Low-lying Doublet Research Articles

The low-lying doublet electronic excited states of ZrO2−: A symmetry adapted cluster–configuration interaction (SAC-CI) study

The low-lying doublet excited states of ZrO2− were studied using the SAC-CI method. The vertical excitation spectrum of ZrO2− was calculated and compared with that of TiO2−. Similar to that for TiO2−, ZrO2− also have a dipole-bound state. The ground electronic state (X2A1) and the excited states having bound characters (22A1, 12B1, and dipole-bound states) were optimized to C2v structures. The adiabatic electronic affinity of ZrO2 and the adiabatic excitation energies of the three bound excited states were obtained at the SAC-CI level.

Theoretical electronic structure with dipole moment and rovibrational calculation of the low-lying electronic states of the HgF molecule

With the lack of evitable data about the electronic structure of the low-lying states of the HgF molecule unlike its counter parts of mercury monohalides, spectroscopic study of eighteen low-lying doublet and quartet electronic states in the representation 2s+1Λ(+\\-) of this molecule is conducted. Adiabatic potential energy curves of those states are investigated using the complete active space self consistent field (CASSCF) calculation with multi-reference configuration interaction (MRCI) method including single and double excitations with Davidson correction (+Q). The spectroscopic constants as Re, ωe, ωexe, Be, αe, Te and μe are calculated for the bound states. The dissociation energy D00 and the percentage ionic character fionic are also computed. The transition dipole moment μTDM between some doublet low-lying states is studied and some emission coefficients as the Einstein spontaneous coefficients A21, the spontaneous radiative lifetime τspon, and the oscillator strength f21 are thus determined. A rovibrational study has been done to investigate the vibrational levels of the low-lying bound states and the vibrational constants Ev, Bv, Dv, Rmin and Rmax are reported. The Franck–Condon factors have also been calculated for the most probable transitions between the excited states and the ground state. The comparison between the values of the present work and those short information available in the literature shows good accordance.

Theoretical electronic structure of the molecule SrCl for the feasibility of laser cooling

Electronic structure of the molecule SrCl has been investigated by employing the ab initio methods CASSCF/MRCI+Q with Davidson correction in the representation 2s+1Λ±, neglecting spin-orbit effects, and using the computational program Molpro. The potential energy curves of the low-lying doublet and quartet electronic states have been investigated. The harmonic vibrational wave number ωe, the relative electronic energy Te, referred to the ground state, the rotational constant Be and the equilibrium internuclear distance Re, have been calculated for the investigated electronic states. Moreover, the static dipolar moments have been determined in term of the internuclear distance Re.

The low-lying doublet electronic excited states of TiO2−: A symmetry adapted cluster–configuration interaction (SAC-CI) study

The low-lying doublet excited states of the singly charged TiO2 anion (TiO2−) were investigated by the SAC-CI method. The vertical excitation spectrum of TiO2− was calculated at the SAC-CI/aug-cc-pVTZ levels. The ground electronic state (X2A1) and the lowest two valence excited states (22A1 and 12B1) having bound characters were optimized to stable C2v structures. A dipole-bound state (2A1) was found and optimized to a C2v structure. The adiabatic energies of the 22A1, 12B1, and dipole-bound states were obtained.

