The Iodine Spectrum

Introduction: Determining the iodine spectrum is a classic experiment in Physical Chemistry. This easily obtained spectrum demonstrates a number of important spectroscopic principles. The study of the experimental spectrum clearly shows the relationship between vibrational and electronic energy levels by introducing the concept of a vibronic transition, demonstrating the anharmonicity of vibrational energy levels; and providing the dissociative limit for the vibronic transitions. With some additional data analysis it is also possible to calculate the parameters for the Morse potential energy function of the excited electronic state, demonstrate the Franck-Condon principle, and compute Franck-Condon factors. This Mathcad document serves as a template for the calculation of the excited state Morse potential curve for iodine from an experimental spectrum. The template could also be used for calculating the excited state Morse potential for any diatomic molecule that has a well defined vibronic spectrum, e.g. Br 2 , or CO. Performance Objectives: After completing the work described in this document you should be able to: