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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]

High-level electronic structure calculations were conducted for LiC molecule and compared to other theoretical results. The potential energy curves (PECs) for the 18 states originating from the first three dissociation channels of LiC molecule were calculated by the internally contracted multireference configuration interaction method. The spectral constants and vibrational energy levels are reported. The transition properties for the a2Π, b2Δ, c2Σ−, d2Σ+, and 22Π states are discussed. In addition, the spin-orbit coupling effects were taken into account in the electronic transition d2Σ+–a2Π. The b2Δ and c2Σ− states had radiative lifetimes of approximately 0.03–16.83 and 0.86–8.06 ms, respectively. The d2Σ+ and 22Π states had radiative lifetimes of approximately 1.94–64.83 and 0.31–16.59 µs, respectively. Between these transitions, the emissions from the d2Σ+–a2Π, 22Π–c2Σ−, 22Π–b2Δ, and 22Π–a2Π systems were strongest, while the emissions from the c2Σ−–a2Π, b2Δ–a2Π, and 22Π–d2Σ+ systems were weaker. The d2Σ+1/2 state had radiative lifetimes of approximately 3.75–29.81 µs. Among the spontaneous emissions of the transitions generated by the d2Σ+1/2 state, the emissions from the d2Σ+1/2–a2Π1/2 and d2Σ+1/2–a2Π3/2 systems were relatively strong and easily observed experimentally. The radiative lifetime variation law with the rotational quantum number for the d2Σ+1/2 state at rotational quantum number J ≤ 70 and vibrational quantum number ν ≤ 15 is also presented in this paper. In addition, almost all the strong emissions of the transitions were distributed in the infrared region. It is expected that the results of this study will serve as a helpful reference for future experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

The potential energy curves of the X1Σ+, a3Σ+, b3Π, and c3Δ states of NS+ and the properties of the transitions between them are reported, which were calculated using the complete active space self–consistent field method, followed by the internally contracted multireference configuration interaction approach with Davidson correction. The radiative lifetimes of the first 16 vibrational levels were 11.3–68.3 μs and 0.18–530.7 ms for the b3Π and c3Δ states, respectively; those were 40.9–47.4 ms for the a3 state; those were 22.3–130.5, 11.7–63.5, 22.2–131.7, and 23.8–143.6 μs for the b3Π2, b3Π1, b3Π0+, and b3Π0– states, respectively; those were 0.1–350.3, 0.2–964.5, and 0.4–2247.1 ms for the c3Δ1, c3Δ2, and c3Δ3 states, respectively. The radiative lifetime of the a3 state was extremely long. The spectroscopic parameters and vibrational levels were evaluated and compared with the available experimental and theoretical results. The Franck–Condon factors, band origins, and Einstein A coefficients of all these spontaneous emissions were determined. The b3Π–a3Σ+ transition was strong and hence easy to be detected. [ABSTRACT FROM AUTHOR]

The values of the radiative parameters for atomic cobalt were determined using a semi-empirical method. The eigenvector amplitudes determined in our previously published research were adopted. In most cases, the calculated values of the oscillator strengths and radiative lifetimes agree well with the experimental data. Predictions of the values of the radiative parameters are also provided. • A semi-empirical parametrization of the radiative parameters for Co I. • A good agreement of calculated and experimental values was achieved. • The predicted values of radiative parameters not yet experimentally were determined. [ABSTRACT FROM AUTHOR]

By employing the general-purpose relativistic atomic structure package (GRASP) based on fully relativistic multiconfiguration Dirac-Fock (MCDF) method, energies and radiative lifetimes of levels have been reported for four times ionized xenon (Xe V). In calculations, the Breit interactions for relativistic effects, quantum electrodynamical (QED) contributions have been included as a perturbation, as well as electron correlation effects (VV, CV and CC). We have compared the results obtained in this work with experimental and theoretical values in available literature for Xe V. We have obtained good agreement with previous works. [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]

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.

The carrier losses due to radiative recombination in monolayer transition metal dichalcogenides are studied using fully microscopic many-body models. The density- and temperature-dependent losses in various Mo- and W-based materials are shown to be dominated by Coulomb correlations beyond the Hartree-Fock level. Despite the much stronger Coulomb interaction in 2D materials, the radiative losses are comparable-if not weaker-than in conventional III-V materials. A strong dependence on the dielectric environment is found in agreement with experimental results.

