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There are only limited theoretical results published on the transition properties of the X1Σ+, A1Π, B1Σ+, C1Δ, D1Σ−, E1Δ, a3Π, b3Σ+, and c3Δ states of BeS, and even some of the states have no theoretical and experimental reports on the relevant aspects of these transitions. Therefore, we derived these transition properties in this study. The potential energy curves of X1Σ+, A1Π, B1Σ+, C1Δ, D1Σ−, E1Δ, a3Π, b3Σ+, c3Δ, d3Σ−, and e3Σ− states of the BeS molecule with their Ω states and the transition dipole moments between them were calculated by the complete active space self-consistent field method, followed by the internally contracted multireference configuration interaction method. For the accurate computation of the transition properties, scalar relativistic corrections and core–valence correlation were considered. The radiative lifetimes were approximately 10−6 s for the A1Π and b3Σ+ states, 10−7 s for the E1Δ state, 10−7–10−8 s for the C1Δ and D1Σ− states, and 10−8 s for the B1Σ+, c3Δ, and e3Σ− states. The transition properties of the seven Ω states generated by the X1Σ+, A1Π, B1Σ+, and a3Π electronic states, including several electric dipole-forbidden transitions were researched. In particular, the B1Σ+0+–X1Σ+0+, B1Σ+0+–A1Π1, and A1Π1–X1Σ+0+ systems have strong transitions. In this paper, the radiative lifetimes of A1Π1, B1Σ+0+, a3Π0−, a3Π0+, and a3Π1 electronic states were also computed. For the A1Π1, B1Σ+0+, and a3Π1 states, the distribution of the radiation lifetime with the rotational angular momentum quantum number J at 0 ≤ υ ≤ 15 and J ≤ 70 was evaluated. It is expected that the outcome of the calculations in this paper can contribute some meaningful guidelines for conducting further theoretical and experimental investigations. [ABSTRACT FROM AUTHOR]

We have investigated, in a previous work, the transition dipole moments (TDM) of the 13 1Σ+ states of the (SrK)+ molecular ion by using the ab initio method based on the pseudo-potential approach. The radiative lifetimes for all vibrational levels of A and C1Σ+ have been calculated by using such transition dipole moments curves. We have included the bound-free emissions probabilities further to the bound–bound transitions. The bound-free emissions probabilities have been determined exactly, using the Franck–Condon approach, and then included in the total radiative lifetime. An important change has been observed for the higher excited vibrational levels in these lifetimes when the approximate evaluation breaks down. For the first time, the radiative lifetimes associated with the Aand C1Σ+ excited state have been studied here. [ABSTRACT FROM AUTHOR]

• Spectroscopic theoretical studies of RbS diatomic molecule. • Potential energy and dipole moments curves of RbS in its electronic ground and exited states. • Spin-orbit corrected potentials. • Franck–Condon factors and lifetime computations. • RbS is a good laser cooling molecular system candidate. We investigated the nineteen first electronic states of the RbS diatomic using post Hartree-Fock configuration interaction methods at the internally contracted multi-reference configuration interaction (MRCI+(Q)) level. We thus mapped their respective potential energy curves with and without considering spin-orbit effects. After nuclear motion treatments, we derived their equilibrium distances, rotational and vibrational constants, and dissociation and electronic excitation energies. Moreover, an evaluation of the dipole moments of RbS was conducted, which in turn were used to evaluate the radiative lifetimes of the vibrational levels of RbS (X2П and A2Σ+) states. Computations show that spin-orbit interactions are important and cannot be omitted. Afterwards, and utilizing the sum rule approximation and the Franck–Condon factors, we computed both the bound-bound contributions and the bound-free terms. Our findings suggest that RbS exhibits intriguing characteristics suitable for laser cooling experiments. In sum, this work contributes to the understanding in-depth of the spectroscopy of RbS and predicts its use as a promising molecular system for laser cooling applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Potential energy curves. • Molecular spectroscopic constants. • Radiative properties. • Optical cycles. • Transport properties. The KFr diatomic molecule represents a promising candidate for photoassociation and indirect laser cooling. It has not yet been investigated experimentally and remains the only representative of the family of alkali-metal diatomics, which is scarcely researched theoretically. The potential energy curves of the states belonging to the three lowest dissociation limits of the KFr molecule are calculated using the Fock-space relativistic coupled cluster theory for the first time. Properties and parameters, such as electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, sequences of vibrational energies, harmonic vibrational frequencies, Franck–Condon factors, and radiative lifetimes (including bound and free transitions), are predicted. We analyzed and evaluated the probabilities of the two-step schemes (optical cycles) for the transfer process of the KFr molecules from excited vibronic states to the ground vibronic state. The transport properties (diffusion, viscosity, and thermal conductivity coefficients) of two-component dilute gas media of potassium and francium atoms as functions of the translation temperature up to 3000 K are also calculated. The data obtained would be useful for laser cooling and spectral experiments with KFr molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon monosulfide was detected in outer space by rovibrational spectroscopy of the X 1Σ+ state and A 1Π – X 1Σ+ system. This work calculated the potential energy curves and dipole moment functions of the X 1Σ+0+ and A 1Π1 states, and computed the transition dipole moments between the two states employing the CASSCF method, followed by the valence icMRCI approach. Core-valence correlation and scalar relativistic corrections were included. The extrapolation of potential energies to the complete basis set limit was performed. The spin-orbit coupling effect was included. The Einstein A coefficients, band origins, and oscillator strengths were calculated for the rovibrational transitions when J ≤ 150. The rovibrational transitions of the X 1Σ+0+ and A 1Π1 states became very weak when Δυ ≥ 6. The Einstein A coefficients of vibronic emissions of the A 1Π1 – X 1Σ+0+ system were large, indicating that the emissions were able to be measured easily through spectroscopy. Several rovibrational transitions of the A 1Π1 – X 1Σ+0+ system were analysed in detail. The distribution of radiative lifetime varying as rotational quantum number was calculated. The results obtained in this work agree well with the available experimental values. [ABSTRACT FROM AUTHOR]

• Fock-space relativistic coupled cluster calculations. • Potential energy surfaces. • Molecular spectroscopic constants. • Radiative properties. • Laser cooling scheme. Herein, we present the state-of-the-art ab initio studies of the lower states of radium monohydroxide RaOH radical and its deuterated RaOD isotopologue. The potential energy surfaces of the ground and five low-lying excited states are calculated using the Fock-space relativistic coupled cluster method. The vibrational energy levels and all the fundamental frequencies are calculated for the first time using the potential energy surfaces and taking into account the interaction of the modes. Spectroscopic parameters such as electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, Franck–Condon factors, and radiative lifetimes are predicted. The probable vibrational laser cooling schemes are also proposed. [Display omitted] [ABSTRACT FROM AUTHOR]

• Transition dipole moments between different Λ-S states for CP are calculated. • Radiative transition probabilities for nineteen dipole-allowed transitions are discussed. • The spectral range for each band system is determined. • Rotationless radiative lifetimes of vibrational levels for some states are evaluated. The state-of-the-art ab initio -based valence internally contracted multireference configuration-interaction (icMRCI) method, including the Davidson correction, core-valence correction and scalar relativistic correction and the basis-set extrapolation, is used to calculate the potential energy curves (PECs) of the X2Σ+, B2Σ+, A2Π, 12Σ−, 12Δ, 22Δ, 22Σ−, 14Σ+, 24Σ+, 14Π, 14Δ, 14Σ−, 24Δ, 24Σ− 16Σ+ and 26Σ+ electronic states for CP radical. We also calculate the transition dipole moments (TDMs), Einstein coefficients and Franck-Condon factors for nineteen dipole allowed transitions between these sixteen states. The PECs are used to fit spectroscopic parameters, which are in excellent agreement with previous experimental and theoretical ones. The computed Franck-Condon factors also agree quite well with accurate semi-empirical results for the A2Π-X2Σ+ and B2Σ+-X2Σ+ systems. Such good agreement implies that the results are accurate enough to assist identification of the spectra from astrophysical sources. Large amounts of energy levels and transition data of high accuracy are provided in this work for CP radical of astrophysical interest, where experimental data are still scarce. [ABSTRACT FROM AUTHOR]

