery styles. The “learn-as-you-go” and direct “hands-on” methodology applied ...
Modern Developments in the Physical Chemistry Laboratory
Samuel A. Abrash2007 973 (), 115-151Modern Developments in the Physical Chemistry Laboratory
Samuel A. Abrash2007 973 (), 115-151Developments in the physical chemistry laboratory since the publication of the germinal text by Schwenz and Moore (1) are categorized and reviewed. The categories examined include modern instrumentation, current topics in chemistry, integrated ...
Laser-Induced Fluorescence in Gaseous I2 Excited with a Green Laser Pointer
Joel TellinghuisenJournal of Chemical Education2007 84 (2), 336Laser-Induced Fluorescence in Gaseous I2 Excited with a Green Laser Pointer
Joel TellinghuisenJournal of Chemical Education2007 84 (2), 336The use of a green laser pointer to excite fluorescence in gaseous I2 results in an unexpected behavior: on transiting the cell, the beam alternately appears brightly and vanishes completely. This behavior is attributed to temporal changes in the laser’...
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- Received: August 03, 2009
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