Calculations of vibrational-rotational coupling constants in diatomic molecules

Vibrational-rotational coupling in diatomic molecules has been studied by three different approaches through the solution of Schroedinger equation with a new potential. In the first and second approaches called, respectively, the closed-form method and the factorization method, analytical expressions for the energy levels, wave functions and various spectroscopic constants viz., αsub(e) and ωsub(e)xsub(e) have been derived. In the third method, the said potential has been treated as the Morse one with some perturbations added to it, and the perturbation method has been employed to determine the energy levels and wave functions as corrections to those for the Morse potential. In this calculation a harmonic-oscillator wave function has been used as the unperturbed wave function. (author)