Abstract The ab initio quasirelativistic approach developed specifically for the calculation of spectral parameters of highly charged ions was used to derive transition data for the Nb-like tungsten ion W33+. The configuration interaction method was applied to include electron correlation effects. The relativistic effects were taken into account in the Breit–Pauli approximation. The level energies, radiative lifetimes τ , Landé g -factors were determined for the ground configuration 4p64d5 and two excited configurations 4p54d6 and 4p64d44f. The radiative transition wavelengths λ and emission transition probabilities A for the electric dipole, electric quadrupole, electric octupole, magnetic dipole, and magnetic quadrupole transitions among the levels of these configurations were produced. The uncertainties of computed spectroscopic parameters were evaluated. [ABSTRACT FROM AUTHOR]

Potential energy curves (PECs) of six electronic states ( X 2 Π , a 4 Σ - , A 2 Δ , B 2 Σ - , C 2 Σ + , and D 2 Σ + ) are calculated based on multi-reference configuration interaction plus Davidson corrections (MRCI + Q), and the spin–orbit coupling (SOC) effects are considered at the MRCI + Q level. By solving the radical Schrödinger equation, the spectroscopic constants of these states are obtained, which agree well with the experimental results. The SOC effects have little influence on spectroscopic constants. The permanent dipole moments (PDMs) and transition dipole moments (TDMs) of SiH molecule are also calculated with the same method. Highly diagonally distributed Franck-Condon factors (FCFs) are determined for the transitions X 2 Π ↔ A 2 Δ ( f 00  = 0.9858) and X 2 Π ↔ C 2 Σ + ( f 00  = 0.9676). Furthermore, the suitable radiative lifetimes τ of the A 2 Δ and C 2 Σ + states are 3.4625 × 10 −7  s and 1.6462 × 10 −7  s, which are evaluated for rapid laser cooling. Schemes to laser cooling SiH molecule are designed, and the proposed laser cooling drives for the transition X 2 Π ( ν ″ ) ↔ A 2 Δ ( ν ′ ) and X 2 Π ( ν ″ ) ↔ C 2 Σ + ( ν ′ ) both use three wavelengths. Main pump laser λ 00 for the two transitions are 401.31 and 319.64 nm. These results not only prove the feasibility of laser cooling SiH, but also provide a microkelvin cool temperature for this molecule. [ABSTRACT FROM AUTHOR]

A manifold of electronic states of ScS was investigated with special emphasis on the low-lying states X 2 Σ + , A´ 2 Δ, A 2 Π, and B 2 Σ + . For all states, potential energy curves were constructed covering internuclear distances from the equilibrium region through the dissociation limit. For the above states, besides providing the most accurate set of theoretical spectroscopic parameters to date, we have also computed dipole moment functions, transitions dipole moment functions, the associated radiative transition probabilities, and radiative lifetimes. For the states known experimentally, X 2 Σ + , A 2 Π, and B 2 Σ + , our results significantly expand our present knowledge of the energetic profile of these states thus providing a new perspective for understanding the limited spectral data for this species known so far. For the new state, A´ 2 Δ, yet unobserved experimentally, our results are sufficiently reliable and accurate to guide spectroscopists on further studies of this species. [ABSTRACT FROM AUTHOR]

The potential energy curves and transition dipole moments of 1 2 Σ + and 1 2 Π states of GaH + and InH + cations are performed by employing ab initio calculations. Based on the potential energy curves, the rotational and vibrational energy levels of the two states are obtained by solving the Schrödinger equation of nuclear movement. The spectroscopic parameters are deduced with the obtained rovibrational energy levels. The spin-orbit coupling effect of the 2 Π states for both the GaH + and InH + cations are also calculated. The feasibility of laser cooling of GaH + and InH + cations are examined by using the results of the electronic and spectroscopic properties. The highly diagonal Franck-Condon factors and appropriate radiative lifetimes are determined by using the potential energy curves and transition dipole moments for the 2 Π 1/2, 3/2 ↔ 1 2 Σ + transitions. The results indicate that the 2 Π 1/2, 3/2 ↔ 1 2 Σ + transitions of both GaH + and InH + cations are appropriate for the close cycle transition of laser cooling. The optical scheme of the laser cooling is constructed for the GaH + and InH + cations. [ABSTRACT FROM AUTHOR]

The potential energy curves and transition dipole moments of 1 2 Σ + , 2 2 Σ + , 1 2 Π and 2 2 Π states of NH + cation and NH − anion are calculated by using multi-reference configuration interaction method and large all-electron basis sets. Based on the obtained potential energy curves, the rotational and vibrational energy levels of the states are obtained by solving the Schrödinger equation of nuclear movement. The calculated spectroscopic parameters for NH + cation and NH − anion are in good agreement with available theoretical and experimental results. The spin orbit coupling effect of the 2 Π states for both NH + cation and NH − anion are calculated. The feasibility of laser cooling of the two molecules is examined by using the results of the molecular structure and spectroscopy. The highly diagonal Franck-Condon factors for the 1 2 Π (v″ = 0) ↔ 1 2 Σ + (v′ = 0) transition of NH + and NH − are 0.821 and 0.999, while the radiative lifetimes of the 1 2 Σ + (v′ = 0) state for the two molecules are 384 ns and 52.4 ns, respectively. The results indicate that NH + cation and NH − anion are good candidate molecules for laser cooling. The cooling scheme via Sisyphus process for the NH + cation and NH − anion are proposed in the paper. The laser wavelengths for the close cycles of the absorption and radiation are also determined. Unfortunately, the potential energy curve of the ground state of the neutral NH molecule shows that the auto-detachment of NH − anion is possible, implying the optical scheme of laser cooling for NH − anion is not easy to achieve in the experiment although it has larger Franck-Condon factor. [ABSTRACT FROM AUTHOR]

Optical dipole moment is the key parameter of optical transitions, as it directly determines the strength of light-matter interaction such as intrinsic radiative lifetime. However, experimental determination of these fundamental properties of excitons in monolayer WSe2 is largely limited, because the commonly used measurement, such as (time-resolved) photoluminescence, is inherently difficult to probe the intrinsic properties. For example, dark states below bright exciton can change the photoluminescence emission rate by orders of magnitude and gives an 'effective' radiative lifetime distinctive from the intrinsic one. On the other hand, such 'effective' radiative lifetime becomes important itself because it describes how dark states affect exciton dynamics. Unfortunately, the 'effective' radiative lifetime in monolayer WSe2 is also not determined as it requires photoluminescence measurement with resonant excitation, which is technically difficult. These difficulties are overcome here to obtain both the 'intrinsic' and 'effective' radiative lifetime experimentally. A framework is developed to determine the dipole moment and 'intrinsic' radiative lifetime of delocalized excitons in monolayer WSe2 from the absorption measurements. In addition, the 'effective' radiative lifetime in WSe2 is obtained through time-resolved photoluminescence and absolute quantum-yield measurement at resonant excitation. These results provide helpful information for fundamental understanding of exciton light-matter interaction in WSe2. [ABSTRACT FROM AUTHOR]

Optical dipole moment is the key parameter of optical transitions, as it directly determines the strength of light-matter interaction such as intrinsic radiative lifetime. However, experimental determination of these fundamental properties of excitons in monolayer WSe2 is largely limited, because the commonly used measurement, such as (time-resolved) photoluminescence, is inherently difficult to probe the intrinsic properties. For example, dark states below bright exciton can change the photoluminescence emission rate by orders of magnitude and gives an 'effective' radiative lifetime distinctive from the intrinsic one. On the other hand, such 'effective' radiative lifetime becomes important itself because it describes how dark states affect exciton dynamics. Unfortunately, the 'effective' radiative lifetime in monolayer WSe2 is also not determined as it requires photoluminescence measurement with resonant excitation, which is technically difficult. These difficulties are overcome here to obtain both the 'intrinsic' and 'effective' radiative lifetime experimentally. A framework is developed to determine the dipole moment and 'intrinsic' radiative lifetime of delocalized excitons in monolayer WSe2 from the absorption measurements. In addition, the 'effective' radiative lifetime in WSe2 is obtained through time-resolved photoluminescence and absolute quantum-yield measurement at resonant excitation. These results provide helpful information for fundamental understanding of exciton light-matter interaction in WSe2. [ABSTRACT FROM AUTHOR]