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]

• The 7 low-lying Λ-S states associated with the two lowest dissociation limits of the SeH are investigated by MRCI+Q approach. • On considering SOC effect, the 14 Ω states generated from the 7 Λ-S states are yielded. • The spectroscopic constants of the bound Λ-S and Ω states are accurately extracted. • We analyze the spin-orbit perturbations to the bound A2Σ+ state and develop a SOC induced predissociation mechanism of the A2Σ+ state. • The equilibrium ground state geometry is optimized using RCCSD(T) method. High-level ab initio calculations are performed to investigate potential energy curves (PECs) of seven low-lying Λ-S states associated with the two lowest dissociation limits of the SeH radical by utilizing the internally contracted multireference configuration interaction (icMRCI) method in combination with the aug -cc-pwCV5Z Gaussian basis set. The scalar relativistic effect (SR), the electronic core-valence (CV) correction, and Davidson (+ Q) modification are included in our calculations. The fourteen Ω states generated from the seven Λ-S states are yielded when the spin-orbit coupling (SOC) effect is taken into account by using the Breit-Pauli operator. On the ground of the obtained PECs, the spectroscopic constants of the bound Λ-S and Ω states are evaluated, which reproduce pretty well the available experimental and theoretical values. By virtue of SOC matrix elements between the bound A2Σ+ state and repulsive 4Σ–(I), 2Σ–(I), or 4∏(I) states crossing with the A2Σ+ state PEC, the spin-orbit perturbations in the A2Σ+ rovibrational manifold in the crossing region and the A-state predissociation mechanism are analyzed. It is clearly exhibited that the avoided crossing phenomena between electronic states possessing the same Ω quantum number provide obvious spectroscopic effects in the transition dipole moments (TMDs) and Franck-Condon factors (FCFs) of the A2Σ+-X2Π transition. The radiative lifetimes of the A2Σ+ vibrational sublevels are determined. In addition, we finalized our study of the SeH molecule by optimizing its equilibrium ground state geometry in terms of a restricted coupled cluster approach including singles and doubles with perturbative triples account (RCCSD(T) method) plus CV, SR, and SOC corrections with extrapolating to complete basis set (CBS) limit. An amplified view of PECs crossings of the A2Σ+, 4Σ–(I), 2Σ–(I), and 4П(I) states with vibrational energy levels of A2Σ+ near crossing points. As described in the below figure, the adjacent repulsive 4Σ–(I), 2Σ–(I), and 4П(I) states PECs intersect with the bound A2Σ+ state PEC at the v ′=0, 1, and 1–2, respectively. It indicates that, the predissociation channels of A2Σ+→4Σ–(I) (ν ′≥0), A2Σ+→2Σ–(I) (ν ′≥1), and A2Σ+→4П(I) (ν ′≥2) would be open by SOC perturbation around the three crossing points, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

The values of the radiative parameters for single ionised cobalt were determined using a semi-empirical method. The eigenvector amplitudes determined in our previously published research were adopted. In most cases, the calculated values of oscillator strengths and radiative lifetimes agree well with the experimental data. The results were also compared with the available theoretical calculations. • A semi-empirical parameterisation of the radiative parameters for Co II is presented. • A good agreement of calculated and experimental values was achieved. • The obtained results were compared with other calculated data available. • The values of radiative parameters not yet experimentally determined are predicted. [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]

Lifetime calculations of Th II J = 1.5 and 2.5 odd states are performed with configuration–interaction many-body perturbation theory (CI-MBPT). For many J = 2.5 states, lifetimes are quite accurate, but two pairs of J = 2.5 odd states and many groups of J = 1.5 states are strongly mixed, making theoretical predictions unreliable. To solve this problem, a method based on intensities is used. To relate experimental intensities to lifetimes, two parameters, one an overall coefficient of proportionality for transition rates and one temperature of the Boltzmann distribution of populations, are introduced and fitted to minimize the deviation between theoretical and intensity-derived lifetimes. For strongly mixed groups of states, the averaged lifetimes obtained from averaged transition rates were used instead of individual lifetimes in the fit. Close agreement is obtained. Then intensity branching ratios are used to extract individual lifetimes for the strongly mixed states. The resulting lifetimes are compared to available directly measured lifetimes and reasonable agreement is found, considering limited accuracy of intensity measurements. The method of intensity-based lifetime calculations with fit to theoretical lifetimes is quite general and can be applied to many complex atoms where strong mixing between multiple states exists.

