The Investigation Of Potential Energy Functions And Spectroscopic Prorerties Of Three Diatomic Molecule Systerms

Molecular potential energy function (PEF) is one of the important fields in atomic and molecular physics and quantum chemistry. It gives one absolute description of molecular properties and, it can completely determine molecular energy, equilibrium geometry, force constants and spectroscopic parameters. At the same time, it is also the foundation to investigate atomic and molecular collision and chemical reaction. It is of special importance in the atom-cluster area.In this paper, the ab initio calculation points of CP(X~2Σ~+, A~2П, B~2Σ~+), CO(X~1Σ~+) and CO~+(X~2Σ~+), AsP(X~1Σ~+)electronic states are investigated by using the CASSCF/MRCI theory in combination with a series of correlation-consistent basis sets of Dunning and co-workers. The spectroscopic parameters, De, Re,ωe,ωeχe,αe and Be of the CP(X~2Σ~+, A~2П, B~2Σ~+), CO (X~1Σ~+) and CO~+(X~2Σ~+), AsP(X~1Σ~+)electronic states are computed by the MOLCAS program package combined with the ab initio calculation points of the three states. The results are compared with the other theoretical and experimental data, showing that the present results are more accurate, even better than the other theoretical data. At the same time, the ab initio calculation points are fitted to the Murrell-Sorbie (M-S) function which can be used to calculate the complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants when the rotational quantum number J is set to equal zero (J = 0). Comparisons between these molecular constants and other theoretical and experimental results show that the present results are more accurate.The first part introduce the background and significance of the present research. In the second part, some basic theory and the main method of data processing, such as, the potential energy function, Born-Oppenheimer Approximation, Quantum mechanics approach and some software tools. In the third part, the results of the CP radical. In the fourth part, the results of the AsP molecule. In the fifth part, the results of CO (X~1Σ~+) and CO~+(X~2Σ~+) electronic states.The main conclusion of the paper are derived in the sixth part.