• Fock-space relativistic coupled cluster calculations • Potential energy curves • Molecular spectroscopic constants • Radiative properties • Optical cycles The LiFr diatomic represents a promising candidate for indirect laser cooling that has not yet been investigated not theoretically or experimentally. The potential energy curves of the ground and low-lying excited states of the LiFr heteronuclear alkali metal dimer are calculated using the Fock-space relativistic coupled cluster theory for the first time. A number of properties such as the electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, sequences of vibrational energies, harmonic vibrational frequencies, Franck–Condon factors, and radiative lifetimes (including bound and free transitions) are predicted. The probabilities of the two-step schemes (optical cycles) for the transfer process of the LiFr molecules from high excited vibrational states to the ground vibronic state are also predicted. The data obtained would be useful for laser cooling and spectral experiments with LiFr molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

A wide adiabatic study has been performed for numerous electronic states of CaLi+molecular ion. The adiabatic potential energy curves and their spectroscopic constants (Re, De, ωeand Te) have been calculated using anabinitioapproach including a nonempirical pseudo-potential for the Ca and Li cores with the core polarisation potentials operator through full configuration interaction (FCI). Thereafter, the energies of vibrational levels and their spacing for all these states have been reported. In addition, the electric dipole moment curves have been investigated for the (1-19) Σ, (1-12) Π and (1-8) Δ electric states. Moreover it lets us check the extreme transition dipole moments (TDM). These behaviours of TDM are more accustomed to estimate the radiative lifetimes for all vibrational levels in 21Σ+and 31Σ+states. Also, the bound-bound and the bound-free contribution have been calculated precisely and by employing a Franck–Condon (FC) approximation. [ABSTRACT FROM PUBLISHER]

Ab initio calculations on potential energy curves (PECs), spectroscopic constants, transition dipole moments, radiative transition probabilities and lifetimes for the ground state (X 2 Σ + ) and the first excited state (A 2 Π) of MgX (X = F, Cl, Br, I) molecules are determined by high-level internally contracted multi-reference configuration interaction (ic-MRCI) method. In order to improve the calculation, the Davidson modification (+Q) and scalar relativistic correction are included. The present results show that most of spectroscopic constants are in accordance with the measurements, the equilibrium internuclear distance R e increases while the other spectroscopic constants reduce along with the increasing of the atomic number of the halogen from F to I. Diagonal vibrational transitions are found to be dominant for the A 2 Π→X 2 Σ + system of MgX molecules. The corresponding radiative lifetimes of ν ′ = 0 are computed to be 7.24, 9.98, 18.94 and 22.72 ns for MgF, MgCl, MgBr, and MgI, respectively. The calculated result of MgF molecule is in good agreement with the recent theoretical result of 7.16 ns, with a small relative error percent of 1.11%. [ABSTRACT FROM AUTHOR]

• Fock-space relativistic coupled cluster calculations. • Potential energy curves. • Molecular spectroscopic constants. • Radiative properties. • Laser cooling scheme. The main focus of this study is the radium monoiodide RaI molecule, which is a promising candidate for direct laser cooling. To support this statement we calculated the potential energy curves of the ground and five low-lying excited states using the Fock-space relativistic coupled cluster theory. Calculations of spectroscopic properties including electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, vibrational energies and harmonic vibrational frequencies, Frank–Condon factors and radiative lifetimes were also performed. Based on the results we conclude that RaI molecule can be used for direct laser cooling and propose the probable laser cooling scheme. This work continues the series of research of radium monohalides and includes the comparison of results with previously studied RaCl, RaF and RaBr molecules. It can provide an understanding of trends in spectroscopic and radiative properties of this alkaline earth metal monohalides series. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The lowest-lying electronic states of LiAs are studied by the CASSCF/MRCI/ aV5Z(-PP) ab initio approach. We report full potential energy curves (PECs) as well as the associated spectroscopic constants, and dipole moment functions for the bound states. The transition dipole moment and transition probabilities associated with A3Π–X3Σ− band system are discussed and the radiative lifetimes of various vibrational levels of the A3Π state are also estimated. Spin–orbit effects were also taken into account leading to some distinctive properties in the PEC’s, mainly because of the presence of repulsive state a 5Σ− that also correlates with the first channel. Similarities and differences with the systems, AsH, LiN and LiP are also discussed. [Copyright &y& Elsevier]

The structure and spectroscopic properties of the ground and the lowest excited electronic states of the alkali hydride cation NaH+ have been investigated using an ab initio approach. In this approach, a nonempirical pseudopotential for the Na+ core has been used and a core-core and a core-valence correlation corrections have been added. The adiabatic potential energy curves and the molecular spectroscopic constants for numerous electronic states of 2Σ+, 2Π, and 2Δ symmetries, dissociating up to Na (4 d) + H+ and Na+ + H (3 d), have been calculated. As no experimental data are available, we discuss our results by comparing with the available theoretical calculations. A satisfying agreement has been found for the ground state with previous works. However, a clear disagreement between this study and the model potential work of Magnier (Magnier, J. Phys. Chem. A 2005, 109, 5411) has been observed for several excited states. Numerous avoided crossings between electronic states of 2Σ+ and 2Π symmetries have been found and analysed. They are related to the interaction between the potential energy curves and to the charge transfer process between the two ionic systems Na+H and NaH+. Furthermore, we provide an extensive set of data concerning the transition dipole moments from X2Σ+ and the 22Σ+ states to higher excited states of 2Σ+ and 2Π symmetries. Finally, the adiabatic potential energy curves of the ground (X2Σ+) and the first (22Σ+) excited states and the transition dipole moments between these states are used to evaluate the radiative lifetimes for the vibrational levels of the 22∑+ state for the first time. In addition to the bound-bound contribution, the bound-free term has been evaluated and added to the total radiative lifetime. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We calculate multireference configuration-interaction wavefunctions and the potential-energy curves for the $ {B^3}\Sigma_u^{-} $ and $ {X^3}\Sigma_g^{-} $ states of the collision-free S molecule and the T-shape collision complex S-He using cc-pVQZ basis sets. We obtain the transition dipole moments of the $ {{\text{S}}_2}\left( {{B^3}\Sigma_u^{-} \to {X^3}\Sigma_g^{-} } \right) $ and the Franck-Condon factors between the vibrational levels of this two states. We evaluate the radiative lifetimes of $ {{\text{S}}_2}\left( {{B^3}\Sigma_u^{-} \left( {{\upsilon^{\prime}} = 0 - 9} \right)} \right) $ levels of the collision complex and the collision-free molecule and compare them with the experiments. The collision provides little change in the radiative lifetimes of $ {{\text{S}}_2}\left( {{B^3}\Sigma_u^{-} \left( {{\upsilon^{\prime}} = 0 - 9} \right)} \right) $ according to the previous calculations. We obtain excellent agreement between the theoretical results and the experiments. The data calculated are very useful in the study of the microwave-driven high-pressure sulfur lamp and an S laser pumped by a transverse fast discharge. [ABSTRACT FROM AUTHOR]

[Display omitted] The influence of spin-orbit coupling on the cooling of NH molecular laser is investigated based on the ab initio theory. The potential energy curves (PECs) and spectral constants for four Λ - S states ( X 3 Σ - , a 1 Δ , b 1 Σ + and A 3 Π) and eight Ω states (X 3 Σ 0 + , 1 - , a 1 Δ 2 , b 1 Σ 0 + + and A 3 Π 0 - , 0 + , 1 , 2 ) of NH molecule are obtained by the multi-reference configuration interaction (MRCI) plus Davidson correction. The spectroscopic constants (R e , ω e , ω e χ e , B e , D e) are obtained by solving the one dimensional radial Schrödinger equation, and the results are almost the same as the previously reported data. In addition, the transition dipole moment, permanent dipole moment, Franck-Condon factors, and radiative lifetime of NH molecule are also acquired. Also, the effects of the intermediate state on the X 3 Σ 0 + - ↔ A 3 Π 1 , X 3 Σ 1 - ↔ A 3 Π 0 + and X 3 Σ 1 - ↔ A 3 Π 0 - transitions are considered. The feasible laser cooling schemes using a single laser are formulated. In the proposed cooling scheme, there wavelengths for the X 3 Σ 0 + - ↔ A 3 Π 1 are used, the main pump lasers are λ 00 = 335.74 nm. The feasible transition is based on this. It is found that spin-orbit coupling has a significant effect on potential energy curves, permanent dipole moments, transition dipole moments and vibration energy levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fock-space relativistic coupled cluster calculations. • Potential energy curves. • Molecular spectroscopic constants. • Radiative properties. • Laser cooling scheme. The potential energy curves of the ground and five low-lying excited terms of the RaF molecule are calculated using the Fock-space relativistic coupled theory. The electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, sequences of vibrational energies, harmonic vibrational frequencies, Franck–Condon factors, and radiative lifetimes are predicted. The calculated spectroscopic constants are in good agreement with the available theoretical and experimental data. The scheme for the direct laser cooling involving the first excited A 2П 1/2 state is proposed. The data obtained in this study suggests the A 2П 1/2 → X 2Σ+ channel in the RaF molecule is the almost ideal case for direct laser cooling. It is quite possible that the effective cooling scheme for the RaF molecule can be realized using only one pump laser. [ABSTRACT FROM AUTHOR]

