Search

A new silicon monoxide (28Si16O) line list covering infrared, visible, and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the $A\, {}^{1}\Pi$ and $E\, {}^{1}\Sigma ^{+}$ electronic states. Strong perturbations to the $A\, {}^{1}\Pi$ band system are accurately modelled through the treatment of six dark electronic states: $C\, {}^{1}\Sigma ^{-}$, $D\, {}^{1}\Delta$, $a\, {}^{3}\Sigma ^{+}$, $b\, {}^{3}\Pi$, $e\, {}^{3}\Sigma ^{-}$, and $d\, {}^{3}\Delta$. Along with the $X\, {}^{1}\Sigma ^{+}$ ground state, these nine electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin–orbit, electronic angular momentum, and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the X–X, E–X, and A–X electronic systems through the MARVEL (Measured Active Rotational–Vibrational Energy Levels) procedure. 112 observed forbidden transitions from the C–X, D–X, e–X, and d–X bands were assigned using our predictions, and these could be fed back into the MARVEL procedure. The SiOUVenIR line list was computed using published ab initio transition dipole moments for the E–X and A–X bands; the line list is suitable for temperatures up to 10 000 K and for wavelengths longer than 140 nm. SiOUVenIR is available from www.exomol.com and the CDS data base.

An accurate global potential energy surface (PES) for the HBr2 system has been constructed using the fundamental invariant neural network fitting method based upon 11 698 ab initio energies at the UCCSD(T)/CBS level of theory, with the spin-orbit coupling of the 2P3/2 orbit of the Br atom properly included. The time-dependent wave packet calculations have been performed to study the H + Br2 → HBr + Br reaction on the new PES. The total reaction probabilities for total angular momentum J = 0 for the ground initial state show no threshold due to the submerged barrier height (-0.351 kcal/mol) of the PES. The total integral cross sections (ICS) for reactant Br2 in ro-vibrational states (v0 = 0, j0 = 0, 10, 20, 30; v0 = 1-5, j0 = 0) were calculated for collision energy of up to 0.5 eV. It is found that the initial rotational excitation has a negligible effect on the ICS, and the initial vibrational excitation depresses the reactivity to some extent. The thermal rate constants for the title reaction in the temperature range of 100-1000 K were calculated from the Boltzmann averaging of the v0 = 0-5 rate constants, which overestimated the experimental results to some extent.

International audience; We present a study of the O(3P) + C2H4 scattering reaction, a process that takes place in the interstellar medium and is of relevance in atmospheric chemistry as well. A comprehensive investigation of the electronic properties of the system has been carried out based on multiconfigurational ab initio CASSCF/CASPT2 calculations, using a robust and consistent active space that can deliver accurate potential energy surfaces in the key regions visited by the system. The paper discloses detailed description of the primary reaction pathways and the relevant singlet and triplet excited states at the CASSCF and CASPT2 level, including an accurate description of the critical configurations, such as minima and transition states. The chosen active space and the CASSCF/CASPT2 computational protocol are assessed against coupled-cluster calculations to further check the stability and reliability of the entire multiconfigurational procedure.

One of the most interesting anomalies in nuclear physics is the island of inversion (IOI), which indicates that the magic numbers disappear. It provides a good platform to understand single-particle motion, many-body correlation, and nucleon-nucleon interaction. In neutron-rich isotopes near N =20 area, many experiments have found that the spectra, electromagnetic transitions, radii, and two-neutron separation energies of these nuclei are abnormal. This region is called the N =20 IOI, because it is characterized by neutron particle-hole excitations related to deformation from the 1s0d shell into the 1p0f shell across the N =20 shell gap. Recent experiments show that the ground states of 29Ne and 28F have negative parities, indicating that these two nuclei are within the N =20 IOI. This provides new opportunities and challenges for theoretical models in this area. With the standard shell model, the N =20 IOI has been proved by many works to have a strong cross-shell effect between 1s0d and 1p0f shells. They proposed that the tensor force and three-nucleon force should have an important influence on the microscopic description of neutron-rich nuclei in this area, especially in Ne and Mg isotopes. However, the N =20 IOI is still rarely studied in ab initio calculations. Recently, an extension of the ab initio valence-space in-medium similarity renormalization group method was presented to study the physics of neutron-rich nuclei by Miyagi et al. In the present paper, based on chiral force including nucleon-nucleon and three-nucleon force, we have performed ab initio calculations for the low-lying states of 28F and 29Ne, focusing on the relative excitation energies of the positive- and negative-parity states in these nuclei. In order to study the effect of three-nucleon force on the N =20 IOI, we use nucleon-nucleon force at N3LO with or without three-nucleon force at N2LO in our calculations. Using the open-shell many-body perturbation theory, the cross shell sd-pf realistic effective Hamiltonian, including single-particle energies and effective two-body interactions, is constructed self-consistently without introducing parameters. The constructed effective Hamiltonian is diagonalized with the shell model method. In shell model calculation, we use a truncation with up to five nucleons (including protons and neutrons) occupying the pf orbit. The low-lying states of 28F and 29Ne are calculated with NN and NN+3N interactions. The results show that three-nucleon force is important in the descriptions of low-lying states of 28F and 29Ne, especially in 29Ne while the first negative state turned to be ground state due to the three-nucleon force. Our calculations give that three-nucleon force gives large effects for the relative position between the 0d3/2 and 1p3/2 single-particle orbitals, causing the two orbitals to reverse. Furthermore, the configurations of low-lying states of 28F and 29Ne are calculated within our ab initio calculations with NN+3N interaction. The results give that the lowest positive and negative parity states in 28F and 29Ne are dominated by 2 ℏ ω and 1 ℏ ω components, respectively. We have also calculated the configurations of the ground state in neutron-rich even-even Ne isotopes, and the results indicate that the three-nucleon force could enhance the cross-shell excitations in the nuclei in the vicinity of IOI, which is essential for the exotic properties of these nuclei. Furthermore, we have also performed the phenomenological shell model calculations with SDPF-MU effective interactions, and the results are similar to our ab initio calculations including three-nucleon force.