The ab initio quasirelativistic approach developed specifically for the calculation of spectral parameters of highly charged ions has been used to determine transition data for the Mo-like tungsten ion W 32 +. The configuration interaction method is utilized to include electron correlation effects. The relativistic effects are taken into account in the Breit–Pauli approximation. Level energies, radiative lifetimes τ , Landé g -factors are determined for the ground configuration 4p 6 4d 6 and two excited configurations 4p 5 4d 7 and 4p 6 4d 5 4f. The radiative transition wavelengths λ , emission transition probabilities A , weighted oscillator strengths g f , and transition line strengths S for the electric dipole, electric quadrupole, electric octupole, magnetic dipole, and magnetic quadrupole transitions among the fine-structure levels of these configurations are produced. The uncertainties of computed spectroscopic parameters are 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]

Radiative lifetimes of the ro-vibrational bound states of HeLi + ( b 3 ∑ + ) are calculated quantum-mechanically when both bound-bound and bound-free processes are taken into account. The calculations are restricted to the initial states with low rotational quantum numbers. For the rotationless molecular ion, the shortest lifetime is 1.30 × 10 - 6 s of the ground vibrational state. With increasing vibration excitations the radiative lifetimes slightly increase, but keep below 10 - 5 s for the next 17 vibrational states, then they start to increase more rapidly up to 2.41 × 10 - 2 s for the highest vibrational state. The radiative lifetimes also tend to slightly prolong with increasing rotational excitations but stay on the same magnitude for the low rotational quantum numbers. [ABSTRACT FROM AUTHOR]

• Ab initio PECs, TDMs and partition functions of AlO are calculated. • Comparisons of radiative lifetimes and line intensities of AlO are given. • Temperature-dependent spectroscopy below 55,000 cm−1 is presented. • The electronic transitions from X2Σ+ to A2Π, B2Σ+, C2Π and D2Σ+ are important. The spectrum of AlO is widely used in various applications including the explorations of interstellar space, studies of laser ablation, combustions of Al-containing fuels and so on. In this work, we reported the spectroscopy of the AlO radical at temperatures of 300 ∼ 15,000 K for the wavenumber range of 1 ∼ 55,000 cm−1. Firstly, we extended our previous calculations of the potential energy curves (PECs) and transition dipole moments (TDMs) for AlO (Bai, Qin & Liu, MNRAS, 2022, 510:1649–1656) to higher B2Σ+, D2Σ+, 1′2Π and 1′'2Π electronic states, with the consideration of Davidson correction, scalar relativistic correction and core-valence correlation. Partition functions, Einstein coefficients and radiative lifetimes of AlO were then obtained by solving the nuclear-motion Schrödinger equation. The partition functions reveal that the AlO molecules mainly exist in the X2Σ+ state at temperatures of 10 ∼ 6270 K and in the A2Π state at temperatures of 6270 ∼ 15,000 K in the thermodynamic equilibrium. Finally, line intensities and spectra for different electronic transitions of AlO were calculated. The results show that the X2Σ+ → C2Π and X2Σ+ → D2Σ+ transitions dominate in the ultraviolet waveband. Comparisons of the TDMs, radiative lifetimes, line intensities and spectra with previous theoretical and experimental values indicate that our calculated data in the ultraviolet waveband are reliable and may be used for the radiation field calculation. [Display omitted] [ABSTRACT FROM AUTHOR]

