An isotopic error compensation method for rovibrational spectra of isotopic diatomic molecules

Abstract

An isotopic error compensation (IEC) approach is presented to study the accurate rovibrational spectra for isotopic diatomic molecules based on the theoretical analysis of the errors of the rovibrational term values E ^cal(υ, J) from the same effective internuclear potential. The IEC term value is defined by , where α and β indicate isotopic molecules with reduced masses μ_α and μ_β respectively. This approach is of special use for μ_α  ≈ μ_β . The IEC approach is also an effective way to eliminate large systematic errors introduced from the effective potential and the errors introduced by some Born–Oppenheimer breakdown effects. The results show that the IEC approach can be used to predict more accurate spectra for isotopic molecules than the semi-classical isotope relation does. The predicted IEC spectra are influenced by the accuracies of the observed isotopic molecule spectra, as well as the effective potential for the isotopic molecules used to calculate the IEC spectra. Some new IEC spectra data are predicted for the (1,0)–(4,3) bands of ⁶LiH and the (1,0)–(5,4) bands of ⁶LiD ground state, the uncertainties for most of them are estimated to be 0.0015–0.0020 cm⁻¹.

Keywords:

• Isotope effect
• Diatomic molecule
• Molecular spectra
• LiH

Acknowledgements

Professor Ronger Zheng is greatly appreciated for her help in preparing the manuscript. This work is supported by the National Natural Science Foundation of China (Grant No. 10474068) and the foundation of Ocean University of China (Grant No. 1001-813268, 2007XYK004).