Composition Of Wave Functions Research Articles

Theoretical Engineering of Singlet Fission Kinetics in Perylene Bisimide Dimer with Chromophore Rotation.

We investigated the potential of chromophore's rotations to tune singlet fission (SF) kinetics in perylene bisimide (PBI) dimers in addition to relative horizontal displacements. The total number of 250 PBI dimers (five displacements along the long and short axis of PBI, respectively, and ten rotation angle changes from parallel to perpendicular alignment) was examined. Ground-state energies showed that dimer formation is favored in all orientations with some differences in interaction strength. Time-dependent density functional theory predicted S1 and T1 excitons' energy, and the thermodynamic feasibility of SF process was judged by the energy difference between a S1 exciton and twice of T1 excitons. In addition, we also estimated the relative rate of multiexciton generation step by the three-state kinetic model with the results of restricted active space employing double spin-flip. Nine promising orientations including two parallel PBI dimers and seven twisted ones were discussed. Wave function composition analysis showed that SF occurs mainly through the superexchange mechanism in various twisted PBI dimers, but the direct two-electron and coherent pathway could be operative at the particular positions. Quantum chemical simulations suggested the rotation as an effective tool to tune SF efficiency in PBI dimers, which is helpful to substantiate more efficient SF material.

Search for the 1/2+ intruder state in P35

The excitation energy of deformed intruder states (specifically the 2p2h bandhead) as a function of proton number $Z$ along $N=20$ is of interest both in terms of better understanding the evolution of nuclear structure between spherical $^{40}$Ca and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At the center of the $N=20$ Island of Inversion, the npnh (where n=2,4,6) neutron excitations across a diminished $N=20$ gap result in deformed and collective ground states, as observed in $^{32}$Mg. In heavier isotones, npnh excitations do not dominate in the ground states, but are present in the relatively low-lying level schemes. With the aim of identifying the expected 2p2h$\otimes\mathrm{s}_{1/2^+}$ state in $^{35}$P, the only $N=20$ isotone for which the neutron 2p2h excitation bandhead has not yet been identified, the $^{36}$S(d,$^3$He)$^{35}$P reaction has been revisited in inverse kinematics with the HELical Orbit Spectrometer (HELIOS) at the Argonne Tandem Linac Accelerator System (ATLAS). While a candidate state has not been located, an upper limit for the transfer reaction cross-section to populate such a configuration within a 2.5 to 3.6\,MeV energy range, provides a stringent constraint on the wavefunction compositions in both $^{36}$S and $^{35}$P.

An Ab Initio Computational Study of Electronic and Structural Factors in the Isomerization of Donor-Acceptor Stenhouse Adducts.

In this work, the photochemically and thermally induced isomerization of multiple donor-acceptor Stenhouse adducts (DASAs) of the first, second, and third generation is studied by means of state-of-the-art ab initio electronic structure methods leading to new insight into multiple facets of the reaction mechanism. Importantly, prior to any studies of the reaction mechanism, a set of test calculations demonstrate the suitability of the applied ADC(2) and CC2 methods in the present context. An important aspect in this regard is the availability of electronic energies and gradients under implicit consideration of solvent effects. On the basis of calculated reaction energies and barriers as well as a thorough analysis of the wave function compositions, interesting features of the reaction mechanism are deduced. For example, the closed form of second- and third-generation DASAs can be significantly stabilized by π - π interactions between the donor and acceptor termini when certain structural requirements are fulfilled. The central point of this work concerns the delicate balance between neutral and zwitterionic resonance structures that governs the relative barrier height for the crucial C2-C3 and C3-C4 bond rotations. Finally, a set of calculations on yet unreported derivatives highlights how this balance and hence the barrier heights can be tuned through variation of the donor-acceptor strength as well as the solvent polarity.

The Low Lying Double-Exciton State of Conjugated Diradicals: Assessment of TDUDFT and Spin-Flip TDDFT Predictions

Conjugated singlet ground state diradicals have received remarkable attention owing to their potential applications in optoelectronic devices. A distinctive character of these systems is the location of the double-exciton state, a low lying excited state dominated by the doubly excited HOMO,HOMOLUMO,LUMO configuration, (where HOMO=highest occupied molecular orbital, LUMO=lowest unoccupied molecular orbital) which may influence optical and other photophysical properties. In this contribution we investigate this specific excited state, for a series of recently synthesized conjugated diradicals, employing time dependent density functional theory (TDDFT) based on the unrestricted parallel spin reference configuration in the spin-flip formulation (SF-TDDFT) and standard TD calculations based on the unrestricted antiparallel spin reference configuration (TDUDFT). The quality of computed results is assessed considering diradical and multiradical descriptors, and the excited state wavefunction composition.

A systematic construction of configuration interaction wavefunctions in the complete CI space.

