Many body perturbation theory in conjunction with the screening method has been applied to calculate radiative transition energies of highly charged ions. In the formulas obtained the energy values are averaged over LSJ as a function of the number of electrons distributed in up to 27 subshells taking relativistic energy shifts into account. The introduction of approximate screening parameters for nonrelativistic and relativistic parts of the energy allows us to limit our calculation to first order interelectron interaction only. The derived formulas have been proven to be very useful calculating X-ray spectra of Xeq+ (q = 44−48) ions interacting with the Cu surface. Comparison is made with other methods such as Hartree-Fock-Pauli (HFP), and relativistic model potential. Computational problems introducing different screening constants and asymptotic limits as well as contributions of the neglected second order interaction are discussed.
Nuclear quadrupole resonance (NQR) is a newly developed branch of radio frequency (RF) spectroscopic technique, allowing the detection of many substances containing quadrupole nuclei, such as14N and35Cl, widely existing in explosives and narcotics respectively. In this paper, we focus on the research of its detection mechanism for14N in urea and thiourea. Based on the Density Functional Theory (DFT), employing Beckes three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional (B3LYP), with 6-311++G(d,p) basis set, we have obtained the quantum chemical calculations by using Gaussian 09. Furthermore, experimental results and some discussions related are also presented. At last, we find that the absolute values of relative errors of NQR frequencies are all less than 2%, which indicates that this study is reasonable.
An analytical formula has been proposed to predict the high-lying spectral lines of rovibrational transitions for diatomic systems by Sun et al. who used multiple spectral difference method. This study improves the formula based on their previous work by adding a higher order spectral term Hv. Applications of this new formula to the AuO molecule shows that the accuracy of the P-branch rovibrational transition lines is about one order of magnitude better than the results obtained using the previous formula, and that the contributions of the small quantity Hv to the high-lying rovibrational energies and the transitional lines are shown to be important.
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