Spectroscopic Constants Research Articles

Opacities of <inline-formula><tex-math id="Z-20220715033133-1">\begin{document}${ X}^1\Sigma^+_{\rm g}, a'{}^1\Sigma^-_{\rm u}, a{}^1\Pi_{\rm g} \text{ and } { b}^1\Pi_{\rm u}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715033133-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715033133-1.png"/></alternatives></inline-formula> electronic states for nitrogen molecule

Multi-reference configuration interaction (MRCI) approach with Davison size-extensivity correction (+Q) is employed to calculate the potential curves and dipole moments of <inline-formula><tex-math id="Z-20220715092522">\begin{document}${X^1}\Sigma _{\rm{g}}^ + ,{a^\prime }^1\Sigma _{\rm{u}}^ - ,{a^1}{\Pi _{\rm{g}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715092522.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715092522.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="Z-20220715092543">\begin{document}$b{}^1{\Pi _{\rm u}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715092543.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20220043_Z-20220715092543.png"/></alternatives></inline-formula> electronic states of N<sub>2</sub>. The spectroscopic constants and vibrational level spaceings are calculated and in excellent agreement with the available theoretical results and experimental data. Based on the calculated molecular structure parameters, the opacities of N<sub>2</sub> in a temperature range of 295–20000 K under a pressure of 100 atm (1 atm = 1.01×10<sup>5</sup> Pa) are presented. The results demonstrate that the wavelength range of absorption cross sections are enlarged with the temperature increasing. Moreover, the cross sections are mainly dominated in the range of ultraviolet for the cases with temperature <i>T</i> < 5000 K, while the obvious population can be found in the infrared ranges for the cases with temperature <i>T</i> > 10000 K due to the contribution of the excited states. The influence of temperature on the opacities of nitrogen molecule are investigated in the present work, which can provide theoretical and data support for researches of astrophysics and nuclear weapons.

Molecular opacities of <inline-formula><tex-math id="Z-20221003130318">\begin{document}$ {{\text{X}}^{2}}{\Sigma}_{\text{g}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130318.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130318.png"/></alternatives></inline-formula>, A<sup>2</sup>Π<sub>u</sub> and <inline-formula><tex-math id="Z-20221003130305">\begin{document}$ {{\text{B}}^{2}}{\Sigma}_{\text{u}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130305.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130305.png"/></alternatives></inline-formula> states of nitrogen cation

The potential curves, spectroscopic constants and dipole moments for <inline-formula><tex-math id="Z-20221003130344">\begin{document}$ {{\text{X}}^{2}}{\Sigma}_{\text{g}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130344.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130344.png"/></alternatives></inline-formula>, A<sup>2</sup>Π<sub>u</sub> and <inline-formula><tex-math id="Z-20221003130359">\begin{document}$ {{\text{B}}^{2}}{\Sigma}_{\text{u}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130359.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130359.png"/></alternatives></inline-formula> state of <inline-formula><tex-math id="M10">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M10.png"/></alternatives></inline-formula> are calculated by the internal contraction multi reference configuration interaction (icMRCI) method, with Davidson correction taken into consideration. According to the results of molecular structures, we present the partition function in a temperature range of 100–40000 K and the opacities at different temperatures (295, 500, 1000, 2000, 2500, 5000 and 10000 K) under a fixed pressure of 100 atm. It is found that the populations of excited states increase with temperature increasing, as a result, the wavelength range of opacity also increases and band boundaries for different transitions gradually become obscure. In comparison with the cases of N<sub>2</sub> with the same pressure and temperature, significant discrepancies are found in the wavelength ranges and structures of opacity of <inline-formula><tex-math id="M1119">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M1119.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M1119.png"/></alternatives></inline-formula> for the present work. The influence of temperature on the opacity of <inline-formula><tex-math id="M11">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M11.png"/></alternatives></inline-formula> is studied systematically in the present work, which is expected to provide theoretical and data support for astrophysics.

