2 Objectives

A pedagogical physical chemistry laboratory exercise developed to aid students to analyse Electron Paramagnetic Resonance (EPR) Spectra of organic free radical is presented. The exercise is based on a tutorial-simulator set that allows to study first-order isotropic systems. The material consists of: a) a tutorial that includes a brief theoretical introduction, a set of EPR spectra in progressive difficulty and several tables to be filled out by the students, and b) a spectra simulator that can be used independently or interconnected with the tutorial. Both tutorial and simulator are free Internet-accessible using a standard Web browser.

The main purposes of this tutorial are:

1. Understand elementary notions about Electron Paramagnetic Resonance (EPR) spectroscopy.
2. Learn the use of a program for the simulation of EPR spectra.
3. Interpret experimental first order spectra of organic free radicals to obtain an estimated set of magnetic parameters (coupled nuclei, spins, hyperfine splitting (hfs), $\ldots$).
4. Introduce in the simulation program the estimated magnetic parameters to obtain the simulated spectrum. Refine the magnetic and graphical parameters in order to obtain, by comparison with the experimental spectrum, the correct interpretation.