Abstract: Based on the principle of electron spin resonance(ESR) a program for the spectral simulation of solution free radical has been developed written in advanced BASIC language. The electronic energy levels of free radical and their resonance lines are calculated using a first-order approximation theory by assuming a mixed lineshape of Lorentzian and Gaussian function. The range of nuclear spin is from 1/2 to 7/2. Up to 10 different kinds of non-equivalent nuclei are supported, but the number of equivalent nuclei, in principle, is unlimited. The program has been successfully performed on IBM-PC computer. In this paper two examples, the simulation of both the perylene cation radical and nitrobenzene anion radical, are presented.

Key words: ESR, Simulation, Solution free radical, Perylene, Nitrobenzene