Rotationally resolved spectrum of the A2 A″-X2 A″ band of 1-indanyl radical

The rotationally resolved spectrum of the A2 A″-X2 A″ 000 band of jet-cooled 1-indanyl near 473 nm is recorded by laser induced fluorescence with a spectral resolution of ~0.014 cm−1. Accurate spectroscopic constants for both A2A″ and X2 A″ states of 1-indanyl are determined from rotational analysis of the experimental spectrum. These indicative spectroscopic parameters are applied to test the calculated structure of 1-indanyl. The calculations show good agreements with the experimental data. Based on the computational molecular orbitals and spin densities for 1-indanyl, the delocalization of unpaired pπ electron that stabilizes the 1-indanyl radical is discussed.

Rotational spectroscopy of the argon dimer by time-resolved Coulomb explosion imaging of rotational wave packets

We report time-domain rotational spectroscopy of the argon dimer, Ar2, by implementing time-resolved Coulomb explosion imaging of rotational wave packets. The rotational wave packets are created in Ar2 with a linearly polarized, nonresonant, ultrashort laser pulse, and their spatiotemporal evolution is fully characterized by measuring angular distribution of the fragmented Ar+ promptly ejected from Ar22+ generated by the more intense probe pulse. The pump-probe measurements have been carried out up to a delay time of 16 ns. The alignment parameters, derived from the observed images, exhibit periodic oscillation lasting for more than 15 ns. The pure rotational spectrum of Ar2 is obtained by Fourier transformation of the time traces of the alignment parameters. The frequency resolution in the spectrum is about 90 MHz, the highest ever achieved for Ar2. The rotational constant and the centrifugal distortion constant are determined with much improved precision than the previous experimental results: B0 = 1.72713 ± 0.00009 GHz and D0 = 0.0310 ± 0.0005 MHz. The present B0 value does not match within the quoted experimental uncertainty with that from the VUV spectroscopy, so far accepted as an experimental reference to assess theories. The present improved constants would stand as new references to calibrate state-of-the-art theoretical investigations and an indispensable experimental source for the construction of an accurate empirical intermolecular potential.

Synchrotron-based far-infrared spectroscopy of [formula omitted]: Extended ro-vibrational analysis and new line list up to 3360 cm[formula omitted

The far-infrared spectrum of HC3N has been recorded at high resolution between 70 and 500 cm−1using synchrotron radiation. Four prominent features, i.e., ν7, ν6−ν7, ν4−ν6, and 2ν7 have been identified in the spectrum together with many associated hot bands. In addition, rotational transitions for the interacting v4=v7=1, (v6=2,v7=1), (v5=1,v7=2), and v7=5 vibrationally excited states have been recorded in the millimeter/submillimeter region. The newly assigned transitions, together with those reported previously, form a comprehensive data set including about 17 000 transitions, which involves almost all the vibrational states of HC3N lying below 1300 cm−1 plus some excited states with energies between 2075 and 3550 cm−1. These data have been fitted to an effective Hamiltonian which takes into account rotational and vibrational l-type resonance effects, together with a number of anharmonic interaction terms. On average, all the analysed data are reproduced within the experimental accuracy. About 90 000 rotational and ro-vibrational transition frequencies have been computed on the basis of the spectroscopic constants obtained from the global fit in order to support data interpretation and astronomical searches in the interstellar medium and planetary atmospheres. Part of these data is included in the 2020 release of the HITRAN database.

Assessing the Accuracy of Tailored Coupled Cluster Methods Corrected by Electronic Wave Functions of Polynomial Cost.