Despite several studies in the literature, the detailed quantum state-to-state level mechanism of the astrophysically important exoergic barrierless H + LiH+ → H2 + Li+ reaction is yet to be understood. In this work, we have investigated the energy disposal mechanism of the reaction in terms of integral reaction cross section, product internal state distributions, differential cross section, and rate constant. Fully converged and Coriolis coupled quantum mechanical calculations based on a time-dependent wave packet method have been performed at the state-to-state level on the ab initio electronic ground state potential energy surface (PES) constructed by Martinazzo et al. (J. Chem. Phys. 2003,119, 11241-11248). The agreement between the present quantum mechanical and previous quasi-classical results is found even at very low relative translational energies of reagents. A non-statistical inverse Boltzmann vibrational distribution for the product is found. This is attributed to the "attractive" nature of the underlying PES, which facilitates the excess energy release mostly as product vibration (60-80%). The energy disposal in products is found to be unaffected by the rovibrational excitation of the reagent diatom due to the weak coupling between the vibrational modes of the reagent and the product. The mild effect of collision energy on the product energy disposal is ascribed to the effective coupling between the translational modes of the reagent and the product. It is found that the collisions lead to the formation of the product H2 in its rovibrationally excited levels.

In this theoretical study, we investigate the electronic potential energy curves, spectroscopic parameters, vibrational energy levels and transition dipole moments for the diatomic dications BeRb2+, BeCs2+, and SrRb2+. We consider an ab initio approach based on the use of non-empirical pseudopotentials and parameterized l dependent polarization potentials. Results show that 1-22Σ+ for BeRb2+, 1-52Σ+ for BeCs2+, and 1-32Σ+ for SrRb2+ are repulsive. While the 32Σ+ for BeRb2+, 42Σ+ for BeCs2+, and 42Σ+ for SrRb2+ are metastable states. These states can accommodate some vibrational energy levels. Interesting avoided crossings between some 2Σ+ states are localized and examined. Until now, no experimental and theoretical studies have been made for each system. Consequently, we discuss our results by comparing with some data on similar systems. Besides, the transition dipole moments of the ground state to a few excited states are computed and presented. The information associated with the electronic structures, spectroscopic parameters as well as the transition properties provided in this paper, is anticipated to serve as guidelines for further experimental and theoretical research on diatomic dications considered in this work.

We use ab initio real-time time-dependent density functional theory to investigate the effect of optical and extreme ultraviolet (XUV) circularly polarized femtosecond pulses on the magnetization dynamics of ferromagnetic materials. We demonstrate that the light induces a helicity-dependent reduction of the magnitude of the magnetization. In the XUV regime, where the 3p semicore states are involved, a larger helicity dependence persisting even after the passage of light is exhibited. Finally, we were able to separate the part of the helicity-dependent dynamics due to the absorption from the part due to the inverse Faraday effect. Doing so, we show that the former has, overall, a greater impact on the magnetization than the latter, especially after the pulse and in the XUV regime. This work hints at the yet experimentally unexplored territory of the XUV light-induced helicity-dependent dynamics, which, according to our prediction, could magnify the helicity-dependent dynamics already exhibited in the optical regime.

We present very accurate theoretical results of Penning ionization rate coefficients of the excited metastable helium atoms (4He(23S) and 3He(23S)) colliding with the hydrogen isotopologues (H2, HD, D2) in the ground and first excited rotational and vibrational states at subkelvin regime. The calculations are performed using the current best ab initio interaction energy surface, which takes into account the nonrigidity effects of the molecule. The results confirm a recently observed substantial quantum kinetic isotope effect (Nat. Chem. 2014, 6, 332–335) and reveal that the change of the rotational or vibrational state of the molecule can strongly enhance or suppress the reaction. Moreover, we demonstrate the mechanism of the appearance and disappearance of resonances in Penning ionization. The additional model computations, with the morphed interaction energy surface and mass, give better insight into the behavior of the resonances and thereby the reaction dynamics under study. Our theoretical findings are compared with all available measurements, and comprehensive data for prospective experiments are provided.

The dynamics of the H + H2+ reaction has been analyzed from the electronically first excited state of diabatic potential energy surfaces constructed by employing the Beyond Born-Oppenheimer theory [J. Chem. Phys. 2014, 141, 204306]. We have employed the coupled 3D time-dependent wavepacket formalism in hyperspherical coordinates for multisurface reactive scattering problems. To be specific, the charge transfer processes have been investigated extensively by calculating state-to-state as well as total reaction probabilities and integral cross sections, when the reaction process is initiated from the first excited electronic state (21A'). We have depicted the convergence profiles of reaction probabilities for the competing charge transfer processes, namely, reactive charge transfer (RCT) and nonreactive charge transfer (NRCT) processes for different total energies with respect to total angular momentum, J. Total and state-to-state integral cross sections are calculated as a function of total energy for the initial rovibrational state, namely, v = 0, j = 0 level of H2+ (2Σg+) molecule and are compared with previous theoretical calculations. Finally, we have calculated temperature-dependent rate constants using our presently evaluated cross sections and compared their average with the experimentally measured one.

Ab initio multi-configuration Dirac–Fock (MCDF) calculations are performed for energy levels and lifetimes of the lowest 115 fine-structure levels generated from the 3s23p63d7, 3s23p53d8, 3s3p63d8, 3s23p43d9, and 3s3p53d9 configurations of Hf XLVIII, Ta XLIX, Os LII, Pt LIV, and Au LV of fusion interest. Furthermore, radiative rates are calculated for all electric dipole, electric quadrupole, magnetic dipole, and magnetic quadrupole transitions. Electron correlation is treated through multi-configuration expansions in the active space approximation. The Breit interaction and the leading quantum electrodynamic corrections, in the form of self-energy and vacuum polarization, are included. Another theoretical attempt, based on the Flexible Atomic Code, is presented for the atomic structure to serve as an independent check of the MCDF values and the results show fairly good agreement with the MCDF ones. Comparisons are made with available results in the literature. The uncertainties of our energies and strong transition rates are found to be approximately 0.25% and 2%, respectively. The extended and consistent data presented in this study should be of notable interest in various fusion research.

