Theoretical electronic structure with spin-orbit coupling effect of the molecules SrAt and BaAt for laser cooling studies.

Ab initio CASSCF/MRCI + Q calculations have been used to investigate the electronic structure and transition properties of the alkaline earth astatine molecules SrAt and BaAt. The adiabatic potential energy curves have been computed and plotted for the low-lying electronic states in the representations 2S+1Λ+/- and Ω(±) (with and without spin-orbit coupling effect). The spectroscopic and vibrational constants have been deduced for the corresponding bound states. An analysis of the Franck-Condon factors, the Einstein Coefficients, and the branching ratios among different vibrational levels has shown that both SrAt and BaAt molecules are suitable candidates for Doppler and Sysphus laser cooling. Experimental laser cooling schemes and conditions for these two molecules have been proposed. These results may pave the way for new spectroscopic and laser cooling experiments of alkaline earth astatine molecules.

Electronic structure with spin-orbit coupling effect of HfH molecule for laser cooling investigations.

The electronic structure, including the spin-orbit coupling effect of the HfH molecule, has been studied to determine if it can be cooled through Doppler and Sysphus laser cooling techniques. The multi-reference configuration interaction plus Davidson correction (MRCI + Q) method has been used to calculate its potential energy curves (P.E.C.s) in the Ω(±) and 2s+1Ʌ(+/-) representation. The spectroscopic constants Te, Re, ωe, Be, αe, the dipole moment µe, and the dissociation energies De agree very well with previously published work. In addition, we present in this work twenty new doublet and quartet states in the Ω(±) representation. The electronic transition dipole moment curves (TDMCs) between the lowest-lying electronic states have been investigated for the Δ - Π, Π - ∑+ and Δ - Φ transitions among specific Ω(±) states. The Franck-Condon factors (FCFs), the Einstein coefficient of spontaneous emission [Formula: see text] , and the radiative lifetime τ have been computed for the investigated transitions. In addition, properties of the molecules' electronic and vibrational states, such as the static dipole moment curves (D.M.C.s), the ionic character fionic, and the rovibrational constants are calculated. We deduce from our results that the HfH molecule is indeed a laser-cooling candidate that can reach a temperature as low as the nK regime. We present a complementary scheme with suitable experimental parameters. These results can be of great interest to experimental spectroscopists interested in ultracold diatomic molecules and their applications.

Theoretical study of the CO2-O2 van der Waals complex: potential energy surface and applications.

A four-dimensional-potential energy surface (4D-PES) of the atmospherically relevant carbon dioxide-oxygen molecule (CO2-O2) van der Waals complex is mapped using the ab initio explicitly correlated coupled cluster method with single, double, and perturbative triple excitations (UCCSD(T)-F12b), and extrapolation to the complete basis set (CBS) limit using the cc-pVTZ-F12/cc-pVQZ-F12 bases and the l-3 formula. An analytic representation of the 4D-PES was fitted using the method of interpolating moving least squares (IMLS). These calculations predict that the most stable configuration of CO2-O2 complex corresponds to a planar slipped-parallel structure with a binding energy of V ∼ -243 cm-1. Another isomer is found on the PES, corresponding to a non-planar cross-shaped structure, with V ∼ -218 cm-1. The transition structure connecting the two minima is found at V ∼ -211 cm-1. We also performed comparisons with some CO2-X van der Waals complexes. Moreover, we provide a SAPT analysis of this molecular system. Then, we discuss the complexation induced shifts of CO2 and O2. Afterwards, this new 4D-PES is employed to compute the second virial coefficient including temperature dependence. A comparison between quantities obtained in our calculations and those from experiments found close agreement attesting to the high quality of the PES and to the importance of considering a full description of the anisotropic potential for the derivation of thermophysical properties of CO2-O2 mixtures.

Laser cooling and electronic structure of Be halide anions BeX- (X = Cl, Br, F, and I).

