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Abstract: The entire 12 Λ–S states of CCl+ correlated to ground state atom C+ and Cl are calculated at scalar relativistic MRCI+Q/AV5Z level of theory. Spin–orbit interaction causes the 12 Λ–S states to split into 23 Ω states. The potential energy curves (PECs) of Λ–S and Ω states are depicted with the aid of the avoided crossing rule between the same symmetry. This is the first time that spin–orbit coupling (SOC) calculation has been carried out on CCl+. The spin–orbit coupling effect, leading to many avoided crossings, is found to be substantial for CCl+. The spectroscopic constants of the bound Λ–S and Ω states are determined, where a better agreement with experimental data is found. The predissociations for a3Π and A1Π induced by SOC are analyzed. Moreover, the transition properties, including transition dipole moments and Franck–Condon factors, are derived. Subsequently, the radiative lifetimes of transition a3Π0+–X1Σ+ 0+ and a3Π1–X1Σ+ 0+ are calculated. [Copyright &y& Elsevier]

• Total 34 Λ-S states of SbI are accurately characterized at the MRCI+Q level. • The SOC effect makes 34 Λ-S states split into 74 Ω states. • Transition mechanisms of a1Δ-X3Σ− and b1Σ+-X3Σ− are illustrated. • The SOC effect is indispensible for accurate spectroscopic determinations of SbI. In this work, all-electron ab initio calculations on the SbI molecule have been carried out with the multi-reference configuration interaction plus the Davidson correction (MRCI+Q) method. In the calculations, total 34 Λ-S states have been obtained for the first time. From calculated PECs, the derived spectroscopic constants well agree with available experimental values. It should be mentioned that A3Π is typically repulsive, which much differs from the cases of lighter analogs SbX(X=F, Cl, and Br). The molecule is expected to possess a strong spin-orbit coupling effect because both Sb and I atoms have a large atomic number (Z). Therefore, this effect is included by using the state interaction method. As a result, there are 74 Ω states generated from Λ-S states. For X3Σ−, the determined energy splitting of 980 cm−1 is in good agreement with the measured value of 965 cm−1. The adiabatic excitation energy T e of b1Σ+ is greatly improved after considering the SOC effect. Transition properties of SbI are evaluated. The obtained results demonstrate that SOC effects have a great impact on the transitions a1Δ-X3Σ− and b1Σ+-X3Σ−. Both transitions borrow transition dipole moments (TDMs) from spin-allowed Λ-S transitions. The radiative lifetimes of a1Δ and b1Σ+ are determined to be 2.28 ms and 96.84 μs, respectively. [ABSTRACT FROM AUTHOR]

Highlights • Total 34 Λ-S states of AsCl have been studied with the MRCI+Q method. • High-precision spectroscopic results are obtained from the calculated PECs. • The SOC effect makes 34 Λ-S states split into 74 Ω states. • The transition mechanism of a1Δ-X3Σ− and b1Σ+-X3Σ− has been detailedly analyzed. • The accurate lifetimes of a1Δ and b1Σ+ are determined. Abstract A manifold of electronic states for the AsCl radical are accurately characterized at the MRCI+Q level of theory. The potential energy curves (PECs) of 34 Λ-S states, correlated with three dissociation channels, have been constructed, and the spectroscopic constants of the bound Λ-S are determined. The calculated spectroscopic results well reproduce the measurement. A characteristic feature for AsCl is that the open-shell π2 configuration can give rise to the lowest three strongly bound states X3Σ−, a1Δ, and b1Σ+. The spin-orbit (SO) coupling is included using the state interacting method. The calculated SO matrix element indicates that strongly bound a1Δ and b1Σ+ states can be predissociated by A3Π. The SO coupling effect leads to total 74 Ω states. And the calculated energy splitting of X3Σ− amounts to 125 cm−1, in good agreement with the experimental value of 140 ± 8 cm−1. Both a1Δ and b1Σ+ have no SO coupling splitting, and their spectroscopic constants almost keep unchanged. Nevertheless, their dissociation energies D e are strongly decreased due to the avoided crossing. Transition mechanism of several important transitions for AsCl has been clearly expounded. Particularly, the nonzero transition dipole moments (TDMs) of transitions a1Δ-X3Σ− and b1Σ+-X3Σ− are borrowed from spin-allowed Λ-S transitions. Ultimately, the radiative lifetimes of a1Δ and b1Σ+ are determined to be 27.1 ms and 1.1 ms, respectively. [ABSTRACT FROM AUTHOR]

The entire 28 Λ-S electronic states correlated to four dissociation limits of the NTe molecule have been reliably characterized for the first time. The potential energy curves (PECs) and wavefunctions of these Λ-S states are calculated using the multi-reference configuration interaction plus Davidson correction (MRCI+Q) approach, with all-electron correlation-consistent basis sets at quadruple-zeta level. The spectroscopic constants of the bound Λ-S states are determined from the PECs, and the excellent agreement with previous work is derived. By analyzing the dipole moment, the polarity of the ground state for NTe is determined to be N δ− Te δ+ , which is contrary to the case of NO. The spin-orbit coupling (SOC) effect is included when the state interaction method is applied. The SOC effect is found to be substantial for the NTe molecule, which makes the lowest 10 Λ-S states split into 30 Ω states. The X 2 Π states split into two Ω states including X 2 Π 1/2 (X 1 1/2) and X 2 Π 3/2 (X 2 3/2), and the corresponding SOC splitting is computed to be 1975 cm −1 (0.245 eV). Analysis of Λ-S compositions for the Ω-state wavefunction indicates the strong interaction among the Λ-S states. Additionally, the transition properties of the Ω-state transitions 1/2(2)-X 1 1/2, 1/2(4)-X 1 1/2, 3/2(10)-X 2 3/2, and 5/2(1)-X 2 3/2 were predicted. These transitions are all mainly from the spin-forbidden Λ-S transitions, but their transition dipole moments arise from those of the spin-allowed Λ-S transitions via the SOC effect. Accordingly, these transitions have quite long radiative lifetimes that are at the microsecond (ms) level. [ABSTRACT FROM AUTHOR]