Tailored coupled cluster theory represents a computationally inexpensive way to describe static and dynamical electron correlation effects. In this work, we scrutinize the performance of various coupled cluster methods tailored by electronic wave functions of polynomial cost. Specifically, we focus on frozen-pair coupled cluster (fpCC) methods, which are tailored by pair-coupled cluster doubles (pCCD), and coupled cluster theory tailored by matrix product state wave functions optimized by the density matrix renormalization group (DMRG) algorithm. As test system, we selected a set of various small- and medium-sized molecules containing diatomics (N2, F2, C2, CN+, CO, BN, BO+, and Cr2) and molecules (ammonia, ethylene, cyclobutadiene, benzene, hydrogen chains, rings, and cuboids) for which the conventional single-reference coupled cluster singles and doubles (CCSD) method is not able to produce accurate results for spectroscopic constants, potential energy surfaces, and barrier heights. Most importantly, DMRG-tailored and pCCD-tailored approaches yield similar errors in spectroscopic constants and potential energy surfaces compared to accurate theoretical and/or experimental reference data. Although fpCC methods provide a reliable description for the dissociation pathway of molecules featuring single and quadruple bonds, they fail in the description of triple or hextuple bond-breaking processes or avoided crossing regions.

The eight lowest-energy vibrational states of benzonitrile: analysis of Coriolis and Darling-Dennison couplings by millimeter-wave and far-infrared spectroscopy

A combination of millimeter-wave and high-resolution infrared data is used to analyze the eight lowest-energy vibrational states of benzonitrile (C6H5CN, C2v, μa = 4.5 D), a benzene derivative recently detected in the interstellar medium. The overtone states v22 = 2 and v33 = 2, combination state v22 = 1, v33 = 1, and fundamental states v21 = 1 and v15 = 1 are studied for the first time by rotationally resolved spectroscopy. The three former states form a Coriolis- and Darling-Dennison-coupled triad of interacting states for which the coupling terms and highly precise, deperturbed energy separations have been measured. The use of sub-millimeter and far-infrared data together enabled the determination of the purely rotational and coupling parameters for the six lowest-energy vibrationally excited states of benzonitrile, along with their highly precise energies (E22 = 141.4810252 (57) cm−1, E33 = 160.5891953 (47) cm−1, E2×22 = 282.6295417 (83) cm−1, E22+33 = 302.5795909 (87) cm−1, E2×33 = 321.4923856 (77) cm−1, E21 = 372.257993 (10) cm−1). These energies, the resultant experimental anharmonicity constants (x22,22 = − 0.1663 cm−1, x33,33 = 0.1570 cm−1, and x22,33 = 0.4909 cm−1), and semi-experimental harmonic frequencies (ω22 = 142.9 cm−1 and ω33 = 161.0 cm−1) for the ν22 and ν33 states are compared to CCSD(T)/ANO1 predicted values. The spectroscopic and coupling constants determined in this work for the vibrational ground state, the two lowest-energy fundamental states, and the corresponding first overtone and combination states successfully predict experimental frequencies down to 8 GHz. Particularly for the vibrationally excited states, the ability to predict transition frequencies so far outside the frequency region in which the constants were determined confirms that the rotational and distortion constants, as well as the coupling terms, are determined reasonably close to their true values. The ability to accurately extrapolate also demonstrates the suitability of the determined constants as the basis for extraterrestrial identification and examination of these vibrational states of benzonitrile.

Rotational spectra and conformational analysis of 2-bromobutane

The rotational spectra of 2-bromobutane were obtained by using a chirped-pulse Fourier-transform microwave (CP-FTMW) spectrometer in the frequency range 8–18 GHz. Hyperfine structures of both bromine isotopologues (I = 3/2) for the three conformers (G+, A, and G−) have been investigated to determine the rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants of bromine (Br). The conformational compositions for G+, A, and G− in the supersonic jet, estimated by relative intensity measurements, are 55%, 28%, 17%, respectively, for the 79Br species, and 52%, 33%, 15%, respectively, for the 81Br species. However, the small zero-point energy differences of isotopomers can be negligible and can be considered as an average value instead of individual values, which is 54%, 30%, 16% for G+, A, and G− species. The nuclear quadrupole coupling tensors (χxx, χyy, and χzz) of Br and the quadrupolar angles were obtained, and the χzz value of 2-bromobutane is compared with those of other alkyl bromides. The spectroscopic constants, rs coordinates of Br and the dipole moments of the most stable G+ conformer are predicted well from the ab initio calculations at the MP2/6–311++G(2d,2p) level.