Magnetic structure of DyN: A Dy161 Mössbauer study

Conventional magnetometry yields a low temperature bulk magnetic moment of about $4\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/\phantom{{\ensuremath{\mu}}_{\mathrm{B}}\mathrm{D}{\mathrm{y}}^{3+}}\phantom{\rule{0.0pt}{0ex}}\mathrm{D}{\mathrm{y}}^{3+}$ in an applied field of ${\ensuremath{\mu}}_{0}H=9\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ for thin and thick dysprosium nitride (DyN) films. This is significantly lower than the maximum possible value of $10\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/\phantom{10\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}\mathrm{D}{\mathrm{y}}^{3+}}\phantom{\rule{0.0pt}{0ex}}\mathrm{D}{\mathrm{y}}^{3+}.$ Ion-assisted deposition was used to grow 5.7-\ensuremath{\mu}m-thick rare earth nitride DyN films on organic Kapton\textregistered{} substrates. $^{161}\mathrm{Dy}$ M\ossbauer spectroscopy (with its time scale on the order of nanoseconds) indicates thermal relaxation between fully stretched $\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$ levels of a low-lying Kramers doublet, which is inconsistent with the $\mathrm{D}{\mathrm{y}}^{3+}$ site's ideal cubic symmetry. However, a small tetragonal distortion $[\ensuremath{\epsilon}\ensuremath{\approx}\ensuremath{-}0.024(10)]$ observed using x-ray powder diffraction is compatible with an additional rank 2 crystal field term, ${B}_{2}^{0}\ensuremath{\approx}\ensuremath{-}1.0(4)\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, approaching the magnitude estimated to bring this about. The observed magnetic behavior can then be described using a two-level, molecular field model with ${\ensuremath{\theta}}_{\mathrm{C}}$ set to $\ensuremath{\approx}6--8\phantom{\rule{0.16em}{0ex}}\mathrm{K},$ which is substantially smaller than the accepted ordering temperature of ${T}_{\mathrm{C}}\ensuremath{\approx}17--26\phantom{\rule{0.16em}{0ex}}\mathrm{K}$.

Electronic structure with dipole moment and ionicity calculations of the low-lying electronic states of the ZnF molecule

Adiabatic potential energy curves of the 28 low-lying doublet and quartet electronic states in the representation 2s+1Λ(±) of the zinc monofluoride molecule are investigated using the complete active space self-consistent field (CASSCF) with multi-reference configuration interaction (MRCI) method including single and double excitations with the Davidson correction (+Q). The internuclear distance Re, the harmonic frequency ωe, the static and transition dipole moment μ, the rotational constant Be, and the electronic transition energy with respect to the ground state Te are calculated for the bound states. The transition dipole moment between some doublet states is used to determine the Einstein spontaneous A21 and induced emission [Formula: see text] coefficients, as well as the spontaneous radiative lifetime τspon, emission wavelength λ21, and oscillator strength f21. The ground state ionicity qionicity and equilibrium dissociation energy DE,e are also computed. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Twenty-three new electronic states have been studied in the present work for the first time.

Single-Molecule Magnet Properties of Transition-Metal Ions Encapsulated in Lacunary Polyoxometalates: A Theoretical Study.

Single-molecule magnet (SMM) properties of transition-metal complexes coordinated to lacunary polyoxometalates (POM) are studied by means of state of the art ab initio methodology. Three [M(γ-SiW10O36)2] (M = Mn(III), Fe(III), Co(II)) complexes synthesized by Sato et al. (Chem. Commun. 2015, 51, 4081-4084) are analyzed in detail. SMM properties for the Co(II) and Mn(III) systems can be rationalized due to the presence of low-energy excitations in the case of Co(II), which are much higher in energy in the case of Mn(III). The magnetic behavior of both cases is consistent with simple d-orbital splitting considerations. The case of the Fe(III) complex is special, as it presents a sizable demagnetization barrier for a high-spin d(5) configuration, which should be magnetically isotropic. We conclude that a plausible explanation for this behavior is related to the presence of low-lying quartet and doublet states from the iron(III) center. This scenario is supported by ab initio ligand field analysis based on complete active space self-consistent field results, which picture a d-orbital splitting that resembles more a square-planar geometry than an octahedral one, stabilizing lower multiplicity states. This coordination environment is sustained by the rigidity of the POM ligand, which imposes a longer axial bond distance to the inner oxygen atom in comparison to the more external, equatorial donor atoms.

Deciphering the origin of giant magnetic anisotropy and fast quantum tunnelling in Rhenium(IV) single-molecule magnets.