Accurate radiative transition probabilities of diatomic electronic systems are required to calculate the discrete radiation of plasmas. However, most of the published transition probabilities are obtained using older spectroscopic constants and electronic transition moment functions (ETMFs), some of which deviates greatly from experimental data. Fortunately, a lot of new spectroscopic constants that include more anharmonic correction terms than the earlier ones have been published over the past few years. In this work, the Einstein coefficients, Franck–Condon factors and absorption band oscillator strengths are calculated for important diatomic radiative transition processes of N 2 -O 2 , CO 2 -N 2 and H 2 plasmas produced in entering into the atmosphere of Earth, Mars and Jupiter. The most up-to-date spectroscopic constants are selected to reconstruct the potential energy curves by the Rydberg–Klein–Rees (RKR) method. Then the vibrational wave functions are calculated through the resolution of the radial Schrödinger equation for such potential energy curves. These results, together with the latest “ab-initio” ETMFs derived from the literature are used to compute the square of electronic-vibrational transition moments, Einstein coefficients and absorption band oscillator strengths. Moreover, the Franck–Condon factors are determined with the obtained vibrational wave functions. In the supplementary material we present tables of the radiative transition probabilities for 40 band systems of N 2 , N 2 + , NO, O 2 , CO, CO + , CN, C 2 and H 2 molecules. In addition, the calculated radiative lifetimes are systematically validated by available experimental results. [ABSTRACT FROM AUTHOR]

With the purpose of providing the spectroscopic parameters that can contribute to future identification of calcium fluoride (CaF) molecule in sunspot, interstellar and circumstellar environments, the present work by focusing mainly on the astrophysically significant molecule CaF, provides the qualitative study of i) the transition probability parameters like Franck–Condon factors and r-centroids for the electronic transitions C–X, D–X, E–X, C–B, C–B’ and E’–A and ii) the transition moment, oscillator strength, Einstein coefficients, vibrational temperature and radiative lifetimes of the higher electronic state E, using the derived transition probability parameters for E–X transition. The evaluated transition probability parameters reveal the astrophysical importance of CaF molecular transitions and they are discussed elaborately using the spectroscopic technique. Based on the present calculations, radiative lifetimes for the vibrational levels from 1 to 5 for the state E are predicted to be 14.0, 21.9, 36.1, 82.8, 97.0 ns respectively and it is found that the calculated values are in excellent agreement with the experimental results reported earlier. The observed vibrational temperature of 1451 ± 134 K for the electronic transition E–X also favors the prediction of the existence of CaF molecule in cold sunspot. [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]

Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (AΣ) and the first excited (AΣ) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs, Li and Na cores, parameterized l-dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the AΣ state using the Franck-Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the AΣ state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice. [ABSTRACT FROM AUTHOR]

The potential energy curves and transition dipole moments for the 1 2 Σ + , 2 2 Σ + , 1 2 Π and 2 2 Π electronic states of the two molecules are calculated using multi-reference configuration interaction and the large basis sets aug-cc-pwCV5Z. 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 motion, and the spectroscopic parameters are then obtained by fitting the energy levels to Dunham series expansions. The spin-orbit coupling effect of the 2 Π states for both the BH + cation and BH − anion are calculated. Highly diagonally distributed Franck-Condon factors are determined for the 1 2 Σ + (v″ = 0) ↔ 1 2 Π (v′ = 0) transition, ƒ 00 (BH + ) = 0.943, while the Franck-Condon factors for the 1 2 Π (v″ = 0) ↔ 1 2 Σ + (v′ = 0) transition is ƒ 00 (BH − ) = 0.942. Moreover, the radiative lifetime of 38.2 ns for the excited 1 2 Π state of the BH + and 91.8 ns for the 1 2 Σ + state of the BH − are obtained, which are short enough for rapid laser cooling. A three-step optical scheme of the laser cooling is constructed for either the BH + cation or the BH − anion. [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]

We investigate the linewidths and radiative lifetimes of single InAs quantum dots embedded in the ternary matrix Al x Ga ( 1 − x ) As as a function of aluminum composition. For an increasing aluminum content, we find that the average of the measured linewidths of individual transitions increases. Furthermore, we find that the distribution of the measured linewidths broadens. We infer that the linewidth broadening is the result of spectral wandering caused by inhomogeneities and local defects in the surrounding Al x Ga ( 1 − x ) As matrix. Local charging and de-charging of defects polarize quantum dots in their vicinity thereby shifting the energy states of the exciton transition in time through the quantum confined Stark effect. The intrinsic radiative lifetimes of numerous quantum dots were determined. We suggest that the observed variation in radiative lifetime at a given photon energy is explained by the influence of an in-plane electric field on the oscillator strength of the electron–hole pair. [ABSTRACT FROM AUTHOR]