The adiabatic potential energy curves of the low lying electronic states of the Be halide anions BeX- (Cl, Br, F, and I) have been investigated in the representation 2s+1Λ(+/-) by using the complete active space self-consistent field with a multireference configuration interaction method. The spectroscopic parameters Te, Re, ωe, and Be and the static and transition dipole moment µe were studied, and a rovibrational study of the investigated electronic states was performed. New electronic states were investigated here for the first time. The calculated highly diagonal Franck-Condon factor and the short radiative lifetime among the lowest vibrational levels of the X1Σ0+ - (1)3Π1 transitions of the molecular anion BeF- prove its candidacy for Doppler laser cooling. The experimental proof of the stability and the calculated experimental parameters, such as the vibrational branching ratio, the slowing distance, the recoil, and Doppler temperatures with the experimental conditions of the buffer gas cell of this anion, open the route for experimental work on the BeF- molecular ion.

Laser Cooling with an Intermediate State and Electronic Structure Studies of the Molecules CaCs and CaNa.

The ground and excited electronic states of the diatomic molecules CaCs and CaNa have been investigated by implementing the ab initio CASSCF/(MRCI + Q) calculation. The potential energy curves of the doublet and quartet electronic low energy states in the representation 2s+1Λ(±) have been determined for the two considered molecules, in addition to the spectroscopic constants T e, ωe, B e, R e, and the values of the dipole moment µe and the dissociation energy D e. The determination of vibrational constants E v, B v, D v, and the turning points R min and R max up to the vibrational level v = 100 was possible with the use of the canonical functions schemes. Additionally, the transition and the static dipole moments curves, Einstein coefficients, the spontaneous radiative lifetime, the emission oscillator strength, and the Franck-Condon factors are computed. These calculations showed that the molecule CaCs is a good candidate for Doppler laser cooling with an intermediate state. A "four laser" cooling scheme is presented, along with the values of Doppler limit temperature T D = 55.9 µK and the recoil temperature T r = 132 nK. These results should provide a good reference for experimental spectroscopic and ultra-cold molecular physics studies.

A theoretical electronic structure with a feasibility study of laser cooling of LaNa molecules with a spin orbit effect.

The electronic structure with the spin orbit effect of the molecule LaNa has been studied in the present work using the Multi-Reference Configuration Interaction MRCI calculations including Davidson correction (+Q). Adiabatic potential energy curves (PECs) have been investigated for the lowest low-lying spin free states in the Λ representation and spin orbit states of Ω = 0+/-, 1, 2, 3, and 4 along with their spectroscopic constants Re, Te, ωe, and Be, the dissociation energy De, the dipole moment µe, and the ionic character fionic of the LaNa molecule at the equilibrium bond length. The permanent dipole moment curves (PDMCs) for the investigated states are calculated in addition to the electronic transition dipole moments between the lowest electronic states where the Franck-Condon factor (FCF) has been calculated for the X1Σ+-11Π and for many spin orbit transitions. For these transitions the dipole moments are used in order to determine the Einstein coefficient of spontaneous emission Aν'ν, the radiative lifetime τ and the branching ratio Rν'ν. Employing the canonical function approach, the rovibrational parameters Eν, Bν, Dν, Rmin and Rmax have also been calculated for the lowest vibrational levels of different bound states in both Λ and Ω representations. To the best of our knowledge, the data reported in the present work are presented for the first time in the literature with a discussion on the candidacy of this molecule for laser cooling.

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.

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 T e, R e, ωe, and B e, and the dissociation energy D e 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 E v, B v, and D v and the turning points R min and R max. 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.

Rovibronic spectroscopy of PN from first principles.

We report an ab initio study on the rovibronic spectroscopy of the closed-shell diatomic molecule phosphorous mononitride, PN. The study considers the nine lowest electronic states, X 1Σ+, A 1Π, C 1Σ-, D 1Δ, E 1Σ-, a 3Σ+, b 3Π, d 3Δ and e 3Σ- using high level electronic structure theory and accurate nuclear motion calculations. The ab initio data cover 9 potential energy, 14 spin-orbit coupling, 7 electronic angular momentum coupling, 9 electric dipole moment and 8 transition dipole moment curves. The Duo nuclear motion program is used to solve the coupled nuclear motion Schrödinger equations for these nine electronic states and to simulate rovibronic absorption spectra of 31P14N for different temperatures, which are compared to available spectroscopic studies. Lifetimes for all states are calculated and compared to previous results from the literature. The calculated lifetime of the A1Π state shows good agreement with an experimental value from the literature, which is an important quality indicator for the ab initio A-X transition dipole moment.

