Why Do Spectral Lines Have a Linewidth?

Volker B. E. Thomsen
Spectro Analytical Instruments, Fitchburg, MA 01420
J. Chem. Educ., 1995, 72 (7), p 616
DOI: 10.1021/ed072p616
Publication Date: July 1995

Abstract

Any discussion involving spectral wavelength scans in introductory chemistry or instrumental methods classes runs the risk of encountering the following very good question: Why do spectral lines have a certain width rather than being straight lines on the scan? Theoretically, shouldn't each electron energy-level transition result in a spectral line at a single wavelength, corresponding to the difference in energy between the levels. Why the spread?Provided is a pedagogically useful introduction to the physical principles involved in the natural linewidth and Doppler broadening. Lorentz broadening is also briefly discussed. Also of interest from a teaching standpoint is the number of physical principles that can be addressed or reviewed under this single topic such as Planck's law and the Heisenberg uncertainty principle.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Analytical Chemistry

Keywords (Subject):

NMR Spectroscopy
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  • Received: August 03, 2009

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