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Vibronic Spectra of Diatomic Molecules and the Birge-Sponer Extrapolation: BirgeSponer.mcd

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Theresa Julia Zielinsi

Department of Chemistry, Medical Technology, and Physics, Monmouth University, West Long Branch, NJ 07764-1898

George M. Shalhoub

Department of Chemistry, La Salle University, Philadelphia, PA 19141

J. Chem. Educ., 1998, 75 (9), p 1192

DOI: 10.1021/ed075p1192.2

Publication Date (Web): September 1, 1998

Abstract

The goal of this document is to examine the potential energy curve for both the ground and excited states of an electronic transition in order to set the stage for a Birge-Sponer determination of the D_o and D_e dissociation energies of the excited state of a diatomic molecule from experimental UV-vis spectral data. This document takes advantage of the live symbolics and optimize features of Mathcad PLUS 6 to present a derivation of the Birge-Sponer equations. The documentcontains ample student exercises to foster reflection and learning of the spectroscopic concepts. After using this document students will be able to: explain the relationship between the potential energy curves for excited and ground states in a molecule; explain the significance of each parameter in a Morse potential energy function; and use a Birge-Sponer plot to determine dissociation energy of an electronic excited state of a diatomic molecule. This document will prepare students for analysis of the vibronic spectrum of iodine or some other diatomic molecule. The Iodine Spectrum document (below) is the companion template for the analysis of the UV-vis spectrum of a diatomic molecule.