Single-molecule magnets represent a promising route to achieve potential applications such as high-density information storage and spintronics devices. Among others, 4d/5d elements such as Re(IV) ion are found to exhibit very large magnetic anisotropy, and inclusion of this ion-aggregated clusters yields several attractive molecular magnets. Here, using ab intio calculations, we unravel the source of giant magnetic anisotropy associated with the Re(IV) ions by studying a series of mononuclear Re(IV) six coordinate complexes. The low-lying doublet states are found to be responsible for large magnetic anisotropy and the sign of the axial zero-field splitting parameter (D) can be categorically predicted based on the position of the ligand coordination. Large transverse anisotropy along with large hyperfine interactions opens up multiple relaxation channels leading to a fast quantum tunnelling of the magnetization (QTM) process. Enhancing the Re-ligand covalency is found to significantly quench the QTM process.

Mössbauer spectroscopy, magnetization, magnetic susceptibility, and low temperature heat capacity of α-Na2NpO4

The physical and chemical properties at low temperatures of hexavalent disodium neptunate α-Na2NpO4 are investigated for the first time in this work using Mössbauer spectroscopy, magnetization, magnetic susceptibility, and heat capacity measurements. The Np(VI) valence state is confirmed by the isomer shift value of the Mössbauer spectra, and the local structural environment around the neptunium cation is related to the fitted quadrupole coupling constant and asymmetry parameters. Moreover, magnetic hyperfine splitting is reported below 12.5 K, which could indicate magnetic ordering at this temperature. This interpretation is further substantiated by the existence of a λ-peak at 12.5 K in the heat capacity curve, which is shifted to lower temperatures with the application of a magnetic field, suggesting antiferromagnetic ordering. However, the absence of any anomaly in the magnetization and magnetic susceptibility data shows that the observed transition is more intricate. In addition, the heat capacity measurements suggest the existence of a Schottky-type anomaly above 15 K associated with a low-lying electronic doublet found about 60 cm−1 above the ground state doublet. The possibility of a quadrupolar transition associated with a ground state pseudoquartet is thereafter discussed. The present results finally bring new insights into the complex magnetic and electronic peculiarities of α-Na2NpO4.

Ab initio study of the low-lying electronic states of the [formula omitted] anion

Six low-lying states (X2Σg+, A2Πu, B2Σu+, 4Σg+, 4Πu and 4Σu+) of C2− anion are studied by highly correlated ab initio calculations. The potential energy curves (PECs) are computed in the internuclear separation from 0.8 to 5.0Å using the complete active space self-consistent field method, and then performing the internally contracted multireference configuration interaction with Davidson correction. Core–valence correlation and scalar relativistic effect are considered through employing the aug-cc-pcV5Z-dk basis set. The spin–orbit coupling of the A2Πu state is also calculated using Breit–Pauli Hamiltonian. Based on the PECs derived from the high-level ab initio calculations, the spectroscopic parameters are obtained by fitting the ro-vibrational levels that are acquired by solving the ro-vibrational Schrödinger equation. These spectroscopic parameters, especially for low-lying doublet states, are in good agreement with the previously calculated and experimental results. Finally, the electronic transition dipole moment matrix elements, Franck–Condon factors, radiative lifetimes and oscillator strengths of A2Πu–X2Σg+andB2Σu+-X2Σg+ are calculated and discussed as well.

