Abstract: In this paper, linear harmonic oscillator model and space rotor model are used in combination to analyze the diatomic molecules under disturbance. It is a vibration plus rotation system. The energy eigen-values and eigen-functions of the system are calculated by solving the Schrodinger equation. The ground state energy and the degeneracy of eigen-values of the system are analyzed. Considering the weak external electric field, the first-order correction (zero), the second-order correction of eigen-values and the first-order correction of eigen-functions for the system are calculated for the non-degenerate case with zero angular quantum number by using the non-degenerate stationary perturbation theory.

Key words: linear harmonic oscillator, space rotor, non-degenerate stationary perturbation theory