Non-Born-Oppenheimer approximation-the correction of the vibration spectrum for a diatomic molecule

In many cases, Born-Oppenheimer(BO) approximation is inadequate, it should be improved. In order to improve the BO approximation, authors impose to the electronic and nuclear wave functions to have a well defined phase difference. It enables us to correct some unsatisfactory results in the BO description. The purpose of this thesis is to correct the nuclear results in the BO description. By perturbation theory, authors derived the expressions of the nuclear wave functions and infrared vibration energy levels for diatomic molecule in detail. It should be closer to the experimental observations that the infrared vibration spectrum of a diatomic molecule obtained by means of our results.