Studies On Vibrational And/or Rotational Spectra Of Some Isotopic Diatomic Molecules

Accurate molecular spectra for isotopologues of the same species are important to researches in molecular physics, chemical physics and some other fields. To obtain the accurate isotopic molecular spectra we need an accurate molecular hamitonian in general. However, it is not very easy to reach such an aim, since it is not easy to obtain the accurate potential theoretically from the equilibrium distance to dissociation range for a given molecular state.In the present work an isotopic error compensation (IEC) approach is adopted to study the accurate spectrum for some diatomic isotopic molecular states, include the X and A electronic states of LiH, the ground electronic states of ZnO, ZnS,SiSe,SiTe,BO, and AgH isotopic molecules. The IEC approach is proposed for isotopic diatomic molecules based on the theoretical analysis of the errors of the rovibrational terms from the same effective internuclear potential, from which the errors of the isotopic spectral terms of the same quantum state are nearly the same. Therefore the errors of a given molecular state can be used as the approximate errors of the corresponding isotopic molecular states to calculate the accurate IEC spectra for the isotopic molecules. A variational method is used to obtain such a potential.The results show that (i) the IEC approach can be used to study more accurate spectra for isotopic molecules even the effective trial potential is not very accurate; (ii) the IEC approach can be used to predict more accurate spectra for isotopic molecules than the semi-classical isotope relation does. Some new spectral transition positions are obtained from this IEC approach.