We introduce a systematic approach to construct configuration interaction (CI) wavefunctions through a variant of the Monte Carlo CI (MCCI) method termed systematic-MCCI. Within this approach, the entire interacting space is systematically considered in batches, with the most important configurations across all batches becoming potential additions to the wavefunction. We compare this method to MCCI and a novel pruned-full configuration interaction (FCI) approach. For the ground state of neon, as described by the cc-pVTZ basis, we observe no apparent difference between systematic-MCCI, pruned-MCCI, and MCCI, with all recovering 99% of the correlation energy and producing a very similar wavefunction composition. We then consider the potential energy surface corresponding to the symmetric double hydrogen dissociation of water within a cc-pVDZ basis. Once again MCCI performs comparably to the systematic approaches. Despite systematic-MCCI having longer run times across the number of processors considered, we do observe very good scalability. We then extend this comparison to the first A1 excited energy of carbon monoxide using the cc-pVDZ basis where the MCCI methods perform similarly, approximating this aforementioned energy to within 0.1 eV despite vast reduction in the wavefunction size. Finally, we consider the chromium dimer with the cc-pVTZ basis and 18 frozen orbitals. Here, we find that the systematic approach avoids being trapped in the same local minimum of configuration space as MCCI, yet MCCI can reach a lower energy by repeating the calculation with more processors.

Microscopic Manifestations of the Wave Nature and the Fifth Fundamental Field

In Quantum Mechanics, one knows that the wave function interpretation is probabilistic. We previously established that any particle scalar field is the cause of its existence. Here, one examined the plane solution regarding a moving particle in vacuum, through the relativistic formalism. It appeared the following. (i) The solution presents four alternatives, like in Dirac unified formalism; when searching stationary solutions of the system vacuum-particle or the system vacuum-antiparticle. (ii) Considering the former, each spinner component shows the interaction of one particle charge with three vacuum fermions of spin-½; each oriented along one space direction. Furthermore, this allows deducting the triple nature of any gauge fermion. (iii) Each solution case is definable with a same wave front width. This determination became possible from the vector companion of that wave function one introduced before. Here, this points out the existence of transverse time. (iv) Both functions let emphasizing the existence of a third fundamental field of long range, which is identifiable to the fundamental spin field. (v) This unites the particle spin and orbital momenta and bears in addition a magnetic-like field, which is yet unknown. (vi) According to the charge, a particle field is observable in wave phenomena, from the manifestations of its gauge fermions or gauge bosons; when ejected from their stationary states by a perturbation… At last, the results highlight the quantum composition of wave functions, the spin-field patency, and the wave nature manifestation from five differentiable fields.

Revealing microscopic origins of shape coexistence in the Ni isotopic chain

In a two–neutron transfer experiment, performed in Bucharest in July 2016 at sub–Coulomb barrier energy,a photon decay hindered – solely – by a nuclear shape change was identified in the 66Ni nucleus. Such a rare process, at spin zero, was clearly observed before only in actinide nuclei in the 1970’s,where fission isomers were found. The experimental findings on 66Ni have been well reproduced by the Monte Carlo Shell Model Calculations of the Tokyo group, which predict a multifaceted scenario of coexistence of spherical, oblate and prolate shapes in neutron–rich Ni isotopes. The results on 66Ni encouraged a comprehensive gamma–spectroscopy investigation of neutron–rich Ni isotopes, in particular 62Ni and 64–Ni, at IFIN–HH (Bucharest), IPN Orsay and ILL (Grenoble), employing different reaction mechanisms to pin down the wave function composition of selected excited states. The aim is to shed light on the microscopic origin of deformation in neutron–rich Ni nuclei, possibly locating other examples of “shape–isomer–like” structures inthis region.

K-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures

Nanostructures based on buried interfaces and heterostructures are at the heart of modern semiconductor electronics as well as future devices utilizing spintronics, multiferroics, topological effects, and other novel operational principles. Knowledge of electronic structure of these systems resolved in electron momentum k delivers unprecedented insights into their physics. Here we explore 2D electron gas formed in GaN/AlGaN high-electron-mobility transistor heterostructures with an ultrathin barrier layer, key elements in current high-frequency and high-power electronics. Its electronic structure is accessed with angle-resolved photoelectron spectroscopy whose probing depth is pushed to a few nanometers using soft-X-ray synchrotron radiation. The experiment yields direct k-space images of the electronic structure fundamentals of this system—the Fermi surface, band dispersions and occupancy, and the Fourier composition of wavefunctions encoded in the k-dependent photoemission intensity. We discover significant planar anisotropy of the electron Fermi surface and effective mass connected with relaxation of the interfacial atomic positions, which translates into nonlinear (high-field) transport properties of the GaN/AlGaN heterostructures as an anisotropy of the saturation drift velocity of the 2D electrons.

Spectroscopic Study of EUV and SXR Transitions of Ba XLVI

An extensive set of energy levels, inverse radiative rates, wave-function composition in LSJ and JJ coupling schemes for the lowest 162 fine structure levels along with transition wavelengths, oscillator strengths, line strengths and transition probabilities for electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2) and magnetic quadrupole (M2) EUV and SXR transitions from the ground state have been presented for Ba XLVI. For these calculations, the fully relativistic Multiconfiguration Dirac-Fock (MCDF) approach is employed. The QED corrections due to vacuum polarization and self-energy effects and Breit correction due to the exchange of virtual photons between two electrons are fully considered. To assess the authenticity and credibility of presented results, analogous calculations have also been performed by using a fully relativistic configuration interaction program (Flexible Atomic Code) based on self-consistent Dirac-Fock-Slater iteration method. Extreme Ultraviolet (EUV) and Soft X-ray (SXR) transitions are also identified. Comparison is also made with the available experimental and theoretical data. These accurate data are expected to be useful in fusion research and astrophysical investigations and applications.