Here I present a fully ab initio time-resolved study of X-ray attosecond transient absorption spectroscopy (ATAS) in a prototypical polyatomic molecule, pyrazine, and demonstrate the possibility of retrieving the many-electron quantum ionic coherences arising in attosecond molecular photoionisation and pre-determining the subsequent charge-directed photochemical reactivity. Advanced first-principles many-electron simulations are performed, within a hybrid XUV pump/X-ray probe setup, to describe the interaction of pyrazine with both XUV pump and X-ray probe pulses, and study the triggered correlated many-electron dynamics. The calculations are carried out by means of the recently-developed ab initio method for many-electron dynamics in polyatomic molecules, the time-dependent (TD) B-spline Restricted Correlation Space-Algebraic Diagrammatic Construction (RCS-ADC). RCS-ADC simulates molecular ionisation from first principles, combining the accurate description of electron correlation of quantum chemistry with the full account of the continuum dynamics of the photoelectron. Complete theoretical characterisation of the atto-ionised many-electron state and photo-induced attosecond charge dynamics is achieved by calculating the reduced ionic density matrix (R-IDM) of the bipartite ion–photoelectron system, with full inclusion of the correlated shakeup states. Deviations from the sudden approximation picture of photoionisation, in the low-photon-energy limit, are presented. The effect of the multi-channel interaction between the parent-ion and the emitted photoelectron on the onset of the quantum electronic coherences is analysed. Moreover, I show how the Schmidt decomposition of the R-IDM unravels the many-electron dynamics triggered by the pump, allowing for the identification of the key channels involved. Finally, I calculate the X-ray attosecond transient absorption spectra of XUV-ionised pyrazine. The results unveil the mapping of the ATAS measurement onto the quantum electronic coherences, and related non-zero R-IDM matrix elements, produced upon ionisation by the XUV pump laser pulse.

High resolution jet-cooled spectroscopy experiments have been realized to investigate the intermolecular dynamics of van der Waals (vdW) heterodimers between NH3 and rare gas (Rg) atoms in the ν2 umbrella mode region of NH3. With respect to a previous study dedicated to NH3-Ar [Asselin et al. Mol. Phys. 116, 3642 (2018)], the sensitivity and spectral resolution of our laser spectrometer coupled to a pulsed supersonic jet have been significantly improved to derive more accurate excited state spectroscopic parameters from rovibrational analyses. In addition, we calculated the ground and ν2 excited vibration–rotation–tunneling (VRT) states of these complexes on the four-dimensional ab initio potential energy surfaces from Loreau et al. [J. Chem. Phys. 141, 224303 (2014), ibid. 143, 184303 (2015).] Transition frequencies and intensities of the allowed ν2 = 1 ← 0 transitions obtained from the calculated energy levels and wave functions agree well with the experimental data and are helpful in their analysis. By means of a pseudodiatomic model with the assumption of weak Coriolis coupling, the rovibrational analysis of both the Πe/f(j = 1,k = 0) ← Σf(j = 0,k = 0) and Σf(j = 1,k = 0) ← Σf(j = 0,k = 0) transitions in ortho NH3-Rg (Rg = Ne, Ar, Kr, Xe) complexes enabled us to determine reliable excited state parameters and derive accurate values of the effective vdW bond length Reff, force constant ks, and vdW stretching frequency νs. Comparison between the experimental structural parameters and those from the ab initio calculated VRT levels shows good agreement for NH3–Ne, NH3–Ar and NH3–Kr, and a similar variation of Reff, ks, and νs with the polarizability of Rg in the ground and ν2 excited states. Anomalously small values of νs and ks derived for NH3-Xe in the Πe/f(j = 1,k = 0) state suggest that the applied model is not valid in this case, due to the presence of another state coupling to the perturbed Πf state. Such a state could not be found, however.

The rate coefficients of rotationally inelastic collision processes for N2-HF as well as N2-DF systems were calculated by applying the recently developed coupled-states approximation including the nearest neighbor Coriolis couplings approach, based on the full-dimensional ab initio intermolecular potential energy surface. It was found that the energy gap law governs these energy transfer processes. For rotational quenching of N2 (j1 = 2-10) by the ground rotational state of HF, j1 = 6 and 5 have the maximum quenching rate for ortho-N2 and para-N2, respectively. Quenching rate coefficients for initially excited HF and DF (j2 = 1) in collisions with N2 were also reported, where N2-DF has a larger quenching rate than N2-HF due to larger density of states of the N2-DF system.

Scattering of thermal neutrons and Doppler broadening of epithermal neutron resonances in uranium and its compounds may be sensitive to crystal binding. The thermal scattering law (TSL) for uranium...

There is no doubt that electric fields of a specific frequency and intensity could excite certain vibrational modes of a macromolecule, which alters its mode coupling and conformation. Motivated by recent experiments and theories, we study the mode coupling between the Fe-CO mode and CO-stretch mode and vibration energy transfer among the active site and proteins in carboxyhemoglobin (HbCO) under different electric fields using the quasi-static two-dimensional infrared spectra. This study uses iron-porphyrin-imidazole-CO and two distal histidines in HbCO as the subsystem. The potential energy and dipole moment surfaces of the subsystem are calculated using an all-electron ab initio (B3LYP-D3(BJ)) method with the basis set Lanl2dz for the Fe atom and 6-31G(d,p) for C, H, O, and N atoms. Although the subsystem is reduced dimensionally, the anharmonic frequency and anharmonicity of the CO-stretch mode show excellent agreement with experimental values. We use the revealing noncovalent interaction method to confirm the hydrogen bond between the He atom of the His63 and the CO molecule. Our study confirms that the mode coupling between the Fe-CO mode and CO-stretch mode does not exist when the subsystem is free of electric field perturbation, which is coupled when the electric field is -0.5142 V/nm. In addition, with the increases of distance between the active site and the His92, there is no vibrational energy transfer between them when the electric field is 1.028 V/nm. We believe that our work could provide new ideas for increasing the dissociation efficiency of the Fe-CO bond and theoretical references for experimental research.