Exploring the low-lying electronic states of AsO including spin–orbit interaction

In this paper, the multireference configuration interaction method (MRCI) combined with the Davidson correction (+Q) is used to study the high-level ab initio calculation of AsO electronic states. The potential energy curves (PECs) of 27 Λ-S states and 18 Ω states related to the three lowest dissociation limits are obtained. According to these PECs, the spectroscopic constants of Λ-S and Ω states can be calculated, which is little different from the previous experimental values. The dipole moments (DMs) of the Λ-S state is also calculated. In addition, the transition properties of several transitions are calculated, including the transition dipole moments (TDMs), Franck-Condon factors (FCFs) and spontaneous radiative lifetimes of Λ-S state. This work should improve our understanding of the electronic structure and spectroscopic information of AsO.

Near-infrared and Visible Opacities of S-type Stars: The B1Π—X1Σ+ Band System of ZrO

Abstract The ZrO B1Π—X1Σ+ transition is an important opacity source in the near-infrared and optical spectrum of S-type stars. The 0–0, 0–1, 0–2, 1–0, 1–2, 1–3, 2–0, 2–1, 2–3, 2–4, 3–1, 3–4, and 4–2 bands of the 90Zr16O B1Π—X1Σ+ transition are reanalyzed using a high-temperature (2390 K) high-resolution (0.04 cm−1) emission spectrum collected at the National Solar Observatory (Kitt Peak). A modern spectroscopic analysis was performed using the PGOPHER program to provide updated spectroscopic constants and to produce a high-precision line list with line strengths based on an ab initio calculation of the transition dipole moment.

Ab initio calculation of the ground and first excited states of the lithium dimer

Based on a high level ab initio calculation which is carried out with the multireference configuration interaction method under the aug-cc-pVXZ (AVXZ) basis sets, X = T, Q, 5, the accurate potential energy curves (PECs) of the ground state and the first excited state of Li2 are constructed. By fitting the ab initio potential energy points with the Murrell–Sorbie potential function, the analytic potential energy functions (APEFs) are obtained. The molecular bond length at the equilibrium (R e ), the potential well depth (D e ), and the spectroscopic constants (B e , ω e , α e , and ω e χ e ) for the state and the state are deduced from the APEFs. The vibrational energy levels of the two electronic states are obtained by solving the time-independent Schrödinger equation with the Fourier grid Hamiltonian method. All the spectroscopic constants and the vibrational levels agree well with the experimental results. The Franck–Condon factors (FCFs) corresponding to the transitions from the vibrational level (v′ = 0) of the ground state to the vibrational levels (v″ = 0–74) of the first excited state have been calculated. The FCF for the vibronic transition of (v″ = 0) ←(v′ = 0) is the strongest. These PECs and corresponding spectroscopic constants provide reliable theoretical references to both the spectroscopic and the molecular dynamic studies of the Li2 dimer.

The effect of spin-orbit coupling on molecular properties: Potential energy curve, transition dipole moment and laser cooling scheme of NH

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 (X3Σ-, a1Δ, b1Σ+ and A3Π) and eight Ω states (X3Σ0+,1-,a1Δ2, b1Σ0++ and A3Π0-,0+,1,2) of NH molecule are obtained by the multi-reference configuration interaction (MRCI) plus Davidson correction. The spectroscopic constants (Re, ωe, ωeχe, Be, De) 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 X3Σ0+-↔A3Π1, X3Σ1-↔A3Π0+ and X3Σ1-↔A3Π0- transitions are considered. The feasible laser cooling schemes using a single laser are formulated. In the proposed cooling scheme, there wavelengths for the X3Σ0+-↔A3Π1 are used, the main pump lasers are λ00 = 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.

Electronic Structures and Transition Properties of BeSe and BeTe Molecules.

