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The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 15 (2010) pp 231-236

Raman Spectra of Homonuclear Diatomic Molecules - Resonance Raman Spectrum of Bromine Vapor

David R. Battiste, E. Alan Salter and Robert E. Barletta*

Department of Chemistry, University of South Alabama, Mobile, AL 36688,
Received December 20, 2010. Accepted March 4, 2010.

Published: 10 June 2010

Abstract. A laboratory experiment based on the resonance Raman spectrum of bromine vapor is described. This experiment has been integrated into the second semester of a two semester course in physical chemistry, which focuses on quantum mechanics, spectroscopy and statistical thermodynamics. During this experiment, students measure both the electronic absorption spectrum and the Raman spectrum of bromine vapor using a simple experimental arrangement described. From the data, students calculate molecular constants of the bromine molecule, i.e., force constant (k), the anharmonicity constant, xe, and the well depth, De. Further, students assess the degree of vibrational heating due to laser irradiation using the observed Stokes/anti-Stokes ratios for the fundamental vibration and overtone vibrations. Sample data obtained is included along with an experimental protocol suitable for student use. This experiment provides a comprehensive treatment of Raman and resonance Raman spectrometry and illustrates the effect of the population distribution of vibrational states on observed Raman intensities. As such, it provides the student of physical chemistry with a concrete example of the connection between spectroscopy and statistical thermodynamics.

Key Words: Laboratories and Demonstrations; physical chemsitry; quantum mechanics

(*) Corresponding author. (E-mail:

Article in PDF format (193 KB) HTML format

Supporting Materials:

The supporting file contains an experimental protocol for student use in conducting this experiment. (918 KB)


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