We developed a quantum-chemical approach for ab initio calculations of metastable-induced electron-emission spectra (MIES). In contrast to earlier work, our calculation method accounts for the anisotropy of the MIES spectra with respect to not only the direction of incidence of metastable helium but also to that of electron detection. Since we can freely choose both, incidence and detection direction in our simulation, our method is able to reconstruct MIES spectra which are dominated by Auger deexcitation for any experimental setups and orientation of the studied molecules. Here, we study the dependence of the MIES spectrum on the incidence and detection direction and other experimental parameters and compare the results for the case of adsorbed benzene with experimental data.

A new line list for hydronium (H316O+) is computed. The line list is based on a new ab initio dipole moment surface (CCSD(T)/aug-cc-pVQZ) and a new empirical potential energy surface (PES). The empirical PES of H3O+ was obtained by refining an ab initio surface through a global fit to the experimentally determined rovibrational energies collected from the literature covering the ground, $\nu _1^{\pm }$, $\nu _2^{\pm }$, $2\nu _2^{\pm }$, $\nu _3^{\pm }$, and $\nu _4^{\pm }$ vibrational states. The line list covers the wavenumber range up to 10 000 cm−1 (wavelengths $\gt 1 \, \mu$m) and should be complete for temperatures up to T = 1500 K. This is the first comprehensive line list for H3O+ with extensive wavenumber coverage and accurate transitional probabilities. Prospects of detection of hydronium in spectra of Solar system giant planets as well as exoplanets are discussed. The eXeL line list is publicly available from the ExoMol and CDS data bases.

The ion-pair states of IBr, ICl, and BrCl molecules correlating to the limits of dissociation X+(3P2,1,0, 1D2) + Y–(1S0) are studied using a complete active space self-consistent field (CASSCF), allowing for dynamic electronic correlations and spin–orbit interaction. Using experimental results, the calculated values of the equilibrium energy of the X+Y−(3P2) states correlating to the lowest ion state X+(3P2) are grouped in the range ΔTe ∼ 100 cm−1, with the error of their relative location also on the order of 100 cm−1. For most states, the difference between the experimental and calculated values of the equilibrium internuclear distance does not exceed $$R_{{\text{e}}}^{{\exp }}$$ – $$R_{{\text{e}}}^{{{\text{calc}}}}$$ = 0.02 A. A comparative analysis of structural features of the ion-pair states of homonuclear and heteronuclear halogen molecules is performed using results from recent ab initio calculations for the I2 molecule. We also discuss some issues concerning ion-pair states X−Y+ with inverted charge localization, which correlate to the limits of dissociation X– + Y+ and are coupled with the X+Y− states by two-electron transitions. It is noted that the structures with two stable localizations of two electrons, X+‒D‒Y− and X−‒D‒Y+, where X, Y are electron affinity centers (atoms, molecules, clusters) and D is a dielectric spacer, could be of interest for microelectronics.

Electronic transition dipoles are crucial for investigating light-matter interactions. Transition dipoles between metastable (autoionizing resonance) states become complex within non-Hermitian formalism, analogous to the resonance energies. Herein, we put forward a robust method for evaluating complex transition dipoles based on real ab initio stabilization calculations. The complex transition dipoles are obtained by analytical continuation via the Pade approximant and are identified as stationary solutions in the complex plane. The capability of the new approach is demonstrated for several transition dipoles of the doubly excited helium resonance states, for which exact values are available for comparison. Nevertheless, the method presented here has no inherent limitation and is suitable for polyatomic systems.

Collisions of the metastable antiprotonic helium atoms with the atoms of the medium cause, among other processes, transitions between hyperfine structure (HFS) states, as well as shifts and broadening of microwave M1 spectral lines. To obtain the interaction potential matrix ( $$\bar{p}$$ $$\bar{He}^{+}){-}\textrm{He}$$ , the potential energy surface (PES) is calculated by the unrestricted Hartree–Fock method with consideration of the electron correlations within the second-order of perturbation theory (MP2). With this potential, the system of equations of close coupling of the HFS channels is numerically solved; the cross sections and transition rates, shifts, and broadenings of M1 spectral lines are calculated; they are then used to solve the kinetic equation that determines the time evolution of the HFS state density matrix. The results of these calculations are compared with the experimental data and with the results of model calculations.

Fully Λ-doublet resolved differential cross sections and collision-induced rotational alignment moments have been measured for the NO(X)–Xe collision system at a collision energy of 519 cm−1 . The experiments combine initial quantum state selection, employing a hexapole inhomogeneous electric field, with quantum state resolved detection, using (1+1′ ) resonantly enhanced multiphoton ionization and velocity map ion imaging. The differential cross sections and polarization dependent differential cross sections are shown to agree well with quantum mechanical scattering calculations performed on ab initio potential energy surfaces [J. K los et al. J. Chem. Phys. 137, 014312 (2012)]. By comparison with quasi-classical trajectory calculations, quantum mechanical scattering calculations on a hard-shell potential, and kinematic apse model calculations, the effects of the attractive part of the potential on the measured differential cross sections and collision-induced rotational alignment moments are assessed.

The electronic stopping power is a fundamental quantity to many technological fields that use ion irradiation. Here we investigate the validity of using a fully ab initio computational scheme based on linear response time-dependent density functional theory to predict the random electronic stopping power (RESP) of a proton in bulk aluminum. We verify the power of using the extrapolation scheme to overcome the expected convergence issue of the RESP calculations. We show that the calculated RESP of valence electrons compares well with experimental data for low proton velocity only when at full convergence and including the exchange-correlation effect. We demonstrate that the inclusion of valence states only is sufficient for calculating the electronic stopping power up to the stopping maximum.

CH $_3$ internal rotation is one of the typical large amplitude motions in polyatomic molecules, the spectral analysis and theoretical calculations of which, were developed by Li-Hong Xu and Jon Hougen. We observed a Doppler-free high-resolution and high-precision spectrum of 9-methylanthracene (9MA) by using the collimated supersonic jet and optical frequency comb techniques. The potential energy curve of CH $_3$ internal rotation is expressed by a six-fold symmetric sinusoidal function. It was previously shown that the barrier height ( $V_6$ ) of 9MA- $d_{12}$ was considerably smaller than that of 9MA- $h_{12}$ [M. Baba, et al., J. Phys. Chem. A 113, 2366 (2009)]. We performed ab initio theoretical calculations of the multi-component molecular orbital method. The barrier reduction by deuterium substitution was partly attributed to the difference between the wave functions of H and D atomic nuclei.