The electronic structure of BeSe and BeTe molecules has been investigated using the ab initio CASSCF/(MRCI + Q) method at the spin-free and spin-orbit level. The potential energy curves, the permanent dipole moment, the spectroscopic constants Te, Re, ωe, and Be, and the dissociation energy De are determined in addition to the vertical transition energy Tv. The molecules’ percentages of ionic character are deduced, and the trends of the spectroscopic constants of the two molecules are compared and justified. A ro-vibrational study is performed using the canonical function approach to calculate the constants Ev, Bv, and Dv and the turning points Rmin and Rmax. All the ground-state vibrational levels have also been investigated. The radiative lifetimes of vibrational transitions among the electronic ground states are also discussed. The results for BeSe have been compared with the previously published data while those for BeTe molecules are presented here for the first time.

Extensive spin–orbit multi-reference study on low-lying electronic states of HgI

The multireference configuration interaction (MRCI) method with inclusion of Davidson correction (+Q) and spin-orbit coupling (SOC) effects is adopted to compute the electronic structures of the low-lying states of HgI. The potential energy curves (PECs) of 14 Λ-S states correlated with the first and second dissociation limits together with 30 low-lying Ω states are calculated. The spectroscopic constants of bound states are obtained, which agree well with the available experimental values. With the assistance of calculated SOC matrix elements, the perturbations on the vibrational levels of the C2Π caused by nearby state are analyzed. Finally, the spontaneous radiative lifetimes of bound states are evaluated, which are in consistence with existing measurements.

Theoretical electronic structure with rovibrational studies of the molecules YP, YP+ and YP-

Due to the absence of the electronic structure of the YP molecule and its ions in literature, this work is conducted via an ab initio Complete Active Space Self Consistent Field and the Multi-Reference Configuration Interaction with Davidson correction calculation (CASSCF/MRCI + Q) to investigate the low–lying electronic states of these molecules. Adiabatic potential energy curves (PECs) along with static dipole moment (DM) curves for 27, 24, and 21 low-lying electronic states in the representation of 2s+1Λ(+/−) for YP, YP+, and YP- molecules have been investigated, respectively. For the low-lying electronic states of the YP molecule and their anion and cation, the spectroscopic constants Re, Te, ωe, ωexe, Be, De are provided. The rovibrational constants Ev, Bv, Dv, and the abscissa of turning points Rmin and Rmax (up to vibrational level v = 37) are calculated using the canonical functions approach and referring to the calculated data from the PECs. Perturbation theory method is also used to compare our data's validity, as no results are presented in the literature for these molecules.

Van der Waals molecules consisting of a zinc or cadmium atom interacting with an alkali-metal or alkaline-earth-metal atom

Alkaline-earth-like transition-metal atoms such as Zn and Cd are promising candidates for precision measurements and quantum many-body physics experiments. Here, we theoretically investigate the properties of diatomic molecules containing these closed-shell atoms. We calculate potential energy curves, permanent electric dipole moments, and spectroscopic constants for molecules consisting of either a Zn or Cd atom interacting with an alkali-metal (Li, Na, K, Rb, Cs, Fr) or alkaline-earth-metal (Be, Mg, Ca, Sr, Ba, Ra) atom. We use the ab initio electronic structure coupled cluster method with single, double, and triple excitations combined with large Gaussian basis sets and small-core relativistic energy-consistent pseudopotentials for heavier atoms. We predict that the studied molecules in the ground electronic state are chemically reactive weakly bound van der Waals complexes with small permanent electric dipole moments. The present results may be useful for spectroscopy and application of the studied molecules in modern ultracold physics and chemistry experiments.