• Fock-space relativistic coupled cluster calculations. • Potential energy curves. • Molecular spectroscopic constants. • Radiative properties. • Laser cooling scheme. The potential energy curves of the ground and five low-lying excited states of the RaBr molecule are calculated using the Fock-space relativistic coupled cluster theory for the first time. A number of properties such as the electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, sequences of vibrational energies, harmonic vibrational frequencies, Franck–Condon factors, and radiative lifetimes are predicted. The results of this study show that RaBr molecules can be used for the direct laser cooling. The comparison to the previous theoretical studies of the RaF and RaCl molecules is also provided. [Display omitted] [ABSTRACT FROM AUTHOR]

• b3Π – d3Δ transition is weak. • A1Π – X1Σ+ and E1Σ+ – X1Σ+ transitions are strong. • Lifetime is 4.3 – 9.8 ms for the a3Σ+ 1 state and 3.8 – 35.4 ms for a3Σ+ 0– state. • Lifetime is 117 – 380 μs for the b3Π 0+ state and 73 – 581 μs for the b3Π 1 state. • Lifetime is 107.6 – 120.5 ns for the A1Π state and 12.8 – 14.1 ns for the E1Σ+ state. The transition properties of the X1Σ+, C1Σ–, D1Δ, A1Π, E1Σ+, a3Σ+, d3Δ, and b3Π states of silicon monosulphide were investigated using the complete active space self-consistent field method, which was followed by the internally contracted multireference configuration interaction approach. The transition dipole moments were calculated for the dipole–allowed transitions between these singlet states and for all transitions between the X1Σ+, a3Σ+, d3Δ, and b3Π states. The radiative lifetimes of the first 16 vibrational levels were 107.6 – 120.5 ns for the A1Π state and 12.8 – 14.1 ns for the E1Σ+ state. Among these dipole–allowed transitions, the emissions from the A1Π – X1Σ+ and E1Σ+ – X1Σ+ systems were strong, whereas those from the b3Π – d3Δ system were weak. The radiative lifetimes of the first 16 levels were 4.3 – 9.8, 3.8 – 35.4, 2.2 – 7.9, and 11.9 – 14.5 ms for the a3Σ+ 1 , a3Σ+ 0– , d3Δ 1 , and d3Δ 2 states, respectively. These were 117 – 380, 73 – 581, and 137 – 586 μs for the b3Π 0+ , b3Π 1 , and b3Π 2 states, respectively. Among these forbidden transitions, the b3Π 0+ – X1Σ+ 0+ and b3Π 1 – X1Σ+ 0+ transitions were the strongest. The Franck–Condon factors, Einstein A coefficients, and band origins of all these spontaneous emissions were calculated. The transition properties were compared with the available experimental and theoretical results. The transition properties of the X1Σ+, C1Σ–, D1Δ, A1Π, E1Σ+, a3Σ+, d3Δ, and b3Π states of SiS are calculated; the TDMs of the dipole–allowed transitions between the singlet states are determined; and the TDMs of all transitions between the X1Σ+, a3Σ+, d3Δ, and b3Π states are computed. The radiative lifetimes of the first 16 vibrational levels are 107.6 – 120.5 ns for the A1Π state and 12.8 – 14.1 ns for the E1Σ+ state. These are 4.3 – 9.8, 3.8 – 35.4, 2.2 – 7.9, and 11.9 – 14.5 ms for the a3Σ+ 1 , a3Σ+ 0– , d3Δ 1 , and d3Δ 2 states, respectively. And these are 117 – 380, 73 – 581, and 137 – 586 μs for the b3Π 0+ , b3Π 1 , and b3Π 2 states, respectively. Among all dipole–allowed transitions, the A1Π – X1Σ+ and E1Σ+ – X1Σ+ transitions are strong, whereas the b3Π – d3Δ transition is weak. Among all forbidden transitions, the b3Π 0+ – X1Σ+ 0+ and b3Π 1 – X1Σ+ 0+ transitions are the strongest. [Display omitted] [ABSTRACT FROM AUTHOR]

• Lifetime is approximately 88.7 – 175.6 µs for the e2Σ+ 1/2 state. • d2Π 1/2 – a2Σ– 1/2 and d2Π 3/2 – a2Σ– 1/2 transitions are the strongest. • Lifetimes are 29.3 – 40.4 and 21.2 – 30.1 µs for the d2Π 1/2 and d2Π 3/2 states, respectively. • Lifetimes are 4.8 – 679.5 and 2.2 – 431 ms for the c2Π 1/2 and c2Π 3/2 states, respectively. • d2Π 3/2 – b2Δ 3/2 , 5/2 , c2Π 3/2 , e2Σ+ 1/2 – c2Π 1/2 , 3/2 , and d2Π 1/2 – b2Δ 3/2 , c2Π 1/2 transitions are strong. Detecting aluminum silicon can yield useful information concerning the depletion of silicon and aluminum and their recycling in astrophysical sources. In addition, such detection can be helpful for understanding gas–phase aluminum and silicon chemistry in the interstellar/circumstellar atmosphere. However, only a few transition properties of this radical have been reported. Therefore, the potential energy curves of several lowest–lying doublet states and the transition dipole moments between them were calculated using the icMRCI approach. Core–valence correlation correction, scalar relativistic correction, and spin–orbit coupling effect were included to improve the accuracy of transition properties. The radiative lifetimes of the first 16 levels were approximately 4.8 – 679.5 ms for the c2Π 1/2 state, 2.2 – 431 ms for the c2Π 3/2 state, 29.3 – 40.4 µs for the d2Π 1/2 state, 21.2 – 30.1 µs for the d2Π 3/2 state, and 88.7 – 175.6 µs for the e2Σ+ 1/2 state. The spontaneous emissions from the c2Π 1/2 and c2Π 3/2 states to the a2Σ– 1/2 , b2Δ 3/2 , and b2Δ 5/2 states and those from the e2Σ+ 1/2 state to the d2Π 1/2 and d2Π 3/2 states were located in the radio–frequency region. The d2Π 1/2 – a2Σ– 1/2 and d2Π 3/2 – a2Σ– 1/2 transitions were the strongest, followed by d2Π 1/2 – b2Δ 3/2 , d2Π 3/2 – b2Δ 3/2 , d2Π 3/2 – b2Δ 5/2 , d2Π 1/2 – c2Π 1/2 , d2Π 3/2 – c2Π 3/2 , e2Σ+ 1/2 – c2Π 1/2 , and e2Σ+ 1/2 – c2Π 3/2 transitions. The spontaneous emissions from these systems were located in the infrared region. The variation in the radiative lifetime of a level υ versus the rotational quantum number J was investigated for the d2Π 1/2 , d2Π 3/2 , and e2Σ+ 1/2 states. The radiative lifetimes of the first 16 vibrational levels were roughly 4.8 – 679.5 ms for the c2Π 1/2 state, 2.2 – 431 ms for the c2Π 3/2 state, 29.3 – 40.4 µs for the d2Π 1/2 state, 21.2 – 30.1 µs for the d2Π 3/2 state, and 88.7 – 175.6 µs for the e2Σ+ 1/2 state. The spontaneous emissions from the c2Π 1/2 and c2Π 3/2 states to the a2Σ– 1/2 , b2Δ 3/2 , and b2Δ 5/2 states and those from the e2Σ+ 1/2 state to the d2Π 1/2 and d2Π 3/2 states are distributed in the radio–frequency region. The emissions from the d2Π 1/2 – a2Σ– 1/2 and d2Π 3/2 – a2Σ– 1/2 systems are the strongest, followed by d2Π 1/2 – b2Δ 3/2 , d2Π 3/2 – b2Δ 3/2 , d2Π 3/2 – b2Δ 5/2 , d2Π 1/2 – c2Π 1/2 , d2Π 3/2 – c2Π 3/2 , e2Σ+ 1/2 – c2Π 1/2 , and e2Σ+ 1/2 – c2Π 3/2 transitions. The spontaneous emissions from these systems are located in the IR region. [Display omitted] [ABSTRACT FROM AUTHOR]