A global potential energy surface for the lowest quartet state of HN2 is reported for the first time from accurate multi-reference ab initio calculations extrapolated to the complete basis set limit using the double many-body expansion method. All its stationary points are characterized, with the lowest quartet of HN2 predicted to have a bent global minimum 36 kcal mol-1 below the N(4S)+NH(X 3Σ−) asymptote, from which it is barrierlessly achievable. The entire set of calculated ab initio points has been fitted for energies up to 1000 kcal mol-1 above the global minimum with a rmsd of 0.89 kcal mol-1, a gap comprising all identified stationary points. Special care is taken in modeling the involved long-range for ces, and cusps caused by crossing seams. The novel PES will prompt for the calculation of rate constants for several unexplored reactions that are relevant for combustion, plasma and atmospheric chemistry.

We present and analyse a complete analytic expression for the generalized shielding polarizability third-rank tensor Φαβγ, whose isotropic average, the pseudoscalar [capital Phi, Greek, macron], is proportional to a chiral macroscopic electric polarization P measurable in a pulsed nuclear magnetic resonance (NMR) experiment probing molecules with an arbitrarily degenerate ground state, in solution. We have recently predicted that [capital Phi, Greek, macron] can be measurable at room temperature in chiral paramagnetic molecules, and identified strong magnetic anistropy (as featured e.g. in lanthanide complexes) as a crucial molecular property to achieve room temperature chiral discrimination using NMR spectroscopy. As previously proposed, the components of Φαβγ are obtained as analytical third derivatives of the electronic free energy. Here we present the explicit calculation of these derivatives, which provide working expressions for the explicit accurate ab initio calculation of Φαβγ. We apply our theory by performing ab initio multiconfigurational calculations of all contributions to Φαβγ, for a set of ten DyIII complexes, characterized by a strongly axial ground Kramers doublet, but also by thermally accessible excited Kramers doublets at room temperature. The results show that the thermally populated excited state contributions, while generally reducing the value of [capital Phi, Greek, macron] calculated on the assumption of a thermally isolated ground state, still confirm the room temperature detectability of this property for all ten studied complexes. Trends on the relative sign of dominant contributions are then discussed on the basis of a crystal field model electrostatic potential splitting a ground spin-orbit multiplet, which provides an insight into the properties of the generalized shielding polarizability tensor for open shell species.

In this study, the potential energy curves (PECs) and dipole moments for 1,3Σ+, 1,3Π and 1,3Δ states of the molecule FrCs and for 2Σ+, 2Π and 2Δ of (FrCs)+ have been computed using a quantum chemistry procedure. This method is based on pseudo-potentials for the representation of atomic core, effective core polarization potential, and large Gaussian basis sets. Besides, we have been deduced from these curves the vibrational levels and the spacing's for all symmetries. The (FrCs)+ and FrCs are modeled as one and two valence electrons, respectively and the Fr+ and Cs+ core are indicated by a pseudo-potential with middle relativistic effects together with the potential of effective core polarization. Since, no experimental results are available for these systems, we have compared our result with the theoretical result found by Aymar et al. and found a good agreement.

Explicit ab initio diabatic and adiabatic calculations of potential energy curves (PECs) of the states 1,3Σ+, 1,3Π, and 1,3Δ of francium hydride FrH have been carried out with several approaches. We determined for both representations the permanent and the transition dipole moment (PDM and TDM) and the vibrational levels. The calculation was based on the configuration interaction (CI) method, which includes effective core potentials (ECP) and core polarization potentials (CPP). The FrH system is considered as an effective two-electron system, permitting calculation of structural and electronic properties with full configuration interaction (FCI). For the diabatisation method, we perform an efficient diabatisation approach which depends on variational effective Hamiltonian theory (VEH) and a dynamic overlap matrix. This study complete the diabatic and adiabatic ab initio spectroscopic investigations of the series of all the alkali hydrides. In addition, we present our adiabatic results of FrH by comparing it with other alkali hydride systems (Li-Cs)H. This study is essential for a wide range of theoretical and experimental work.

The feasibility of laser cooling barium monohalides BaX (X = F, Cl, Br, I) is investigated using ab initio methods with the inclusion of spin–orbit coupling (SOC) effects. Calculated spectroscopic constants for BaF, BaCl, BaBr and BaI are in very good agreement with the available experimental measurements. The results demonstrate that the calculated electronic structure is accurate and can be used to establish the optical scheme of laser cooling. The highly diagonal Franck–Condon factors (FCFs) (BaF: f00 = 0.980, f11 = 0.939, f22 = 0.894; BaCl: f00 = 0.998, f11 = 0.995, f22 = 0.992) between the X2Σ+1/2 and A2Π1/2 states are determined, which are found to be in good agreement with previous theoretical results. The radiative lifetimes (BaF: 39.13–41.20 ns; BaCl: 117.99–110.23 ns) of the A2Π1/2–X2Σ+1/2 transition for the first five vibrational levels show that the A2Π1/2 is a rather short lifetime state. The current study indicates that BaF and BaCl are two good choices of molecules for laser cooling. Therefore, BaI and BaBr are not promising laser-cooling candidates because the FCFs of the A2Π1/2–X2Σ+1/2 transition are off-diagonal. We further propose the three-laser cooling schemes based on the A2Π1/2–X2Σ+1/2 transition for BaF and BaCl.

We performed high-level ab initio calculations on electronic structure of NaK. The potential energy curves (PECs) of 10 Λ-S states correlated with the three lowest dissociation limits have been calculated. On the basis of the calculated PECs, the spectroscopic constants of the bound??-S states are obtained, which are in good agreement with experimental results. The maximum vibrational quantum numbers of the singlet ground state X1Σ+ and the triplet ground state a3Σ+ have been analyzed with the semiclassical scattering theory. Transition properties including transition dipole moments, Franck-Condon factors, and radiative lifetimes have been investigated. The research results indicate that such calculations can provide fairly reliable estimation of parameters for the ultracold alkali diatomic molecular experiment.

