The work of this paper is focused on the influence of rotational temperature on the emission spectra of the branches relatively to the head of band Q(0,0). After a description of the rotational states, we took into account the total angular momentum in the case where the electronic spin is neglected. We then determined the terms of energy and the wave number by defining the different levels of energy. We have also defined the selection rule for the different transitions by only taking into account the transitions which satisfy this rule and then three main branches are defined. Considering these strong branches, ten branches or wavenumbers have been defined. We have defined the distribution of line strengths or transition probability as a function of the rotational quantum number. Finally, we have determined the intensity of a rotational line based on the transitions between rotational levels belonging to two vibrational energy levels. The results show that the emission spectra is insensitive to rotational temperatures lower than 62.67 K for all the branches and to rotational temperatures higher than 850,000 K, 750,000 K, and 650,000 K respectively for the branches Q, P and R.

Energy Levels; Spectra; Rotational Temperature; OH-radical; Numerical Model.