The entire 23 Λ-S states of the PCl + molecule have been studied by using the high-level relativistic MRCI+Q method with full-electron aug-cc-pCVQZ-DK basis set. The potential energy curves(PECs) and wavefunctions of the states have been calculated. From the PECs, the spectroscopic constants of the bound states are also determined, and the good agreements could be found with the experiments. The high density region of states exhibits many PECs' crossings, which lead to complicated interaction of the states. Here, the interactions arising from the dipolar interaction and spin-orbit coupling (SOC) effect have been discussed in detail. Under the influence of the SOC effect, the A 2 Π state is perturbed by the 1 4 Σ - state. Considering the SOC effect, total 45 Ω states are generated from the original 23 Λ-S states. The transition properties are also predicted, including the transition dipole moments, Franck-Condon factors, and radiative lifetimes. The lifetimes of the transitions A 2 Π 1/2 -X 2 Π 1/2 and A 2 Π 3/2 -X 2 Π 3/2 are determined to be 478.9 ns and 487.0 ns( v' =0), respectively. [ABSTRACT FROM AUTHOR]

• A new approach for accurately measuring the spectral emissivity was proposed. • An emissivity measurement apparatus with high accuracy was constructed. • The fluctuation of surrounding radiation is eliminated by the isothermal aperture. Accurately measuring the spectral emissivity is of significant importance in thermal radiation. In this study, an improved measurement method for determination of spectral emissivity via modulating the surrounding radiation is proposed. A proof-of-concept measuring apparatus is constructed, and the main component parts are described in detail. The temperature uniformity of the isothermal aperture is verified, and the impact of the temperature uniformity on the emissivity measurements is studied. The good linearity and long-term stability of the detector is evaluated to ensure the validity of the improved method. The potential reference materials (silicon carbide and Armco iron) were used to validate the reliability and the accuracy of the measurement apparatus. The excellent data consistency of both two reference materials with the literature data demonstrates the reliability of the improved method and the measurement apparatus. The performance of the measurement apparatus with and without the isothermal aperture is compared, and the necessity of the modulated surrounding radiation is validated. The calculated combined uncertainty for the SiC sample at 1073 K is better than 2.38 %. The superior performance of the emissivity measurement apparatus indicate that the improved method proposed in this work provides a new approach for accurately measuring the spectral emissivity. [ABSTRACT FROM AUTHOR]

• Total 34 Λ-S states of SbBr are accurately characterized at the MRCI+Q level. • The SOC effect makes 34 Λ-S states split into 74 Ω states. • Transition mechanisms of a1Δ-X3Σ− and b1Σ+-X3Σ− are illustrated. • The SOC effect is indispensible for accurate spectroscopic determinations of SbBr. In this work, we performed spin-orbit coupling (SOC) included MRCI+Q calculation on electronic states of SbBr. The SOC effect is treated by using the state interaction method in combination with the Breit-Pauli operator. Molecular orbitals are constructed with all-electron aug-cc-pwCVQZ-DK basis sets. Without SOC, total 34 Λ-S states of SbBr are obtained. It is found that the lowest three Λ-S states X3Σ−, a1Δ, and b1Σ+ are characterized by a common electron configuration (π2). All of them possess an especially deep potential well. Predissociations of a1Δ and b1Σ+ are illuminated with the aid of SO matrix elements. Under the influence of SOC, total 74 Ω states arise from Λ-S states. The energy splitting of X3Σ− is calculated to be 868 cm−1, which well reproduces the measurement of 873 cm−1. Particularly, SOC effects significantly improve the excitation energy (T e) of b1Σ+. The deviation is decreased from 1378 cm−1 to 233 cm−1. In addition, the SOC effect has a great effect on transition properties of SbBr. This effect is responsible for the phosphorescence of transitions a1Δ-X3Σ− and b1Σ+-X3Σ−, and the corresponding transition mechanism is elucidated. Finally, radiative lifetimes of a1Δ and b1Σ+ are determined at a millisecond level. [ABSTRACT FROM AUTHOR]

• Total 34 Λ-S states of SbCl are accurately characterized at the MRCI+Q level. • The SOC effect makes 34 Λ-S states split into 74 Ω states. • Transition mechanisms of a1Δ-X3Σ- and b1Σ+-X3Σ- are illustrated. • The SOC effect is indispensible for accurate spectroscopic determinations of SbCl. In this paper, all-electron relativistic MRCI+Q calculation has been carried out on electronic and spectroscopic properties of SbCl. In present calculation, total 34 Λ-S and 74 Ω have been reliably characterized for the first time. The lowest three Λ-S states X3Σ−, a1Δ, and b1Σ+ possess a rather deep potential well, and resulting spectroscopic constants are consistent with experiments. The spin-orbit coupling (SOC) effect is considered with the state interaction method, and then the accuracy of computation is further improved. The SOC induced predissociations of a1Δ and b1Σ+ are illuminated by using spin-orbit matrix elements. It is found that the SOC effect is substantial for SbCl. The effect gives rise to a more complicated structure of electronic states. Transition properties of SbCl are estimated. R -dependent transition dipole moments (TDMs) are obtained at the MRCI level. Both a1Δ-X3Σ− and b1Σ+-X3Σ− borrow TDMs from spin-allowed Λ-S transitions via SOC. The lifetimes of a1Δ and b1Σ+ are determined at a millisecond (ms) level. [ABSTRACT FROM AUTHOR]