Laser cooling of polyatomic molecules to the ultracold regime may enable some new science and technology applications; however, the related study is still at its very early stage. Here, by means of accurate ab initio and dynamical calculations, we identify two new candidate tetratomic molecules that are suitable for laser cooling and demonstrate the feasibility and advantage of two laser cooling schemes that are able to produce ultracold CaCCH and SrCCH molecules. The internally contracted multiconfiguration reference configuration interaction method is applied, and excellent agreement is achieved between the computed and experimental spectroscopic data. We find that the X2Σ1/2+→A2Π1/2 transitions for both candidates feature diagonal Franck–Condon factors, short radiative lifetimes, and no interference from intermediate electronic states. In addition, the crossings with higher electronic states do not interfere. We further construct feasible laser cooling schemes for CaCCH and SrCCH, each of which allows scattering 104 photons for direct laser cooling. The estimated Doppler temperatures for both CaCCH and SrCCH are on the order of μK.

We studied the directional dependency of electronic stopping power of swift light ions in nickel using real-time time-dependent density functional theory. We report a variation of electronic stopping for moving ions as the projectile probes different electronic densities of the host material. These results show that while the predicted magnitude stays in reasonable agreement with experiment, for $$v > 2$$ v > 2 . a.u. simulating only low index crystallographic directions is not enough to sample the experimental average values. The ab initio simulations give us access to microscopic quantities, such as non-adiabatic forces, momentum transfer and transient excited state charges of the projectile and host ions, which are not available through other methods. We report these quantities for the first time.

Relative phases of atomic above-threshold ionization wave packets were investigated in an experiment [L. J. Zipp, A. Natan, and P. H. Bucksbaum, Optica 1, 361 (2014)] exploiting interferences between different pathways in a weak probe field at half the frequency of the strong ionization pulse. In this work we explore theoretically the extraction of phase delays and time delays of attosecond wave packets formed in strong-field ionization. We perform simulations solving the time-dependent Schr\"odinger equation and compare these results with the strong-field and Coulomb-Volkov approximations. In order to disentangle short- from long-range effects of the atomic potential, we also perform simulations for atomic model potentials featuring a Yukawa-type short-range potential. We find significant deviations of the ab initio phase delays between different photoelectron pathways from the predictions by the strong-field approximation even at energies well above the ionization threshold. We identify similarities to but also profound differences from the well-known interferometric extraction of phase and time delays in one-photon ionization.

The energies and decay widths of the states of the exotic $^{7}\mathrm{He}$ nucleus are studied in an ab initio approach. The spectrum of these states is calculated using the no-core shell model (NCSM) and a corresponding extrapolation procedure. The Daejeon16 potential, well proved on a large amount of data, is used in the calculations. The previously developed NCSM-based approach, which includes a method for constructing the basis of functions of cluster channels and a procedure for matching the cluster form factors obtained within this method with the corresponding asymptotic wave functions, is applied to compute the decay widths of the levels. The possibilities of the approach are demonstrated for calculating the partial decay widths of nuclear states into various channels that strongly differ in type of fragmentation, spin, angular momentum of relative motion, and amplitude. The results obtained are compared with the results of other microscopic calculations.

We reinvestigate a key process in electron-atom collision physics, the elastic scattering of electrons from helium atoms. Specifically, results from a special-purpose relativistic polarized-orbital method, which is designed to treat elastic scattering only, are compared with those from a very extensive, fully ab initio, general-purpose B-spline R-matrix (close-coupling) code.

Our gargantuan ab initio all-electron fully relativistic Dirac–Fock (DF), nonrelativistic (NR) Hartree–Fock (HF) and Dirac–Fock-Breit-Gaunt (DFBG) molecular SCF calculations for the superheavy octahedral oganesson hexatenniside OgTs6 predict atomization energies (AEs) of 9.49, −5.54 and 9.37 eV, at the optimized Og-Ts bond distances of 3.35, 3.44 and 3.36 A, respectively. There are dramatic effects of relativity for the atomization energy for OgTs6 (with seven superheavy atoms and 820 electrons) of ~15.0 eV at both the DF and DFBG levels of theory. Our calculated energies of reaction for the superheavy reaction Og + 3Ts2 → OgTs6 at the NR, DF and DFBG levels of the theory are exoergic by 8.81, 6.33 and 6.26 eV, respectively. The contribution to dispersion interactions increases the DFBG reaction energy for Og + 3Ts2 → OgTs6 by 0.94–7.20 eV. The AEs of OgTs6 to form Og + 6Ts are calculated to be −5.54 at the NR level of theory (that is, OgTs6 is unstable relative to the sum of the NR energies of its constituent atoms) and 9.49 and 9.37 eV at the DF and DFBG levels of theory, respectively. Dispersion interactions increase the AE(DFBG) by 1.30–10.67 eV. Ours are the first dispersion interaction corrected calculations for OgTs6 with seven superheavy atoms and 820 electrons. Mulliken population analysis (MPA) as implemented in the DIRAC code for our DF and NR calculations (using the dyall.cv4z basis) yields the charges Og+0.60 and Og+0.96, respectively, on the central Og atom indicating that our relativistic DF calculations predict octahedral OgTs6 to be less ionic compared to our NR HF calculations. However, due caution must be used to interpret the results of MPA, which are highly basis set dependent.