The suitability of barium monofluoride for laser cooling from ab initio study

ABSTRACTThe feasibility of laser cooling the 138Ba19F molecule is performed using ab initio quantum chemistry. Three low-lying doublet electronic states X 2Σ+, A' 2Δ and A 2Π are determined by the multireference configuration-interaction (MRCI) method, where the spin–orbit coupling (SOC) effect is also taken into account in the electronic structure calculations. The computed spectroscopic constants and permanent dipole moments agree well with the available experimental data. The Franck–Condon factors of the A 2П → X 2Σ+ transition show highly diagonal dominance (f00 = 0.981, f11 = 0.940, f22 = 0.896) and the A 2П state has a radiative lifetime of τ = 37.8 ns, allowing for rapid laser cooling. Our calculation indicates that the laser-cooling scheme require only three lasers at 822 nm, 855 nm and 856 nm proceeded on the A 2П (ν′) ← X 2Σ+ (ν′′) transitions. The appeared intervening state A' 2Δ between the X 2Σ+ and A 2П states is the main challenge for laser cooling this molecule. In fact, the calculated vibrational branching loss ratio to the intermediate A' 2Δ state is almost negligible at a level of η < 4.5 × 10−9. Thus, BaF is a promising laser-cooling candidate with a relatively simple laser-cooling scheme.

Electronic structure with dipole moment calculation of the low-lying electronic states of ZnBr molecule

Adiabatic potential energy curves of 19 low-lying doublet and quartet electronic states in the representation 2s+1Λ(±) of the zinc mono-bromide molecule ZnBr are investigated using high correlated ab initio calculations. For the bound states, the equilibrium internuclear distance Re, the harmonic frequency ωe, the rotational constant Be and the electronic transition energy with respect to the ground state Te have been calculated at the multireference configuration interaction (MRCI) level including single and double excitations with Davidson correction (+Q). Sixteen low-lying states are presented here for the first time. The ground state dissociation energy is also calculated. The comparison between the values of the present work are in agreement with those available in the literature.

Ab initio calculations of the electronic structure of the low-lying states for the ultracold LiYb molecule.

Ab initio techniques have been applied to investigate the electronic structure of the LiYb molecule. The potential energy curves have been computed in the Born-Oppenheimer approximation for the ground and 29 low-lying doublet and quartet excited electronic states. Complete active space self-consistent field, multi-reference configuration interaction, and Rayleigh Schrödinger perturbation theory to second order calculations have been utilized to investigate these states. The spectroscopic constants, ωe, Re, Be, …, and the static dipole moment, μ, have been investigated by using the two different techniques of calculation with five different types of basis. The eigenvalues, Ev, the rotational constant, Bv, the centrifugal distortion constant, Dv, and the abscissas of the turning points, Rmin and Rmax, have been calculated by using the canonical functions approach. The comparison between the values of the present work, calculated by different techniques, and those available in the literature for several electronic states shows a very good agreement. Twenty-one new electronic states have been studied here for the first time.

Development of 3He insert for Magnetization Measurements down to T = 0.4 K with SQUID magnetometer

We have developed a 9-mm-diameter 3He insert for precise magnetization measurements down to T = 0.4 K that is attachable to a commercial superconducting quantum interference device magnetometer. The insert is made from a thin-walled stainless steel pipe with an inner diameter of 6.2 mm, which determines the maximum sample size. 3He gas is condensed in the pipe, which is liquefied by 4He gas at T = 1.8 K generated by the magnetometer via the heat exchanger of a Cu vacuum jacket with an outer diameter of 8.6mm soldered to the stainless steel pipe. The temperature of the insert is decreased to T = 0.5 K by evacuating liquid 3He using a rotary pump and then to T = 0.36 K with a sorption pump. From the diamagnetization signal of a superconducting Al chip with a mass below 0.1 mg, the magnetization resolution with the insert is confirmed to be less than 10−7 emu. We measure the temperature dependence of magnetization down to T = 0.5 K in PrxLa1-xPb3, which is a good candidate for the reality of the quadrupolar Kondo effect, using the 3He insert. Non-Fermi liquid behavior of the nonlinear susceptibility in χ3 with a -lnT dependence is detected in the [100] and [110] directions below T = 2.5 K, suggesting the screening of quadrupolar moments. In contrast, χ3 in the [111] direction becomes constant below T = 3 K. The observed features indicate that a low-lying Γ3 doublet plays a crucial role in the anomalous properties of PrxLa1-xPb3.

