Estimation of potential energy curves, dissociation energies, Franck-Condon factors and r-centroids of comet interesting molecules

The experimental potential energy curves for the different electronic states of molecules like CN, CO and CS 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 7.63 +/- 0.187, 10.95 +/- 0.224 and 7.27 +/- 0.152 eV for CN, CO and CS respectively. These values are in good agreement with the literature values. Estimated dissociation energies of CN, CO and CS are used in the relation given by Gaydon and ionization potentials are evaluated for CO and CS molecules. The estimated ionization potentials are 13.92 and 12.15 eV for CO and CS molecules respectively. The r-centroids and Franck- Condon factors (FC Factors) for the band system of a (3)Pir - X(1)Sigma(+) (a - X) and A(1)Pi- X(1)Sigma(+) (A- X) of CN, A(2)Pi(i) - X(2)Sigma(+) (A - X) and B(2)Sigma(+)-X (2)Sigma(+) (B - X) of CO and a (3)Pi(r) - X(1)Sigma(+) (a - X) of CS molecules have been calculated employing an approximate analytical methods of Jarmain and Fraser and Nicholls and Jarmain. The absence of the bands in these systems are explained.