The analysis of the vacuum spark spectrum of erbium in the wavelength region 705 - 2460 A has been extended. A total of 1022 spectral lines are newly identified as transitions between the low lying configurations 4 f 11 , 4 f 10 5 d , 4 f 10 6 s and 4 f 10 6 p of the Er 3 + ion (Er IV), in addition to the confirmed previously identified 582 ones. The extended analysis has led to the determination of 168 new energy levels in Er 3 + , in addition to the 120 previously known ones. Energy values have been optimised by a least-squares procedure based on an increased number of measured wavelengths, resulting in a reduction of their uncertainties. Parametric calculations have been performed using the Cowan codes, in which radial integrals are parameters fitted by least-squares minimisation of the differences calculated - experimental energies. The increased number of experimentally known levels leads to better defined parameters and improved predictions of unknown energy levels and electric dipole transition probabilities. Fitted parameters are compared with ab initio Hartree-Fock integrals including relativistic corrections (HFR). The mean errors of the fits are respectively 51 cm − 1 for 65 known levels of the odd configurations 4 f 11 + 4 f 10 6 p with 9 free parameters, and 53 cm − 1 for 223 known levels of the even configurations 4 f 10 5 d + 4 f 10 6 s with 17 free parameters.

We present an ab initio derivation method for effective low-energy Hamiltonians of material with strong spin-orbit interactions. The effective Hamiltonian is described in terms of the Wannier function in the spinor form, and effective interactions are derived with the constrained random phase approximation (cRPA) method. Based on this formalism and the developed code, we derive an effective Hamiltonian of a strong spin-orbit interaction material ${\mathrm{Ca}}_{5}{\mathrm{Ir}}_{3}{\mathrm{O}}_{12}$. This system consists of three edge-shared ${\mathrm{IrO}}_{6}$ octahedral chains arranged along the $c$ axis, and the three Ir atoms in the $ab$ plane compose a triangular lattice. For such a complicated structure, we need to set up the Wannier spinor function under the local coordinate system. We found that a density-functional band structure near the Fermi level is formed by local ${d}_{xy}$ and ${d}_{yz}$ orbitals. Then, we constructed the ab initio ${d}_{xy}/{d}_{yz}$ model. The estimated nearest-neighbor transfer $t$ is close to 0.2 eV, and the cRPA on-site $U$ and neighboring $V$ electronic interactions are found to be 2.4--2.5 eV and 1 eV, respectively. The resulting characteristic correlation strength defined by $(U\ensuremath{-}V)/t$ is above 7, and thus this material is classified as a strongly correlated electron system. The on-site transfer integral involved in the spin-orbit interaction is 0.2 eV, which is comparable to the on-site exchange integrals $\ensuremath{\sim}0.2$ eV, indicating that the spin-orbit-interaction physics would compete with the Hund physics. Based on these calculated results, we discuss possible rich ground-state low-energy electronic structures of spin, charge, and orbitals with competing Hund, spin-orbit, and strong-correlation physics.

Electron—core hole interactions are critical for proper interpretation of core-level spectroscopies commonly used as analytical tools in materials science. Here we utilize resonant Auger-electron spectroscopy to uniquely identify exciton, shake, and charge-transfer processes that result from the sudden creation of the core hole in both x-ray-absorption and photoemission spectra. These effects are captured for the transition-metal compounds SrTiO(3) and MoS(2) by fully ab initio, combined real-time cumulant, and Bethe-Salpeter equation approaches to account for core hole dynamics and screening. Atomic charges and excited-state electron-density fluctuations reflect materials’ solid-state electronic structure, loss of translational symmetry around the core hole, and breakdown of the sudden approximation. They also demonstrate competition between long- and short-range screening in a solid.

The cross sections and rate coefficients for the inelastic processes of mutual neutralization, ion-pair formation, and (de)-excitation in lithium-hydrogen collisions are calculated based on the ab initio electronic structure [J. Phys. B: At. Mol. Opt. Phys. 32, 81 (1999)] and the hopping probability current method [Phys. Rev. A 88, 052704 (2013)] for the nonadiabatic nuclear dynamics. For each given set of collisional parameters, calculations of the probability current evolution were repeated $2.621\phantom{\rule{0.16em}{0ex}}44\ifmmode\times\else\texttimes\fi{}{10}^{9}$ times, and this leads to a high accuracy of the inelastic state-to-state transition probabilities, the cross sections, and finally, the rate coefficients. The isotopic effects on the processes in collisions $^{6}\mathrm{Li}/^{7}\mathrm{Li}+\mathrm{H}/\mathrm{D}/\mathrm{T}$, where (H/D/T) represents hydrogen, deuterium, and tritium, for different isotopes are studied. In addition, the deexcitation resonance processes $^{6,7}\mathrm{Li}(2p\ensuremath{\rightarrow}2s)+\mathrm{H}/\mathrm{D}/\mathrm{T}$ were treated by the branching probability current method. It is found that the isotopic effects are different for different collisional partners and for different electronic states involved into a process, varying from negligible effects for high-lying Li states to strong effects for low-lying Li states. The resonance transition process is one with the strongest isotopic effects: replacing H by T changes the rate coefficient by up to four orders of magnitude. Unfortunately, there is no experimental data for the processes with strong isotropic effects, only for the processes with moderate effects, up to 60%.

The $A=4$ nuclei, i.e., $^{4}\mathrm{H}, ^{4}\mathrm{He}$, and $^{4}\mathrm{Li}$, establish an interesting isospin $T=1$ isobaric system. $^{4}\mathrm{H}$ and $^{4}\mathrm{Li}$ are unbound broad resonances, whereas $^{4}\mathrm{He}$ is deeply bound in its ground state but unbound in all its excited states. The present situation is that experiments so far have not given consistent data on the resonances. Few-body calculations have well studied the scatterings of the $4N$ systems. In the present work, we provide many-body calculations of the broad resonance structures, in an ab initio framework with modern realistic interactions. It occurs that, indeed, $^{4}\mathrm{H}, ^{4}\mathrm{Li}$, and excited $^{4}\mathrm{He}$ are broad resonances, which is in accordance with experimental observations. The calculations also show that the first ${1}^{\ensuremath{-}}$ excited state almost degenerates with the ${2}^{\ensuremath{-}}$ ground state in the pair of mirror isobars of $^{4}\mathrm{H}$ and $^{4}\mathrm{Li}$, which may suggest that the experimental data on energy and width are the mixture of the ground state and the first excited state. The $T=1$ isospin triplet formed with an excited state of $^{4}\mathrm{He}$ and ground states of $^{4}\mathrm{H}$ and $^{4}\mathrm{Li}$ is studied, focusing on the effect of isospin symmetry breaking.

