We develop in this note a simple and practical method for the determination of the rotational temperatures based on the observation of molecular bands produced by the OH-radical. For this, we make an approach based on the concept of thermodynamic equilibrium and we proceed to a detailed study of OH. We carry out the simulation of this OH-radical by systematically assuming the different cases of Hund. We have revised the molecular constants of the literature related to OH-radical, and we have used the expressions of the rotational energy levels which are in good agreement with literature data. We have established the evolution of the rotational structures as a function of the simulation parameters. The comparison between the results of literature and the simulated results has allowed deducing the rotational temperatures by using Boltzmann method.

Energy Levels, Spectrum, Rotational Temperature, OH-radical