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

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(nu, J) from the same effective internuclear potential. The IEC term value is defined by E-beta(IEC)(upsilon,J) E-beta(cal)(upsilon,J) + [E-alpha(exp)(upsilon,J)-E-alpha(cal)(upsilon,J)], where alpha and beta indicate isotopic molecules with reduced masses mu(alpha) and mu(beta) respectively. This approach is of special use for mu(alpha)approximate to mu(beta). 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 (LiH)-Li-6 and the (1,0)-(5,4) bands of (LiD)-Li-6 ground state, the uncertainties for most of them are estimated to be 0.0015-0.0020 cm (-1).