# THE GEOMETRY OF EXCITED ELECTRONIC STATES AND THE FRANCK-CONDON $PRINCIPLE^{*}$

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 Title: THE GEOMETRY OF EXCITED ELECTRONIC STATES AND THE FRANCK-CONDON $PRINCIPLE^{*}$ Creators: Coon, J. B.; DeWames, R. E.; Loyd, C. M. Issue Date: 1960 Publisher: Ohio State University Abstract: “A practical procedure for determining the geometry of excited electronic states of polyatomic molecules will be described and illustrated. The procedure requires a measurement of the relative intensities of a few selected bands arising from the vibrationless level of the ground electronic state. Using excited state normal coordinates $Q^{\prime}_{i}$; given $byQ^{\prime}_{i}=Q^{\prime}_{i}-C_{i}$, a given Condon overlap integral reduces to a function of one of the $C_{i}$. The relation between observed intensities and the overlap Integrals permits the calculation of the $C_{i}$ which specify, to the first approximation, the equilibrium configuration of the excited state relative to that of the ground state through a transformation $(X)^{\prime}^{\prime})=(A) \ (Q)^{\prime}^{\prime})$ where $Q^{\prime}_{i}=C_{i}$. A second approximation is based on excited state normal coordinates $Q^{\prime}_{i}$; calculated from the excited state geometry obtained in the first approximation. The $Q^{\prime}_{i}$; define a new transformation (A) which in turn gives the corrected excited state geometry. There are always at least four excited state models consistent with the observed intensities. In the normal coordinate calculations, only $A_{1}$ symmetry coordinates and their corresponding harmonic potential force constants need be considered.” Description: $^{*}$Supported by the Air Force Office of scientific Research. Author Institution: Department of Physics, A. and M. College of Texas URI: http://hdl.handle.net/1811/7921 Other Identifiers: 1960-B-5