• Lifetime is 9 – 20 and 12 – 22 μs for the A2Π 1/2 and A2Π 3/2 states, respectively. • B2Σ+ 1/2 –A2Π 3/2 , B2Σ+ 1/2 –A2Π 1/2 and C2Π 3/2 –A2Π 1/2 transitions are strong. • C2Π 3/2 – X2Σ+ 1/2 , C2Π 1/2 – X2Σ+ 1/2 and C2Π 1/2 –A2Π 3/2 transitions are the strongest. • b4Δ 1/2 –X2Σ+ 1/2 , b4Δ 1/2 –A2Π 3/2 and b4Δ 1/2 –A2Π 1/2 forbidden transitions are the strongest. • Lifetimes are 361 – 553 and 298 – 513 ns for the C2Π 1/2 and C2Π 3/2 states, respectively. A number of experiments have been performed to measure the transition properties of the low–lying states of boron monosulfide; however, only a few theoretical results have been reported in the literature. Thus, the transition properties of several of the lowest–lying states are investigated herein. The potential energy curves of the Ω states generated from the X2Σ+, A2Π, B2Σ+, C2Π, a4Σ+, and b4Δ states and the transition dipole moments between them were calculated using icMRCI approach. The radiative lifetimes of the first 16 levels were of the order of 9 – 20, 12 – 22, and 1.3 – 6.5 μs for the A2Π 1/2 , A2Π 3/2 , and B2Σ+ 1/2 states, respectively; those were approximately 361 – 553 and 298 – 513 ns for the C2Π 1/2 and C2Π 3/2 states, respectively. The C2Π 3/2 – X2Σ+ 1/2 , C2Π 1/2 – X2Σ+ 1/2 , and C2Π 1/2 – A2Π 3/2 transitions were the strongest, followed by the B2Σ+ 1/2 – A2Π 3/2 , B2Σ+ 1/2 – A2Π 1/2 , and C2Π 3/2 – A2Π 1/2 transitions. The transitions from the a4Σ+ and b4Δ states to the X2Σ+ state were evaluated. The radiative lifetimes of the first 16 levels were of the order of 3.2 – 6.0, 8.9 – 17.3, and 61 – 7644 ms for the a4Σ+ 3/2 , a4Σ+ 1/2 , and b4Δ 5/2 , respectively; those were approximately 15 – 1430 and 7 – 1006 μs for the b4Δ 3/2 and b4Δ 1/2 states, respectively. Among these forbidden transitions, the emissions from the b4Δ 1/2 – X2Σ+ 1/2 , b4Δ 1/2 – A2Π 3/2 , b4Δ 1/2 – A2Π 1/2 , b4Δ 1/2 – X2Σ+ 1/2 , b4Δ 1/2 – A2Π 3/2 , and b4Δ 1/2 – A2Π 1/2 systems were strong. The distribution of the radiative lifetime at a level υ versus the rotational quantum number J was evaluated for the A2Π 1/2 , A2Π 3/2 , B2Σ+ 1/2 , C2Π 1/2 , and C2Π 3/2 states. The radiative lifetimes are 9 – 20, 12 – 22, and 1.3 – 6.5 μs for the A2Π 1/2 , A2Π 3/2 , and B2Σ+ 1/2 states, respectively; those were 361 – 553 and 298 – 513 ns for the C2Π 1/2 and C2Π 3/2 states, respectively; these are of the order 3.2 – 6.0, 8.9 – 17.3, and 61 – 7644 ms for the a4Σ+ 3/2 , a4Σ+ 1/2 , and b4Δ 5/2 , respectively; those were 15 – 1430 and 7 – 1006 μs for the b4Δ 3/2 and b4Δ 1/2 states, respectively. The C2Π 3/2 – X2Σ+ 1/2 , C2Π 1/2 – X2Σ+ 1/2 , and C2Π 1/2 – A2Π 3/2 transitions are strongest, followed by the B2Σ+ 1/2 – A2Π 3/2 , B2Σ+ 1/2 – A2Π 1/2 , and C2Π 3/2 – A2Π 1/2 transitions. The b4Δ 1/2 – X2Σ+ 1/2 transition is the strongest, followed by the b4Δ 1/2 – A2Π 3/2 and b4Δ 1/2 – A2Π 1/2 forbidden transitions. The strong emissions from the A2Π 3/2 – X2Σ+ 1/2 and A2Π 1/2 – X2Σ+ 1/2 systems are mainly in the visible region; only a small number are in the IR and UV regions. The strong emissions from the B2Σ+ 1/2 – X2Σ+ 1/2 , C2Π 1/2 – A2Π 3/2 , C2Π 1/2 – A2Π 1/2 , C2Π 3/2 – A2Π 3/2 , and C2Π 3/2 – A2Π 1/2 systems are located in the UV and visible region; those from the B2Σ+ 1/2 – A2Π 3/2 and B2Σ+ 1/2 – A2Π 1/2 transitions are in the visible region; those from the C2Π 3/2 – X2Σ+ 1/2 and C2Π 1/2 – X2Σ+ 1/2 systems are in the UV region; those from C2Π 3/2 – B2Σ+ 1/2 and C2Π 1/2 – B2Σ+ 1/2 systems are of IR light. [Display omitted] [ABSTRACT FROM AUTHOR]

• B2Σ+ 1/2 – X2Σ+ 1/2 transition is strong. • A2Π 1/2, 3/2 – X2Σ+ 1/2 and B2Σ+ 1/2 – A2Π 1/2, 3/2 transitions are strong. • Lifetimes are 10 μs for the A2Π 1/2, 3/2 states and 100 ns for the B2Σ+ 1/2 state. • Lifetimes are 10 and 10 – 100 ms for the a4Σ+ 1/2 and a4Σ+ 3/2 , respectively. • Lifetimes are 10, 0.1 – 1, and 10 ms for the b4Δ 1/2 , b4Δ 3/2 , and b4Δ 5/2 states, respectively. The potential energy curves of X 2Σ+, A 2Π, B 2Σ+, a 4Σ+, and b 4Δ states and their Ω states of CP were calculated using the icMRCI approach. The transition dipole moments between these states were computed. To improve the accuracy of the potential energy curves, core–valence correlation and scalar relativistic corrections were considered. The radiative lifetimes were approximately 10 μs for the A 2Π 3/2 and A 2Π 1/2 states and 100 ns for the B2Σ+ 1/2 state; those were approximately 10, 10 – 100, 10, 0.1 – 1, and 10 ms for the a 4Σ+ 1/2 , a 4Σ+ 3/2 , b 4Δ 1/2 , b 4Δ 3/2 , and b 4Δ 5/2 states, respectively. The spontaneous emissions from the B 2Σ+ 1/2 – X 2Σ+ 1/2 system were strong, followed by the A 2Π 3/2 – X 2Σ+ 1/2 , A 2Π 1/2 – X 2Σ+ 1/2 , B 2Σ+ 1/2 – A 2Π 3/2 , and B 2Σ+ 1/2 – A 2Π 1/2 transitions. The strong emissions from the A 2Π 3/2 – X 2Σ+ 1/2 and A 2Π 1/2 – X 2Σ+ 1/2 systems were in the infrared region; those from the B 2Σ+ 1/2 – X 2Σ+ 1/2 system were in the visible and ultraviolet regions; and those from the B 2Σ+ 1/2 – A 2Π 3/2 , and B 2Σ+ 1/2 – A 2Π 1/2 systems were of visible light. A simple comparison shows that the effect of the spin–orbit coupling on the radiative lifetimes of the A 2Π and B 2Σ+ states was significant. The radiative–lifetime distribution of each level υ versus the rotational quantum number J was evaluated for υ ≤ 15 and J ≤ 70.5. The PECs of the X2Σ+, A2Π, B2Σ+, a4Σ+, and b4Δ states and their Ω states of CP are calculated. The TDMs between these states are computed. The radiative lifetimes are of the order of 10 μs for the A2Π 3/2 and A2Π 1/2 states and 100 ns for the B2Σ+ 1/2 state. Those are of the order of 10, 10 – 100, 10, 0.1 – 1, and 10 ms for the a4Σ+ 1/2 , a4Σ+ 3/2 , b4Δ 1/2 , b4Δ 3/2 , and b4Δ 5/2 states, respectively. The SOC effect evidently increases the radiative lifetime of the A2Π state; however, it significantly decreases the radiative lifetime of the B2Σ+ state. The B2Σ+ 1/2 – X2Σ+ 1/2 transition is strong, followed by the A2Π 3/2 – X2Σ+ 1/2 , A2Π 1/2 – X2Σ+ 1/2 , B2Σ+ 1/2 – A2Π 3/2 , and B2Σ+ 1/2 – A2Π 1/2 transitions. The strong emissions from the A2Π 3/2 – X2Σ+ 1/2 and A2Π 1/2 – X2Σ+ 1/2 systems are in the IR region; those from the B2Σ+ 1/2 – X2Σ+ 1/2 system are in the visible and UV regions, and those from the B2Σ+ 1/2 – A2Π 3/2 , and B2Σ+ 1/2 – A2Π 1/2 systems are in the visible region. [Display omitted] [ABSTRACT FROM AUTHOR]