&amp;lt;i&amp;gt;Ab-Initio&amp;lt;/i&amp;gt; Calculations of 27 Electronic States of the BP&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; Ion-Molecule

The theoretical investigation of the potential energy curves, in the representation 2s+1Λ(+/-), of the 27 low-lying Doublet and Quartet electronic states of the BP+ molecular ion has been performed with the methods in quantum chemistry, the Complete Active Space Self Consistent Field (CASSCF) and the Multireference Configuration Interaction (MRCI) calculations. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have also been calculated. Twenty-three new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. These investigated data can be a conducive to further work on BP+ molecular ion in both experimental and theoretical research.

Theoretical calculation of the low-lying doublet electronic states of the SrF molecule

The potential energy curves of the low-lying doublet electronic states in the representation 2s+1Λ(+/−) of the SrF molecule have been investigated by using the complete active space self-consistent field with multireference configuration interaction and multireference Rayleigh–Schrödinger perturbation theory methods. The harmonic frequency, ωe; the internuclear distance, Re; the dipole moment; and the electronic energy with respect to the ground state, Te, have been calculated for the considered electronic states. The eigenvalues, Ev; the rotational constants, Bv; and the abscissas of the turning points, Rmin and Rmax, have been investigated using the canonical functions approach. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Nine new electronic states have been investigated here for the first time.

Discrete trinuclear copper(II) compounds as building blocks: the influence of the peripheral substituents on the magnetic coupling in oxamato-bridged complexes.

Two new trinuclear copper(ii) complexes without end-capping ligands, (Bu4N)2[Cu(dmso)2{Cu(dnopba)(dmso)}2] () and (Bu4N)2[Cu(dmso)2{Cu(dcopba)(dmso)}2] () [dnopba = 4,5-dinitro-ortho-phenylenebis(oxamate), dcopba = 4,5-dichloro-ortho-phenylenebis(oxamate), Bu4N(+) = tetra-n-butylammonium and dmso = dimethylsulfoxide], were synthesized and their structures were determined by single crystal X-ray diffraction. The crystal structures of and consist of two outer bis(oxamato)(dmso)cuprate(ii) units which act as bidentate ligands toward a trans-bis(dmso)copper(ii) inner entity leading to centrosymmetric tricopper(ii) complexes with copper-copper separations across the oxamate bridges of 5.1916(3) () and 5.1776(3) Å (). The peripheral copper(ii) ions in and are five-coordinate in somewhat distorted square pyramidal environments with a dmso molecule filling the apical position whereas the inner copper(ii) ion is six-coordinate in an elongated octahedral environment with two dmso molecules in the axial sites. The investigation of their magnetic properties in the temperature range 2.0-300 K shows the occurrence of a strong intramolecular antiferromagnetic coupling between the copper(ii) ions through the oxamate bridges [J1 = -296(1) () and -334(1) cm(-1) (), the Hamiltonian being defined as Ĥ = -J1(ŜCu2·ŜCu1 + ŜCu2·ŜCu1')], which leads to a low-lying spin doublet at low temperatures. Density functional theory calculations (DFT) have been used to substantiate these magnetic couplings and also to analyse the influence exerted on these interactions by the type of substituent at the 4,5-positions from the phenylene ring of the bis(oxamate) ligand.

Nonlinear Susceptibility Measurement for Quadrupolar Response in a Dilute Γ3Non-Kramers Doublet System Pr0.05La0.95Pb3

We measure the temperature dependence of the nonlinear susceptibility χ3, which reflects the fluctuation of quadrupolar moments, in Pr0.05La0.95Pb3 with a Γ3 non-Kramers doublet in the crystal-electric-field ground state to provide evidence of the quadrupolar Kondo effect. Non-Fermi liquid behavior of χ3 with a \(-\ln T\) dependence is detected in the [100] and [110] directions below \(T\approx 2.5\) K, suggesting the screening of quadrupolar moments. In contrast, χ3 in the [111] direction becomes constant below \(T\approx 3\) K. The observed features indicate that a low-lying Γ3 doublet plays a crucial role in the anomalous properties of PrxLa1-xPb3.

