Prediction of P-branch emission spectral lines of NaF and ⁶³Cu³⁵Cl molecules

An analytical formula for predicting R-branch high-lying transition lines of BiLi molecule

A concise and convenient analytical formula without any spectral constant is derived from the conventional expression of R-branch transitional energies for calculating the R-branch high-lying rovibrational emission spectral lines of diatomic molecule. This is based on the thought of Sun's difference converging method (DCM) in 2011. This formula can correctly predict the high-lying transitional emission spectral lines only using 11 known experimental transition lines and a set of physical criteria when any spectral constants of the system are not available. Furthermore, a new method for analyzing the accuracy of prediction with the improved formula is proposed, which point out the core problem of the predicted spectrum and give a quantitative conclusion on the reliability of our work. In this work, the new method is applied to study the R-branch transitional emission spectra of the (0-0) band of the A₂0⁺ → X₁0⁺ and A₂0⁺ → X₂1 transition systems of BiLi molecule. A series of experimental and theoretical comparisons and discussions show that under the condition of lack of any spectral constants, our method can still use 11 known experimental transition spectral data to reproduce the R-branch emission spectral lines reliably including the high excited rovibrational transition spectral lines.

Studying the R-branch and the Q-branch emission spectral lines of diatomic molecules using improved analytical formula

The difference converging method (DCM) used to predict the R-branch and the Q-branch high-lying rotational lines for diatomic systems is improved in this study. The key analytical formulae of the DCM method are modified by adding a higher order spectral term Hυ, and adding a physical converging criterion to improve the accuracy of predictions. Applications of the improved DCM method to the R-branch of the TiF molecule and the Q-branch of the (193)IrN molecule show that the accuracy of the R-branch and the Q-branch rotational lines is about one order of magnitude better than the results obtained using the previous formulae, which demonstrate the necessity of the added small term Hυ and the physical converging criterion. The DCM results are also shown to be better than the extrapolated rotational lines using the least-squares method.