• A1Π – X1Σ+ transition is strong. • Almost all strong emissions are located in the UV region. • Radiative lifetime of all levels of the A 1Π state are 6.2–16.7 ns. • Radiative lifetime of a level υ gradually increases with J for all levels. • Most of the emissions are in the UV region. Only a few are in the visible region. The potential energy curves of the X1Σ+ and A1Π states of aluminum monochloride radical and the transition dipole moments between them were calculated using the icMRCI approach. Core–valence correlation and scalar relativistic corrections were applied. The extrapolation of the potential energies to the complete basis set limit was considered to improve the quality of the potential energy curves. In order to accurately calculate the rovibrational transition positions of the A1Π – X1Σ+ system, the experimental T e value of the A1Π state was used to improve the reliability of the ab initio results. The radiative lifetimes of all vibrational states of the A1Π state were calculated and compared with the available experimental and theoretical results. The variation of the radiative–lifetime distribution with the rotational quantum number was obtained. The rovibrational transition positions, Einstein A coefficients, oscillator strengths, and Franck–Condon factors of the P, Q, and R branches of the vibronic emissions of this system were calculated up to J = 150. The Einstein A coefficients were large for numerous vibronic bands, indicating that these transitions were easily measured via spectroscopy. A Comparison with available measurements shows that the transition properties reported herein are accurate. [ABSTRACT FROM AUTHOR]

• Reliable and accurate potential energy curves for Λ + S and Ω states of SrI. • Most complete characterization of the states to date. • Dipole and transition moments, Einstein A v´v´´ emission coefficients, and radiative lifetimes. • Experimental investigation of the new A´ 2Δ state should be significantly facilitated. A high-level theoretical approach – SA-CASSCF/MRCI – is used to explore the electronic structure and spectroscopic properties of a manifold of low-lying electronic states of the radical strontium monoiodide, SrI. For both Λ + S and Ω representations, potential energy curves are constructed, and the associated spectroscopic parameters derived. Dipole moment functions and vibrationally averaged dipole moments allow one to quantify the polarity of the various states. With the transition dipole moment functions, Einstein A v'v" coefficients for spontaneous emission were computed for pairs of selected states and radiative lifetimes evaluated for the low-lying vibrational levels of the excited electronic states. Reliable results are also provided for the yet unknown states A' 2Δ and E 2Σ+ which can guide spectroscopists to their experimental detection. Combined with recent theoretical work on SrF, SrCl, and SrBr one now can have a broad perspective of the trends in spectroscopic properties of this series of halides. [Display omitted] [ABSTRACT FROM AUTHOR]

• C1Π – X1Σ+, C1Π – A1Σ– and c3Π – a3Σ+ transitions are strong. • Lifetimes are 10 – 100 ns for the C1Π state and 10 μs for the c3Π state. • A1Σ– 1 – a3Σ+ 0– , B1Δ 2 – b3Δ 3 , b3Δ 2 – a3Σ+ 1 and d3Σ– 0+ – a3Σ+ 0– transitions are strong. • Lifetimes are 0.1 – 10, 10 and 0.1 – 1 ms for the B1Δ 2 , a3Σ+ 1 and b3Δ 2 states, respectively. • Lifetimes are 10–100, 10–100, and 100 μs for the A1Σ– 0– , d3Σ– 0+ and d3Σ– 1 states, respectively. The potential energy curves of the X1Σ+, A1Σ–, B1Δ, C1Π, a3Σ+, b3Δ, c3Π, and d3Σ– states of PO+ and the transition dipole moments between these states were calculated using the CASSCF method, and then the icMRCI approach. To accurately compute the transition properties, core–valence correlation and scalar relativistic corrections were taken into account. The spin–orbit coupling calculations were used to determine the transition properties of the A1Σ–, B1Δ, a3Σ+, and b3Δ states, from which no spontaneous emissions were generated owing to the limitations from the dipole–allowed transition selection rule. The radiative lifetime was approximately 10 – 100 ns for the C1Π state and 10 μs for the c3Π state. Among these dipole–allowed transitions, the emissions from the C1Π – X1Σ+ system was the strongest and was followed by the C1Π – A1Σ– and c3Π – a3Σ+ transitions. The radiative lifetime was approximately 10 – 100, 10 – 100, and 100 μs for the A1Σ– 0– , d3Σ– 0+ , and d3Σ– 1 states, respectively. Those were of the order of 0.1 – 10, 10, 10 – 100, 1 – 100, and 0.1 – 1 ms for the B1Δ 2 , a3Σ+ 1 , a3Σ+ 0– , b3Δ 1 , and b3Δ 2 states, respectively. Among the spontaneous emissions generated from these Ω states, those from the A1Σ– 1 – a3Σ+ 0– , A1Σ– 1 – a3Σ+ 1 , B1Δ 2 – b3Δ 3 , b3Δ 2 – a3Σ+ 1 , d3Σ– 0+ – a3Σ+ 0– , and d3Σ– 1 – a3Σ+ 1 transitions were relatively strong. The transition properties reported herein are expected to provide useful guidelines for the detection in future experiments. The radiative lifetimes are approximately 10 – 100 ns for the C1Π state and 10 μs for the c3Π state. Among all the dipole–allowed transitions involved in this study, the C1Π – X1Σ+ transition is the strongest and then followed by the C1Π – A1Σ– and c3Π – a3Σ+ transitions. The radiative lifetimes are approximately 10 – 100 μs for the A1Σ– 0– and d3Σ– 0+ states and 100 μs for the d3Σ– 1 state. The lifetimes are approximately 0.1 – 10, 10, 10 – 100, 1 – 100, and 0.1 – 1 ms for the B1Δ 2 , a3Σ+ 1 , a3Σ+ 0– , b3Δ 1 , and b3Δ 2 states, respectively. Among all these spontaneous emissions generated from A1Σ–, B1Δ, b3Δ, and d3Σ– states, those from the A1Σ– 1 – a3Σ+ 0– , A1Σ– 1 – a3Σ+ 1 , B1Δ 2 – b3Δ 3 , b3Δ 2 – a3Σ+ 1 , d3Σ– 0+ – a3Σ+ 0– , and d3Σ– 1 – a3Σ+ 1 transitions are strong. The dipole–allowed d3Σ–– c3Π transition is weaker than the spin–forbidden d3Σ– 0+ – a3Σ+ 0– transition; the dipole–allowed d3Σ– – c3Π transition is weaker than the spin–forbidden d3Σ– 1 – a3Σ+ 1 transition. [Display omitted] [ABSTRACT FROM AUTHOR]

