High-level Configuration Interaction Research Articles

Study of electronic structure and optical transition properties of low-lying excited states of AuB molecules based on configuration interaction method

High-level configuration interaction method including the spin-orbit coupling is used to investigate the low-lying excited electronic states of AuB that is not reported experimentally. The electronic structure in our work is preformed through the three steps stated below. First of all, Hartree-Fock method is performed to compute the singlet-configuration wavefunction as the initial guess. Next, we generate a multi-reference wavefunction by using the state-averaged complete active space self-consistent field (SACASSCF). Finally, the wavefunctions from CASSCF are utilized as reference, the exact energy point values are calculated by the explicitly correlated dynamic multi-reference configuration interaction method (MRCI). The Davidson correction (+Q) is put forward to solve the size-consistence problem caused by the MRCI method. To ensure the accuracy, the spin-orbit effect and correlation for inner shell electrons and valence shell electrons are considered in our calculation. The potential energy curves of 12 Λ-S electronic states are obtained. According to the explicit potential energy curves, we calculate the spectroscopic constants through solving radial Schrödinger equation numerically. We analyze the influence of electronic state configuration on the dipole moment by using the variation of dipole moment with nuclear distance. The spin-orbit matrix elements for parts of low-lying exciting states are computed, and the relation between spin-orbit coupling and predissociation is discussed. The predissociation is analyzed by using the obtained spin-orbit matrix elements of the 4 Λ-S states which spilt into 12 Ω states. It indicates that due to the absence of the intersections between the curves of spin-orbit matrix elements related with the 4 low-lying Λ-S states, the predissociation for these low-lying exciting states will not occur. Finally, the properties of optical transition between the ground Ω state <inline-formula><tex-math id="M3">\begin{document}$ {\rm A}^{1}{{{\Pi}}}_{1} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231347_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231347_M3.png"/></alternatives></inline-formula> and first excited Ω state <inline-formula><tex-math id="M4">\begin{document}$ {{\mathrm{X}}}^{1}{{{\Sigma }}}_{{0}^{+}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231347_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231347_M4.png"/></alternatives></inline-formula> are discussed in laser-cooling filed by analyzing the Franck-Condon factors and radiative lifetime. And the transition dipole moment is also calculated. But our results reveal that the AuB is not an ideal candidate for laser-cooling. In conclusion, this work is helpful in deepening the understanding of AuB, especially the structures of electronic states, interaction between excited states, and optical transition properties. All the data presented in this paper are openly available at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.doi.org/10.57760/sciencedb.j00213.00009">https://www.doi.org/10.57760/sciencedb.j00213.00009</ext-link>.

MRCI+Q study on the electronic structure and spectroscopy of the low-lying electronic states of HgBr including spin-orbit coupling

Due to attractive candidate for the laser application and searching for the permanent electric dipole moment of the electron (eEDM), mercury bromide (HgBr) is of much interest to researchers. However, detailed information of the electronic structure of HgBr is still lacking, especially for spin-orbit interactions in excited states. In this work, high-level configuration interaction calculations of low-lying states correlating to the lowest two dissociation limits Hg(1S) + Br(2P) and Hg(3P) + Br(2P) of HgBr are carried out. In order to ensure good accuracy, the Davidson correction and spin-orbit coupling (SOC) effect are all taken into consideration in our computations. The potential energy curves (PECs) of 14 Λ-S states and 30 Ω states are determined. Based on the PECs, the spectroscopic constants of the bound states are obtained, most of which have not been reported in previous studies. The calculated SOC integrals of 22Σ+-22Π indicate a strong spin-orbit interaction, which can explain the apparent perturbations between B2Σ+1/2 and C2Π1/2 found in the HgBr fluorescence excitation spectrum. Finally, to reveal more detail on transition properties of excited states, transition dipole moments of C2Π1/2-X2Σ+1/2, D2Π3/2-X2Σ+1/2, and B2Σ+1/2-X2Σ+1/2 transitions and radiative lifetimes of C2Π1/2, D2Π3/2, and B2Σ+1/2 are determined.

Laser cooling of the SiO+ molecular ion: A theoretical contribution

The feasibility of laser-cooling SiO+ molecular ion is studied by using ab initio methods. The electronic structures of 14 Λ-S states and 30 Ω states of SiO+ are computed by means of high-level configuration interaction method (including Davidson correction) with scalar relativistic correction. The calculated spectroscopic constants of bound states of SiO+ are in excellent agreement with available experimental results. The perturbation on vibrational levels of B2Σ+ is studied with the help of a spin-orbit coupling matrix elements which includes B2Σ+-14Σ−, B2Σ+-14Π, and B2Σ+-12Σ− interacting states pairs. The calculated Franck-Condon factors and branching ratio of the B2Σ+-X2Σ+ transition are highly diagonal. The radiative lifetime of B2Σ+ state is evaluated to be 72 ns, which is sufficiently short for laser cooling. On the basis of the B2Σ+-X2Σ+ transition, we propose a possible laser cooling scheme by using two lasers with wavelengths around 400 nm.

Spin-orbit calculations on the ground and excited electronic states of CdBr molecule

High-level configuration interaction method is used to calculate the 14 low-lying electronic states of CdBr. The spin-orbit coupling (SOC) effects are also taken into account. The potential energy curves (PECs) of the 14 Λ-S states, as well as those of 30 Ω states originating from those Λ-S states are determined. The spectroscopic constants of bound states are fitted based on the computed PECs, which agree well with previously available measurements. The predissociation of C2Π(ν′ ≥ 1)→B2Σ+is analyzed with the help of the SOC matrix elements. Finally, the lifetimes of vibrational levels ν′ = 0–5 of C2Π and B2Σ+states are calculated.