Line positions, intensities, and Einstein A coefficients for 3–0 band of 12C16O: A spectroscopy learning method* *Project supported by the Open Research Fund of Computational Physics Key Laboratory of Sichuan Province, Yibin University (Grant No. YBXYJSWLZD- 2020-006), the Funds for Sichuan Distinguished Scientists of China (Grant Nos. 2019JDJQ0050 and 2019JDJQ0051), the National Natural Science Foundation ofChina (Grant Nos. 61722507 and

Based on the model- and data-driven strategy, a spectroscopy learning method that can extract the novel and hidden information from the line list databases has been applied to the R branch emission spectra of 3–0 band of the ground electronic state of 12C16O. The labeled line lists such as line intensities and Einstein A coefficients quoted in HITRAN2020 are collected to enhance the dataset. The quantified spectroscopy-learned spectroscopic constants is beneficial for improving the extrapolative accuracy beyond the measurements. Explicit comparisons are made for line positions, line intensities, Einstein A coefficients, which demonstrate that the model- and data-driven spectroscopy learning approach is a promising and an easy-to-implement strategy.

Electronic Structure of RhO2+, Its Ammoniated Complexes (NH3)1-5RhO2+, and Mechanistic Exploration of CH4 Activation by Them.

High-level electronic structure calculations are initially performed to investigate the electronic structure of RhO2+. The construction of potential energy curves for the ground and low-lying excited states allowed the calculation of spectroscopic constants, including harmonic and anharmonic vibrational frequencies, bond lengths, spin-orbit constants, and excitation energies. The equilibrium electronic configurations were used for the interpretation of the chemical bonding. We further monitored how the Rh-O bonding scheme changes with the gradual addition of ammonia ligands. The nature of this bond remains unaffected up to four ammonia ligands but adopts a different electronic configuration in the pseudo-octahedral geometry of (NH3)5RhO2+. This has consequences in the activation mechanism of the C-H bond of methane by these complexes, especially (NH3)4RhO2+. We show that the [2 + 2] mechanism in the (NH3)4RhO2+ case has a very low energy barrier comparable to that of a radical mechanism. We also demonstrate that methane can coordinate to the metal in a similar fashion to ammonia and that knowledge of the electronic structure of the pure ammonia complexes provides qualitative insights into the optimal reaction mechanism.

Molecular structure and properties of MgCa molecule

• Investigation of 13 electronic states using MRCI approach with 4 basis sets. • New assignment of the experimental electronic states. • Spectroscopic and ro-vibrational constants with experimental comparisons. • Franck-Condon factors for vibronic transitions. • Vibrational Branching equipped with calculated lifetimes for laser cooling studies. Experimentally, when the MgCa molecule was studied, certain ambiguity occurred, and an ab initio calculation was requested. For this reason, an extensive study is carried out regarding the electronic structure of MgCa. A new and improved assignment of experimental molecular states is allocated. The accuracy of the adopted ab initio approach is proven in different aspects through our work when agreements are attained between two different experimental approaches and the present work. Theoretical studies of the MgCa compound are performed within the framework of the multi-reference configuration interaction method using 4 different basis sets in order to reach optimal accuracy. The potential energy curves, permanent dipole moments, spectroscopic constants ( T e , ω e , B e , and R e ), and ro-vibrational constants ( G v , B v , D v , R m i n , and R m a x ) are investigated for 13 electronic states. Nine new states are studied here for the first time. The Franck-Condon factors, transition dipole moments at R -centroid, vibrational branching including transition rates, and lifetimes are considered for the states required for laser cooling schemes. Since the focus of this study is devoted to an accurate description of the ground and lowest electronic excited states, we also constructed RKR potentials from the experimental Dunham-type coefficients and computed the spectroscopic and ro-vibrational constants for comparison sake.

The ground state van der Waals potentials of Cd-RG systems

Assuming that the corresponding states principle is valid for the hetero-nuclear dimers formed from group 12 and rare gas atoms, that is, the reduced potentials of Cd-RG and Hg-RG systems are conformal, together with the dispersion coefficients C6, C8, and C10 calculated from the combining rules with the parameters of Cd-Cd and RG-RG, the van der Waals potentials of Cd-RG can be described by the TT potential. According to the present potential curves of Cd-RG, the spectroscopic constants of these dimers can be obtained. The present results of Cd-RG are compared with available experimental and theoretical results of other studies.