• Spin-forbidden a − X , a ′ − X and spin-allowed A − X transition moments of CO were obtained using fully relativistic approach. • The radiative lifetimes of a 3 Π and A 1 Π states were evaluated as functions of vibrational and rotational quantum numbers. • The lifetimes derived for the a 3 Π state are in a near perfect agreement with their best experimental counterparts. • The intercombination transition probabilities were found to be almost strictly proportional to the squared fine structure constant α. The spin-forbidden a 3 Π − X 1 Σ + , a ′ 3 Σ + − X 1 Σ + and spin-allowed A 1 Π − X 1 Σ + electronic transitions dipole moments of carbon monoxide have been ab initio studied in the framework of multi-reference Fock space coupled cluster method combined with the finite-field approach and the generalized relativistic pseudo-potential model for the effective introducing the relativity in all-electron correlation treatment. Radiative lifetimes, τ i (v ′ , J ′) , of the upper i ∈ [ a 3 Π , A 1 Π ] states were evaluated as a function of vibrational, v ′ , and rotational, J ′ , quantum numbers. The τ a -values derived for the triplet a 3 Π 1 (0 , 1) and a 3 Π 2 (0 , 2) states at the highest level of computation were found to be 2.59 and 142 ms, which are near perfect agreement with their best experimental counterparts (J. J. Gilijamse, et al., J. Chem. Phys., 127 , 221102 (2007)). The intercombination a − X , a ′ − X transition probabilities were numerically proved to be proportional to α 2 , where α = e 2 / ℏ c is the fine structure constant. [ABSTRACT FROM AUTHOR]

• Lifetime is 100 ns for the B2Σ+ state. • Lifetimes are 10 ms for the a4Σ+ 3/2 and a4Σ+ 1/2 states and 10 µs for the A2Π 3/2 and A2Π 1/2 states. • Lifetimes are 1–10, 1, 10–100, and 1–10 µs for the A2Π, 22Π, 12Σ–, and C2Δ states, respectively. • A2Π – X2Σ+, B2Σ+ – X2Σ+, B2Σ+ – A2Π, 22Π – A2Π, and C2Δ – A2Π transitions are strong. • 22Π – B2Σ+, 12Σ– – 22Π, and C2Δ – 22Π transitions are weak. The transition dipole moments of the dipole–allowed transitions between the X2Σ+, A2Π, B2Σ+, 22Π, 12Σ–, and C2Δ states of the carbon monosulfide cation were calculated using the complete active space self–consistent field method, followed by the internally contracted multireference configuration interaction approach. The transition dipole moments of the spin–forbidden transitions from the a4Σ+ state to the X2Σ+ and A2Π states were computed. The radiative lifetimes were of the order of 1 – 10 µs, 100 ns, 1 µs, 10 – 100 µs, and 1 – 10 µs for the A2Π, B2Σ+, 22Π, 12Σ–, and C2Δ states, respectively. The transition frequencies, Einstein A coefficients, and Franck–Condon factors of all these spontaneous vibronic emissions from these systems were calculated. The emissions from the A2Π – X2Σ+, B2Σ+ – X2Σ+, B2Σ+ – A2Π, 22Π – A2Π, and C2Δ – A2Π systems were strong, suggesting that the 22Π state could be measured in a spectroscopy experiment via 22Π – A2Π transition. Those from the 22Π – B2Σ+, 12Σ– – 22Π, and C2Δ – 22Π systems were weak. The radiative lifetimes of the a4Σ+ 1/2 and a4Σ+ 3/2 states were approximately 10 ms. Among these spin–forbidden transitions, the emissions from the a4Σ+ 3/2 – A2Π 3/2 system were relatively strong. The radiative–lifetime distribution of each vibrational level versus the rotational quantum number was evaluated for the A2Π, B2Σ+, 22Π, 12Σ–, C2Δ, and a4Σ+ states. Image, graphical abstract The radiative lifetimes were approximately 1 – 10 µs, 100 ns, 1 µs, 10 – 100 µs, and 1 – 10 µs for the A2Π, B2Σ+, 22Π, 12Σ–, and C2Δ states, respectively. They were of the order of 10 ms for the a4Σ+ 3/2 and a4Σ+ 1/2 states and 10 µs for the A2Π 3/2 and A2Π 1/2 states. The A2Π – X2Σ+, B2Σ+ – X2Σ+, B2Σ+ – A2Π, 22Π – A2Π, and C2Δ – A2Π transitions were strong, and the 22Π – B2Σ+, 12Σ– – 22Π, and C2Δ – 22Π transitions were weak. The 22Π state could be measured spectroscopically via the 22Π – A2Π transition. Among the spin–forbidden transitions, the a4Σ+ 3/2 – A2Π 3/2 transition was relatively strong. The radiative lifetime of each level increased gradually with J for the A2Π, 22Π, 12Σ–, C2Δ, a4Σ+ 3/2 , and a4Σ+ 1/2 states. [ABSTRACT FROM AUTHOR]

• Lifetimes are 1–10, 0.1–1, and 1 μs for the A4Π, D4Σ–, and E4Π states, respectively. • Lifetimes are 10–100 and 1 – 10 μs for the d2Σ+ and e2Π states, respectively. • Lifetimes are 0.1–103 and 0.1–102 ms for the b2Δ and c2Σ– states, respectively. • Lifetimes are 1–104 and 1–103 ms for the B4Δ and C4Σ+ states, respectively. • A4Π – X4Σ–, D4Σ– – X4Σ–, E4Π – X4Σ–, and E4Π – A4Π transitions are strong. In this study, the potential energy curves were calculated for the X4Σ–, A4Π, B4Δ, C4Σ+, D4Σ–, E4Π, a2Π, b2Δ, c2Σ–, d2Σ+, and e2Π states of silicon boride. The transition dipole moments were computed for all dipole–allowed transitions between these states. The complete active space self-consistent field method was used for calculations, followed by the valence internally contracted multireference configuration interaction approach. The radiative lifetimes were approximately 1 – 10 μs, 0.1 – 1 μs, 1 – 10,000 ms, 1 – 1000 ms, and 1 μs for the A4Π, D4Σ–, B4Δ, C4Σ+, and E4Π states, respectively. Of these transitions between the six lowest–lying quartets, the spontaneous emissions from the A4Π – X4Σ–, D4Σ– – X4Σ–, E4Π – X4Σ–, and E4Π – A4Π systems were strong, whereas those from the B4Δ – A4Π, C4Σ+ – A4Π, and E4Π – B4Δ transitions were weak. The radiative lifetimes were approximately 0.1 – 1000 ms, 0.1 – 100 ms, 10 – 100 μs, and 1 – 10 μs for the b2Δ, c2Σ–, d2Σ+, and e2Π states, respectively. Of the transitions between the a2Π, b2Δ, c2Σ–, d2Σ+, and e2Π states, the spontaneous emissions from the e2Π – b2Δ and e2Π – c2Σ– systems were relatively strong, whereas those from the b2Δ – a2Π transition were relatively weak. The transition frequencies, Einstein A coefficients, and Franck–Condon factors of all spontaneous vibronic bands from these transitions were calculated. The results obtained in this study were compared with experimental and other theoretical values. The radiative–lifetime distribution varying with rotational angular quantum number J was calculated when J ≤ 50.5 for a particular vibrational level of these states. The radiative lifetimes are approximately 1 – 10, 0.1 – 1, 1, 10 – 100, and 1 – 10 μs for the A4Π, D4Σ–, E4Π, d2Σ+, and e2Π states, respectively; and those are of the order of 0.1 – 1000, 0.1 – 100, 1 – 10,000, 1 – 1000 ms for the b2Δ, c2Σ–, B4Δ, and C4Σ+ states, respectively. Of the transitions between the quartet states, the A4Π – X4Σ–, D4Σ– – X4Σ–, E4Π – X4Σ–, and E4Π – A4Π transitions are strong, whereas the B4Δ – A4Π, C4Σ+ – A4Π, and E4Π – B4Δ transitions are weak. Of the transitions between the doublet states, the e2Π – b2Δ and e2Π – c2Σ– transitions are relatively strong, whereas the b2Δ – a2Π transition is relatively weak. The radiative lifetime of a particular υ changes quickly as J increases for lower vibrational levels of the B4Δ, C4Σ+, b2Δ, c2Σ–, and d2Σ+ states; whereas the radiative lifetime of a particular υ increases or decreases as J increases for the other states. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The electronic structures of AsF are calculated with icMRCI+Q method. • Spectroscopic constants for bound states of AsF are obtained. • The radiative lifetimes of the transitions b1Σ+0+-X 1 3Σ−0+, A 2 3Π 0 + -X 1 3Σ−0+, A 3 3Π 1 -X 1 3Σ−0+, c'1Π 1 -X 1 3Σ−0+, a1 2 -X 2 3Σ−1, b1Σ+0+-X 2 3Σ−1, A 1 3Π 0 − -X 2 3Σ−1, A 2 3Π 0 + -X 2 3Σ−1, A 3 3Π 1 -X 2 3Σ−1, A 4 3Π 2 -X 2 3Σ−1 and c'1Π 1 -X 2 3Σ−1 are computed. High-level ab initio calculation on the 22 Λ-S electronic states of AsF has been performed with all-electron Gaussian basis sets and internally contracted multireference configuration interaction method plus Davidson correction (icMRCI+Q) and scalar relativistic effect. The spin-orbit coupling (SOC) has been investigated in the calculations by using the Breit-Pauli operator. After considering the SOC, the 22 Λ-S states of AsF split into 51 Ω states related to the lowest five dissociation limits. The spectroscopic constants of the bound states were obtained, which are found in better agreement with available experimental and theoretical results. Based on the computed potential energy curves (PECs), permanent dipole moments (PDMs), transition dipole moments (TDMs), Franck-Condon factors (FCFs) and radiative lifetimes have been acquired. This work should enhance our understanding of the electronic structure and spectroscopy information of AsF radical. [ABSTRACT FROM AUTHOR]