Electronic structures and spectroscopic properties of CdI: MRCI+Q study including spin-orbit coupling

Cadmium iodide (CdI), which is a candidate for laser material in chemical lasing, has attracted considerable scientific interest. While the complete picture for electronic structure of CdI is still unclear, particularly for the interactions of excited states. In this paper, high-level configuration interaction method is applied to compute the low-lying electronic states of the lowest two dissociation limits (Cd(1S) + I(2P) and Cd(3P) + I(2P)). To ensure the accuracy, the Davidson correction, core-valence electronic correlations and spin-orbit coupling effects are also taken into account. The potential energy curves of the 14 Λ-S states and 30 Ω states obtained from those Λ-S states are calculated. On the basis of the computed potential energy curves, the spectroscopic constants of bound and quasibound states are determined, most of which have not been reported in existing studies. The calculated values of spin-orbit coupling matrix elements demonstrate that the B2Σ+1/2 state imposes a strong perturbation on ν′> 0 vibrational level of C2Π1/2, which can explain the weak spectral intensity of C2Π1/2-X2Σ+1/2 observed in previous experiment. The transition dipole moments as well as the lifetimes are evaluated to predict the transition properties of B2Σ+1/2, C2Π1/2 and 22Π3/2 states.

Theoretical study on the electronic structure and transition properties of excited state of ZnH molecule

The potential energy curves (PECs) associated with the lowest four dissociation limits, i.e., Zn(1Sg)+H(2Sg), Zn(3Pu)+H(2Sg), Zn+(2Sg)+H-(1Sg) and Zn(1Pu)+H(2Sg), are calculated by using a high-level configuration interaction method. The Davidson correction, scalar relativistic effect and spin-orbit coupling effect are taken into account in calculation. On the basis of our calculated PECs of -S and states, the spectroscopic constants including Te, e, ee, Be and Re are evaluated by numerical solution of one-dimensional Schrdinger equation. The computed spectroscopic constants are reasonably consistent with previous experimental results. The dipole moment curves of the 7 -S states are presented, and the influences of the variation of electronic configuration on the dipole moment and bonding property are discussed. The computational results reveal the ionic character of the C2+ state. The variation of -S component for state near the avoided crossing point is illuminated, which is used to explain the change of transition dipole moment (TDM) around the avoided crossing point. Based on the TDMs, Franck-Condon factors and the transition energies, the radiative lifetimes of v'=0-2 vibrational levels of (2)1/2, (3)1/2, (4)1/2 and (1)3/2 states are predicted, which accord well with the available experimental values.

A Precise Description of the Electronic Structures and Spin-Allowed Transition Properties of PF and Its Cation: All-Electron Configuration-Interaction Investigations Including Relativistic Effect**Supported by the National Natural Science Foundation of China under Grant No 11404180, the Natural Science Foundation of Heilongjiang Province under Grant Nos F201335, A2015010, and A2015011, and the Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province under Grant

The electronic structures of PF and PF+ are calculated with the high-level configuration interaction method. To improve the precision of calculations, the spin-orbit coupling effect, the scalar relativistic effect, and the Davidson correction(+Q) are also considered. The spectroscopic parameters of bound states are derived by the electronic structures of PF and PF+, which are in good accordance with the measurements. The transition dipole moments of spin-allowed transitions are evaluated, and the radiative lifetimes of several ΓA–S states of PF and PF+ are obtained.

Collective electronic excitations in clusters in the vicinity of metal surfaces

We study the collective excitations of metal clusters approaching a metal surface. Using a simple model for the frequency-dependent dielectric constant e(ω) and the multiple scattering method, we numerically investigate the shift in the plasmon resonance due to the coupling of the collective modes of the sphere with those of its mirror image. Results of the model calculation are verified by means of ab initio theory. As a prototype system we study Na9 + cluster on the Cu(100) surface. The representation of the solid surface by a cluster of several, typically 54 substrate atoms, is used in combination with a high level configuration interaction (CI) calculation.

Ag 3 Born–Oppenheimer potential hypersurfaces

The full Born–Oppenheimer potential energy hypersurfaces of the Ag3 system have been explored by the local spin-density scheme using an analytic potential. Our calculated physical properties, such as dissociation energies and barriers to isomerization, compare well with the available high-level configuration interaction calculations and experiments at the equilibrium geometry. Despite its simplicity, the analytic potential provides an excellent description of the neutral trimer system for silver and the other transition metals.

Theoretical investigation of the lowest singlet and triplet excited states in oligo(phenylene vinylene)s and oligothiophenes

By means of a high-level configuration interaction technique, we describe the nature of the lowest singlet and triplet excited states in oligo(phenylene vinylene)s and oligothiophenes. We first calculate the evolution with chain length of the singlet-singlet and triplet-triplet excitation energies, as well as that of the singlet-triplet energy difference. The theoretical results compare favorably with the available experimental data. We then investigate the geometry relaxation phenomena occurring in the lowest excited states of model oligomers. We found that the lowest triplet state is characterized by more pronounced and local lattice distortions than the singlet state, especially in the case of the phenylene vinylene oligomers.