Ab-initio calculations of the electronic structure of the alkaline earth hydride anions XH- (X = Mg, Ca, Sr and Ba) toward laser cooling experiment.

By the use of the ab initio CASSCF/(MRCI+Q) calculations in the representation 2s+1Λ(+/-), the adiabatic potential energy curves and the dipole moment curves of the low lying states of the alkaline earth hydride anions (MgH-, CaH-, SrH- and BaH-) have been investigated in their singlet and triplet multiplicities. The spectroscopic parameters Te, Re, ωe, Be, αe, the dipole moment µe, and the dissociation energy De have been also calculated for the bound states of the considered molecules. In addition, a systematic investigation of the transition dipole moment curves for the lowest 1Σ+-1Π transitions has been done along with the Franck-Condon factor (FCF) corresponding to the X1Σ+-(1)1Π transition. Using the canonical function approach, a rovibrational study has been performed for finding the rovibrational constants Ev, Bv, Dv and the turning points Rmin and Rmax for the ground and different excited bound state. Efficient routes may be achieved via the diagonal FCF for the formation of cold and ultracold alkaline earth hydride anions. PACS N: 31.10. + z, 31.15.A, 31.15.vn, 31.50.Df.

Electronic Structure Calculations with the Spin Orbit Effect of the Low-Lying Electronic States of the YbBr Molecule.

This work presents an electronic structure study employing multireference configuration interaction MRCI calculations with Davidson correction (+Q) of the ytterbium monobromide YbBr molecule. Adiabatic potential energy curves (PECs), dipole moment curves, and spectroscopic constants (such as R e, ωe, B e, D e, T e, and µe) of the low-lying bound electronic states are determined. The ionic character of the YbBr molecule at the equilibrium position is also discussed. With spin-orbit effects, 30 low-lying states in Ω = 1/2, 3/2, 5/2, 7/2 representation are probed. The electronic transition dipole moment is calculated between the investigated states and then used to determine transition coefficients, for example, the Einstein coefficient of spontaneous emission A ij and emission oscillator strength f ij . Vibrational parameters such as E ν, B ν, D ν, R min, and R max of the low vibrational levels of different bound states in both Λ and Ω representations are also calculated. Upon calculating the Franck-Condon factors, they are found to be perfectly diagonal between three couples of low-lying excited states. Vibrational Einstein coefficients and radiative lifetimes are computed as well for the lowest vibrational transitions. Most of the data reported in this work are presented here for the first time in the literature. Very good accordance is obtained in comparison with the previously reported constants by means of experimental methods.

Electronic Structure with Rovibrational Calculations of the Magnesium Monohalides MgX and Their Cations MgX+ (X = Cl, Br, and I).

Alkaline-earth monohalides are popular compounds that are used in various applications. Little is known, however, in terms of electronic structure, about their cations and their low-lying electronic states. We present in this work electronic structure ab-initio calculations based on multireference configuration interaction plus Davidson correction of three magnesium monohalides and their cations (MgCl, MgBr, MgI, MgCl+, MgBr+, and MgI+). We determine the spectroscopic constants T e, R e, ωe, B e, and αe and the dissociation energies D e for their bound states. Additionally, we investigate their vibrational properties by calculating the vibrational eigenvalue E v, the rotational constant B v, and the centrifugal distortion constant D v. We additionally study the electric charge distribution of several states by determining their permanent dipole moment and transition dipole moment curves. Finally, we calculate the Franck-Condon factors and the radiative lifetimes as precursors for laser cooling experiments.

Electronic structure of the polar molecules XF (X: Be, Mg, Ca) with rovibrational and dipole moment calculations.

A theoretical investigation for the feasibility of laser-cooling is performed through the calculation of accurate potential energy curves, static dipole moments, spectroscopic constants and rovibrational calculations for 24, 26 and 27 highly excited electronic states for BeF, CaF and MgF molecules respectively. In order to understand the electronic structure of their lowest lying electronic states and to learn the characteristic behavior of their chemical bonding, a high level of calculation is realized by using the complete active space self-consistent field (CASSCF) with multi-reference configuration interaction MRCI method including single and double excitations with Davidson correction (+Q) for the three considered molecules. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. Fifty new excited electronic states have been investigated, in the present work, for the first time for the three studied molecules.