The aim of this paper is to determine the radiative lifetimes of selected levels for Sc II and Ti II based on the results of a semi-empirical oscillator strengths parametrization. The calculated values of the lifetimes are, in the majority of cases, in very good agreement with accurate experimental data. Moreover, the predicted values of the radiative lifetimes will be useful in case when the experimental values are not known. [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]

The potential energy curves (PECs) of 9 Λ-S states (X 2 Σ + , 1 4 Σ + , 1 6 Σ + , A 2 Π, 1 4 Π, 1 6 Π, 1 4 Δ, 1 4 Σ − , 2 4 Π) and corresponding 28 Ω states of PN + cation are calculated by the complete active space self-consistent field (CASSCF), which is followed by the internally contracted multireference configuration interaction (icMRCI) with Davidson modification. The calculation is taken into account these effects of spin–orbit coupling, core–valence correlation and scalar relativistic correction. These are found that the 2 4 Π, 1 6 Π and 1 4 Σ − states possess double wells and two avoided crossings occur between the 1 6 Π and 2 6 Π states, the 2 4 Π and 3 4 Π states. Based on the PECs, the spectroscopic parameters are evaluated. And the transitions (transition dipole moments, Franck–Condon Factors and radiative lifetimes) from 1 6 Π −1/2 and 2 4 Π −1/2 (the first well of the two states) to the ground state X 2 Σ + 1/2 are obtained in this paper. These effects of spin–orbit coupling, core–valence correlation and scalar relativistic correction on the spectroscopic calculations are analyzed. [ABSTRACT FROM AUTHOR]

High-level ab initio calculations on the ground and the excited states of the SrH molecule have been carried out utilizing the multi-reference configuration interaction method plus Davidson correction (MRCI+Q) method, with small-core relativistic effective core potentials together with the corresponding correlation consistent polarized valence basis sets. The potential energy curves (PECs) of the 16 Λ–S states have been obtained with the aid of the avoided crossing rule between electronic states of the same symmetry. The spectroscopic constants of the bound states were calculated, most of which have been reported for the first time, with those pertaining to the X 2 Σ + , A 2 П, B 2 Σ + , and A′ 2 Δ states being in line with the available experimental and theoretical values. The calculated spin–orbit matrix element indicates a strong interaction between the X 2 Σ + and A 2 П states in the Franck–Condon region. The spin–orbit coupling (SOC) splits the lowest strongly bound X 2 Σ + , A 2 П, A′ 2 Δ, B 2 Σ + , and D 2 Σ + states into 9 Ω states. For the D 2 Σ + state, the SOC shifts the potential-well minimum to higher energy and shortens the bond length. The transition properties of the bound Λ–S states were predicated, including the transition dipole moments (TDMs), the Franck–Condon factors, and the radiative lifetimes. The lifetimes were calculated to be 34.2 ns ( v ′=0) and 55.0 ns ( v ′=0) for A 2 П and B 2 Σ + , in good agreement with the experimental results of 33.8±1.9 ns and 48.4±2.0 ns. [ABSTRACT FROM AUTHOR]

The absorption and emission spectroscopic behavior of alloxazine is studied in aqueous solutions at pH 4 (10 −4 M HCl) and pH 10 (10 −4 M NaOH). At pH 4 only the pure form of alloxazine is present, while at pH 10 about 9% of alloxazine is present in its tautomeric form of isoalloxazine. Absorption cross-section spectra, fluorescence emission quantum distributions, fluorescence excitation quantum distributions, excitation wavelength dependent fluorescence quantum yields, fluorescence lifetimes, and radiative lifetimes are determined. The spectroscopic behavior of alloxazine at pH 4 and pH 10 is compared with that of 7,8-dimethyl-alloxazine (lumichrome) at pH 4 and pH 10. Photo-induced (excited-state) tautomerization of alloxazine to isoalloxazine is observed which does not occur for lumichrome. In the case of alloxazine the highest occupied molecular n orbital (n-HOMO) is energetically well below the highest occupied molecular π orbital (π-HOMO) giving non-degenerate ground-state to first excited-state (ππ*) transition. For isoalloxazine, lumichrome, and lumichrome-10H-tautomer n-HOMO is only slightly below π-HOMO causing photo-induced ground-state n → π electron transfer with elongation of fluorescence lifetime and radiative lifetime. [ABSTRACT FROM AUTHOR]

