Spectroscopic studies of molecules observed in comets

The potential energy curves for the different electronic states of molecules like N2+, N2, OH and S2 observed in comets are constructed by using the Rydberg-Klein-Rees method as modified by Vanderslice et al. The ground state dissociation energies are determined by curve fitting technique using the five parameter Hulburt-Hirschfelder (H-H) function. The estimated dissociation energies are 8.587+/-0.248, 9.620+/-0.275, 4.308+/-0.118 and 4.325 +/-0.115 eV for N2+, N2, OH and S2 respectively. These values are in good agreement with the literature values. The r-centroids and Franck-Condon factors (FC factors) for the band system of A-X system of N2+ and A-X and B-X system of N2 molecules have been calculated employing approximate analytical methods of Jarmain and Fraser and Nicholls and Jarmain. The absence of the bands in these systems is explained.