The $\ensuremath{\beta}$ decay of the isomeric and ground state of $^{50}\mathrm{Sc}$ to the semimagic nucleus $_{22}^{50}\mathrm{Ti}_{28}$ has been studied using a $^{50}\mathrm{Ca}$ beam delivered to the GRIFFIN $\ensuremath{\gamma}$-ray spectrometer at the TRIUMF-ISAC facility. $\ensuremath{\beta}$-decay branching ratios are reported to 16 excited states with a total of 38 $\ensuremath{\gamma}$-ray transitions linking them. These new data significantly expand the information available over previous studies. Relative intensities are measured to less than 0.001 $%$ that of the strongest transition with the majority of $\ensuremath{\gamma}$-ray transitions observed here in $\ensuremath{\beta}$ decay for the first time. The data are compared with shell-model calculations utilizing both phenomenologically derived interactions employed in the $pf$ shell as well as a state-of-the-art ab initio-based interaction built in the valence-space in-medium similarity renormalization-group framework.

A very accurate, (HF)$_2$ potential energy surface (PES) due to Huang et al. (J. Chem. Phys., 150, 154302 (2019)) is used to calculate the energy levels of the HF dimer by solving the nuclear-motion Schr\"{o}dinger equation using variational program WAVR4. Calculations on an extended range of rotational states show very good agreement with experimental data. In particular the known empirical rotational constants for the ground and some observed excited vibrational states are reproduced with an accuracy of about 50 MHz. This level of accuracy is shown to extend to higher excited inter-molecular vibrational states $v$ and higher excited rotational quantum numbers $(J,K_a)$. These calculations allow the assignment of 3 new $J$-branches in an HF dimer tunneling-rotation spectra recorded 30 years ago. These branches belong to excited $K_a$ = 4 state of the ground vibrational state, and $K_a$ = 0 states of excited inter-molecular vibrational states., Comment: arXiv admin note: substantial text overlap with arXiv:2107.05969

By ab-initio methods, the spectroscopy of lanthanum hydride molecule LaH is predicted and the states involved in all the observed band systems are assigned. So, 34 low - lying 1,3Λ(±) states located below 31400 cm−1 are calculated and 67 Ω(±) states are generated by taking into account the spin–orbit coupling effect of lanthanum. For these states, the spectroscopic constants such as R e , T e , ω e and ω e χ e are determined and the potential energy curves (PECs) are plotted in the range of internuclear distance from 1.00 A to 3.00 A. The calculated electronic configuration of 1,3Λ(±) states shows the ionic nature La+H- of this species. Moreover, the composition of the Ω(±) state-wave functions in term of Λ-S parent states are calculated at the equilibrium internuclear distance of the ground state. Indeed, this molecule belongs to Hund’s case (c) since the transition in many observed band systems only obeys the rule ΔΩ = 0, ±1.

We report multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction calculations on the thallium (Tl) electron affinity, as well as on the excited energy levels arising from the ground configuration of ${\mathrm{Tl}}^{\ensuremath{-}}$. The results are compared with the available experimental values and further validated by extending the study to its homologous, lighter element, indium (In), belonging to group 13 (III.A) of the Periodic Table. The calculated electron affinities of In and Tl, 383.4 and 322.8 meV, agree with the latest measurements by within 1%. Three bound states ${}^{3}{P}_{0,1,2}$ are confirmed in the $5{s}^{2}5{p}^{2}$ configuration of ${\mathrm{In}}^{\ensuremath{-}}$, while only the ground state ${}^{3}{P}_{0}$ is bound in the $6{s}^{2}6{p}^{2}$ configuration of ${\mathrm{Tl}}^{\ensuremath{-}}$. The isotope shifts on the In and Tl electron affinities are also estimated. The E2 and M1 intraconfiguration radiative transition rates within $5{s}^{2}5{p}^{2} {}^{3}{P}_{0,1,2}$ of ${\mathrm{In}}^{\ensuremath{-}}$ are used to calculate the radiative lifetimes of the metastable ${}^{3}{P}_{1,2}$ levels.

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.

When we theoretically investigate interaction of an intense and ultrashort laser pulse with solids, there are two aspects that should be considered: the strong electric field of the light pulse induces extremely nonlinear electron dynamics in solids that cannot be described by perturbation theory. The nonlinear electron dynamics manifests as a nonlinear polarization in macroscopic scale that determines the propagation of the light pulse. Therefore, to describe the propagation of the intense light pulse, it is necessary to treat the coupled dynamics of the light electromagnetic fields and the electron dynamics. The scheme should also take into account the separation of the spatial scale of two dynamics. We have developed a theoretical and computational approach based on ab initio time-dependent density functional theory for interaction of strong and ultrashort laser pulse with solids and have applied the method to various phenomena. In my presentation, I will show our recent progresses of ab initio simulation in nano-optics.

The GYT line list covering rotational, rovibrational and rovibronic transitions of the mercapto radical SH is presented. This work extends and replaces the SNaSH line list [Yurchenko et al., 2018, MNRAS, 478, 270] which covers the ground (electronic) $X$ $^{2}\Pi$ state only. This extension is prompted by the tentative identification of the ultra-violet features of SH as being of importance in the transmission spectrum of the ultra-hot Jupiter exoplanet WASP-121b [Evans et al., 2018, AJ., 156, 283]. This GYT line list model is generated by fitting empirical potential energy, spin-orbit and electronic angular momenta functions to experimentally measured wavelengths within the $X$ $^{2}\Pi$ and $A$ $^{2}\Sigma^{+}$ states and to the $A$ $^{2}\Sigma^{+}$ - $X$ $^{2}\Pi$ band system using ab initio curves as a starting reference point. The fits are compatible with the quoted uncertainty of the experimental data used of $\sim$ 0.03 - 0.3 cm$^{-1}$. The GYT line list covers wavelengths longer than 0.256 $\mu$m and includes 7686 rovibronic states and 572 145 transitions for $^{32}$SH. Line lists for the $^{33}$SH, $^{34}$SH, $^{36}$SH and $^{32}$SD isotopologues are generated including a consideration of non-Born-Oppenheimer effects for SD. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.