• Semi-empirical parametrization of the radiative parameters for atomic chromium was performed. • Radiative lifetimes for low-lying metastable Cr I levels were determined. • Possible clock transition in the chromium atom was proposed. • For the clock transition suitable detection schemes were proposed and experimentally investigated. In this article radiative parameters for atomic chromium were determined by a semi-empirical method. The eigenvector amplitudes, determined in our previously published work concerning the hyperfine structure parametrization for even-parity atomic chromium levels, were used. The calculated values of oscillator strengths and lifetimes for low-lying metastable Cr I levels are presented. On the basis of the calculations performed, a possible clock transition in neutral chromium is proposed. Possible detection schemes for the clock transition were investigated experimentally and are presented in this work. [ABSTRACT FROM AUTHOR]

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]

The potential energy curves of 20 Λ-S states of BP yeilded from the first two dissociation limits B(2Pu) + P(4Su) and B(2Pu) + P(2Du) have been calculated by the internally contracted multireference configuration interaction approach with the Davidson correction. Especially the core-valence correlation and scalar relativistic corrections are included in the present work. Potential energy curves are also extrapolated to the complete basis set limit. According to the potential energy curves, the spectroscopic parameters are determined and compared with those available in the literature. The convergent behavior of the present calculations is discussed with respect to the basis set and level of theory. Of the 20 states, the 23∑- and 33∑- states have the avoided crossings, which are very weakly bound ones, the 21∑-, and the 13Δ and 23Δ states possess a double well. Subsequently, the transition dipole moments, Franck-Condon factors, and radiative times of the transitions 31Π-b1Π, 23Δ-X3Π, 23∑--A3∑-, 33∑--A3∑-, and 15∑--15Π are calculated. [ABSTRACT FROM AUTHOR]

The ground and low-lying excited states of MgLi and MgLi+molecules have been investigated. The potential energy curves and the permanent and transition dipole moments of the MgLi and MgLi+molecules are determined making use of the multi-reference configuration interaction and valence full configuration interaction with large basis sets. The core–valence correlation and scalar relativistic correction are also taken into account with aug-cc-pCVQZ basis set and the third-order Douglas–Kroll Hamiltonian approximation, respectively. The transition dipole moments are used to evaluate the radiative lifetimes of the vibrational levels for the low-lying excited states of the MgLi and MgLi+molecules. The derived spectroscopic constants of the ground and low-lying excited states are in good agreement with available experimental and theoretical works. [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]

The ab initio quasirelativistic Hartree–Fock method developed specifically for the calculation of spectroscopic parameters of heavy atoms and highly charged ions was used to derive spectral data for the multicharged tungsten ion W 35+ . The configuration interaction method was applied to include the electron-correlation effects. The relativistic effects were taken into account in the Breit–Pauli approximation for quasirelativistic Hartree–Fock radial orbitals. The energy level spectra, radiative lifetimes τ , and Lande g -factors have been calculated for the 4p 6 4d 3 , 4p 6 4d 2 4f, and 4p 5 4d 4 configurations of the W 35+ ion. [ABSTRACT FROM AUTHOR]

Highlights: [•] Accurate spectroscopic constants of these bond states are obtained. [•] The spin–orbit-induced predissociation of the A 3Π state is calculated. [•] Einstein coefficients and F–C factors for the A 3Π − X system have been calculated. [•] DM functions and radiative lifetime for the A 3Π state has also been determined. [Copyright &y& Elsevier]

Highlights: [•] High-level ab initio calculation including spin–orbit effects. [•] State-of-the-art excited states potential energy curves description. [•] Accurate electronic and vibrational spectra. [•] Transition moments, transition probabilities, radiative lifetimes. [•] Suggests that C 2Σ+ −X 2Σ+ transitions will not be observed, differently than BeCl. [ABSTRACT FROM AUTHOR]