• Accurate spectroscopic constants are calculated with MRCI/aug-cc-pCV5Z-DK method. • The adiabatic spin-forbidden TMDs between six Ω states are also calculated. • The results by the state-of the-art ab initio method can update previous data. • The FCFs and radiative lifetimes are determined for potential applications. The spin-forbidden transitions of MgO are very important to the photodissociation dynamics and chemical reaction dynamics, which are frequently occurred in the interstellar space. In this work, the internally contracted multireference configuration interaction (icMRCI) method with the Davidson correction is used to compute the adiabatic potential energy curves (PECs) of eight Λ-S electronic states of MgO. Through considering the spin-orbit coupling (SOC) effect, the PECs of six splitting electronic states and the spin-forbidden transition dipole moments (TDMs) between the six lowest lying Ω states are also calculated. Using the calculated PECs and TDMs, the adiabatic transition parameters, including the Franck-Condon factors (FCFs) and radiative lifetimes for spin-forbidden transitions ( a 3 Π 0 + , 1 − X 1 Σ 0 + + and A 1 Π 1 − a 3 Π 0 + , 1 ), are determined. As for the a 3 Π 0 + , 1 − X 1 Σ 0 + + transition, the radiative lifetimes are shorter, which means the stronger emission could occur. The FCFs for the A 1 Π 1 − a 3 Π 0 + , 1 transition are highly diagonal and the values are greater than 0.94, but with large vibrational radiative lifetimes. The results obtained in this work are consistent with experimental ones and can be used to further investigate the mechanism of chemical reaction dynamics. [ABSTRACT FROM AUTHOR]

• Lifetimes are 10–4 s for the C4Δ state, and 10–7 s for the B4Σ– and E4Π states. • B4Σ– – X4Σ–, E4Π – X4Σ–, E4Π – A4Π, and E4Π – B4Σ– transitions are strong. • Lifetimes are 10–2 – 10–4 s for the D4Σ+ state and 10–3–10–4 s for the A4Π state. • Lifetimes are 10–5 s for the b2Σ– and d2Σ+ states, and 10–4–10–5 s for the c2Δ state. • E4Π – C4Δ and E4Π – D4Σ+ transitions are weak. Several experimental groups have measured the rovibrational transitions of B4Σ– – X4Σ–, 24Π – X4Σ–, B4Σ– – A4Π, and d2Σ+ – a2Π systems of diatomic boron carbide. However, no transition properties between any electronic states of this molecule have been calculated. This work studied the transition dipole moments between the X4Σ–, A4Π, B4Σ–, 14Δ, 14Σ+, and 24Π states, between the a2Π, b2Σ–, c2Δ, and d2Σ+ states, and from the a2Π 3/2 and a2Π 1/2 states to the X4Σ– 3/2 and X4Σ– 1/2 states. The radiative lifetimes are on the order of 10–2 – 10–4 s for the 14Σ+ state, 10–3 – 10–4 s for the A4Π state, 10–4 s for the 14Δ state, 10–4 – 10–5 s for the c2Δ state, 10–5 s for the b2Σ– and d2Σ+ states, and 10–7 s for the B4Σ– and 24Π states. The B4Σ– – X4Σ–, 24Π – X4Σ–, 24Π – A4Π, and 24Π – B4Σ– transitions are strong. The transitions from the a2Π 1/2 and a2Π 3/2 states to the X4Σ– 1/2 and X4Σ– 3/2 states are weak. The emissions originating from the a2Π 1/2 and a2Π 3/2 states at higher vibrational levels are easier to measure than those at lower levels. The radiative lifetimes are approximately 100 – 103 and 100 – 102 s for the a2Π 1/2 and a2Π 3/2 states, respectively. The band origins, Franck–Condon factors, and Einstein A coefficients of all dipole–allowed transitions were calculated. The distribution of radiative lifetime varying with rotational angular quantum number was investigated for the A4Π, B4Σ–, 24Π, b2Σ–, and d2Σ+ states. The transition properties reported in this work can provide useful guidelines for future experimental and theoretical studies. Image, graphical abstract The TDMs are calculated for the transitions between the six lowest–lying quartet states, between the four lowest–lying doublet states, and from the a2Π 1/2 and a2Π 3/2 states to the X4Σ– 1/2 and X4Σ– 3/2 states. The radiative lifetimes are approximately 10–2 – 10–4 s for the D4Σ+ state, 10–3 – 10–4 s for the A4Π state, 10–4 s for the C4Δ state, 10–4 – 10–5 s for the c2Δ state, 10–5 s for the b2Σ– and d2Σ+ states, and 10–7 s for the B4Σ– and E4Π states. The radiative lifetimes are on the order of several to several–thousand seconds for the a2Π 1/2 state and several to several–hundred seconds for the a2Π 3/2 state. The B4Σ– – X4Σ–, E4Π – X4Σ–, E4Π – A4Π, and E4Π – B4Σ– transitions are strong. The E4Π – C4Δ, E4Π – D4Σ+, a2Π 1/2 – X4Σ– 1/2 , a2Π 1/2 – X4Σ– 3/2 , a2Π 3/2 – X4Σ– 1/2 , and a2Π 3/2 – X4Σ– 3/2 transitions are weak. On the whole, the emissions originating from higher vibrational levels of the a2Π 1/2 and a2Π 3/2 states are stronger than those from lower levels. [ABSTRACT FROM AUTHOR]

• icMRCI+Q calculations are performed on AsBr with including the spin-orbit coupling effect. • Potential energy curves and spectroscopic constants for bound states are obtained. • Transition properties of b1Σ+ 0+ -X3Σ− 0+ , b1Σ+ 0+ -X3Σ− 1 and a1Δ 2 -X3Σ− 1 are reported. In this work, ab initio calculations on the low-lying electronic states of arsenic bromide (AsBr) have been carried out using the internally contracted multi-reference configuration interaction with the addition of Davidson correction (icMRCI+Q) method. The potential energy curves (PECs) of the 34 Λ-S states and the 74 Ω states generated from the Λ-S states after considering the spin-orbit coupling (SOC) effects are calculated. The spectroscopic constants of the typical bound states have been calculated and are compared with available experiment results. With the calculated spin-orbit matrix element we analyze the SOC-induced predissociation mechanisms of the a1Δ and b1Σ+ states. The permanent dipole moments (PDMs), transition dipole moments (TDMs), Frank-Condon factors (FCFs) and radiative lifetimes of some low-lying states have also been acquired, which would be of value to understand the transition properties. Our study should enhance our understanding on the electronic structure and spectroscopy of AsBr molecule. [ABSTRACT FROM AUTHOR]