Copper(ii) assembling with bis(2-pyridylcarbonyl)amidate and N,N′-2,2-phenylenebis(oxamate)

We herein present the synthesis and X-ray structures of five copper(II) complexes of formulae [Cu(bpca)(CF3SO3)(H2O)]·H2O (1), [Cu(bpca)(Phpr)(H2O)]·3/2H2O (2), {[Cu(bpca)]2[Cu(opba)(H2O)]}·H2O (3), {[Cu(bpca)]2(H2opba)}2·6H2O (4) and [Cu(bpca)(EtH2opba)]n (5), where bpca = bis(2-pyridylcarbonyl)amidate, Phpr = 3-phenylpropionate, CF3SO3(−) = triflate (anion of the trifluoromethanesulphonic acid), H4opba = N,N′-1,2-phenylenebis(oxamic acid), and EtH3opba = monoethyl ester derivative of the H4opba. 1 and 2 are mononuclear copper(II) complexes where the copper atom is five-coordinate in distorted square pyramidal surroundings with a tridentate bpca and a water molecule (1)/carboxylate oxygen (2) building the basal plane and a triflate oxygen (1)/water molecule (2) filling the apical position. 3 is a neutral tricopper(II) complex where the [Cu(opba)(H2O)]2− unit acts as a bis-bidentate ligand toward two peripheral [Cu(bpca)]+ fragments. The three crystallographically independent copper(II) ions in 3 are five-coordinate with two nitrogen and two oxygen atoms (inner copper atom)/three bpca-nitrogen and an oxamate oxygen (outer copper atom) building the basal plane plus a water molecule (inner copper)/an oxamate oxygen (outer copper) in the apical position (inner copper atom) of somewhat distorted square pyramidal surroundings. 4 is a centrosymmetric tetracopper(II) compound where four [Cu(bpca)]+ fragments are assembled by two H2opba2− groups adopting an unusual bidentate/bis-monodentate bridging mode. The two crystallographically independent copper(II) ions in 4 are also five-coordinate having the three bpca-nitrogens in basal positions, the other two sites of the distorted square pyramid being filled by two oxygens of either a bidentate oxamate (at one copper centre) or two bis-monodentate oxamates (at the other copper atom). 5 is a zigzag chain of [Cu(bpca)(H2O)]+ units which are connected through the EtH2opba− ligand adopting a bidentate/monodentate bridging mode across the monodeprotonated oxamate group. Each copper(II) ion in 5 is six-coordinate in an elongated octahedral CuN3O3 chromophore. The magnetic properties of 3–5 were investigated in the temperature range 1.9–300 K. 3 exhibits an intermediate intramolecular antiferromagnetic interaction [J = -65.8(2) cm(-1) with the Hamiltonian H = -J(S(Cu1)·S(Cu2) + S(Cu2)·S(Cu3))] which leads to a low-lying spin doublet at low temperatures. A weak antiferromagnetic coupling between the inner copper(II) ions occurs in 4 [J = -2.36(2) cm(-1), H = -JS1·S2)] and a very small intrachain antiferromagnetic interaction is observed in 5 [J = -0.17(1) cm(-1) with H = -J∑(i)S(i)·S(i+1)]. These values are analyzed by means of simple orbital symmetry considerations and compared with those previously reported for parent systems.

Ab initio study of vibronic transitions between x2π and 12Σ+ electronic states of HCP+ ion

The ground and low-lying excited doublet electronic states of the HCP+ ion were studied by means of multireference configuration interaction method. Vibronic energy levels of the X2? state of ?, ?, ?, and ? symmetry, up to the 2500 cm-1, have been calculated variationally, employing previously developed ab initio methods which take into account vibronic and spin-orbit interactions. Obtained vibronic wave functions were used to estimate transition moments between vibronic energy levels of the X2? and 12?+ electronic states. Results were compared to available experimental and theoretical data.