Shilin Hou

Studies on full vibrational spectra and dissociation energies of some diatomic molecular electronic states using algebraic approaches

An algebraic energy method (AEM) is suggested as an alternative theoretical approach to generate molecular dissociation energy D e s. The AEM is used to evaluate accurate full vibrational energy spectra {E υ} and D e in this study for 14 diatomic electronic states of Li2, Na2, Rb2, K2 and Sr2 molecules: the 11Π g , , 23Πg, 13Δg and 23Δg states of Li2; the , , 13Δg and 23Δgstates of Na2; the and states of K2; the and 11Πg states of Rb2 and the state of Sr2 molecule. Studies show that present vibrational energies in the full spectrum {E υ} are accurate, and the AEM D e have an accuracy better than one percent when they are compared with experimental dissociation energies. The AEM can generate reliable D e s for electronic states whose molecular dissociation energies may be difficult to obtain experimentally and/or theoretically.

Relationship between Dipole Moments and Harmonic Vibrational Frequencies in Diatomic Molecules

Electric dipole moments and harmonic vibrational frequencies are two of the most important molecular properties in many fields of chemistry and physics. With the aid of classical physics, an empirical relationship between them was obtained for diatomic molecules as μd = kq(2)/(ReμAωe(2))(1/2), where k is a constant and μd, q, Re, μA, and ωe are the dipole moment, atomic charge, equilibrium bond length, reduced mass, and equilibrium vibrational frequency, respectively. This relation also provides the atomic charge q as a function of molecular dipole moment. Comparisons with over 60 molecules were made to test this relationship. For typical ionic molecules such as the alkali halides, the predicted dipole moments are in good agreement with the observed data assuming the atomic charges are 1 e. For general polar molecules, the estimated atomic charges obtained from the electric dipole moments are in good agreement with ab initio results for natural bond orbital and/or Mulliken populations.

Studies on rotational spectra of the ground states of ZnO, ZnS, SiSe and SiTe isotopic molecules using an isotopic error compensation approach

Accurate rotational spectra of 28 isotopologues of the ground electronic states of ZnO, ZnS, SiSe and SiTe are studied using an effective isotopic error compensation (IEC) approach. More than 200 new rotational transition frequencies are predicted for 20 of the above isotopologues using high-precision experimental data of the relevant isotopologues. The results show that the IEC approach can produce far more accurate rotational transition frequencies than the semi-classical isotope relation if the Born–Oppenheimer breakdown correction coefficients are ignored.

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(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 μα and μβ respectively. This approach is of special use for μα  ≈ μβ . 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.