Energy levels and radiative rates for Ne-like ions from Cu to Ga

Energy levels, lifetimes and wave function compositions are computed for 127 fine structural levels in Ne-like ions ( $$Z=29{-}31$$ ). Configuration interaction has been included among 51 configurations (generating 1016 levels) and multiconfigurational Dirac–Fock method is used to generate the wave functions. Similar calculations have also been performed using the fully relativistic flexible atomic code (FAC). Transition wavelength, oscillator strength, transition probabilities and line strength are reported for electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) transitions from the ground level. We compared our calculated results with the available data in the literature. The calculated results are found to be in close agreement with the previous results. Further, we predict some new atomic data which may be important for plasma diagnostics.

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study.

Inelastic neutron scattering (INS) has been used to investigate the crystal field (CF) magnetic excitations of the analogs of the most representative lanthanoid-polyoxometalate single-molecule magnet family: Na9[Ln(W5O18)2] (Ln = Nd, Tb, Ho, Er). Ab initio complete active space self-consistent field/restricted active space state interaction calculations, extended also to the Dy analog, show good agreement with the experimentally determined low-lying CF levels, with accuracy better in most cases than that reported for approaches based only on simultaneous fitting to CF models of magnetic or spectroscopic data for isostructural Ln families. In this work we demonstrate the power of a combined spectroscopic and computational approach. Inelastic neutron scattering has provided direct access to CF levels, which together with the magnetometry data, were employed to benchmark the ab initio results. The ab initio determined wave functions corresponding to the CF levels were in turn employed to assign the INS transitions allowed by selection rules and interpret the observed relative intensities of the INS peaks. Ultimately, we have been able to establish the relationship between the wave function composition of the CF split LnIII ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na9[Ln(W5O18)2] family.

Atomic structure calculations and study of line intensity ratio for Kr XXIV

In this work, we provide a detailed and elaborate theoretical study of atomic data along with plasma parameters for Kr XXIV. We have computed energy levels, lifetimes, and wave-function compositions for the lowest 148 fine-structure levels by implementing the multi-configuration Dirac–Fock method with the addition of quantum electrodynamics as well as Breit corrections. We have also given the radiative data among 148 levels for electric dipole (E1) transition, which lie in the extreme ultraviolet range. We have compared our calculated results with NIST and other theoretical results available in the literature and attain a good agreement. Because of the unavailability of sufficient and complete data for higher excited levels for Kr XXIV in the literature, a similar calculation has also been compiled using fully relativistic flexible atomic code (FAC) to access the credibility and integrity of our results. On the other hand, we have also presented the line intensity ratio and plasma parameters for optically thin plasma, which are not published anywhere in the literature, and we believe that our presented results may be advantageous in plasma modeling and astrophysical and fusion plasma research applications.

On the performance of DFT/MRCI-R and MR-MP2 in spin–orbit coupling calculations on diatomics and polyatomic organic molecules

ABSTRACTWe have investigated the performance of different multi-reference quantum chemical methods with regard to electronic excitation energies and spin–orbit matrix elements (SOMES). Among these methods are two variants of the combined density functional theory and multi-reference configuration interaction method (DFT/MRCI and DFT/MRCI-R) and a multi-reference second-order Møller–Plesset perturbation theory (MR-MP2) approach. Two variants of MR-MP2 have been tested based on either Hartree–Fock orbitals or Kohn–Sham orbitals of the BH-LYP density functional. In connection with the MR-MP2 approaches, the first-order perturbed wave functions have been employed in the evaluation of spin–orbit coupling. To validate our results, we assembled experimental excitation energies and SOMES of eight diatomic and fifteen polyatomic molecules. For some of the smaller molecules, we carried out calculations at the complete active space self-consistent field (CASSCF) level to obtain SOMEs to compare with. Excitation energies of the experimentally unknown states were assessed with respect to second-order perturbation theory corrected (CASPT2) values where available. Overall, we find a very satisfactory agreement between the excitation energies and the SOMEs obtained with the four approaches. For a few states, outliers with regard to the excitation energies and/or SOMEs are observed. These outliers are carefully analysed and traced back to the wave function composition.

Atomic structure calculations for Br-like ions

Energy levels, wavefunction compositions, and lifetimes are computed for all levels of 4s24p5, 4s24p44d, and 4s4p6 configurations in Br-like ions (Z = 47–50). We use the multiconfigurational Dirac–Fock method to generate the wavefunctions. We also present the transition wavelengths, oscillator strengths, transition probabilities, and line strengths for the electric dipole (E1) transition from the ground state configuration. We compare our calculated results with the available data in the literature and good agreement is obtained, which confirms the quality of our results. Moreover, we predict some new atomic data that have not been available so far and may be important for plasma diagnostic analysis in fusion plasma.

Lifetimes of4p54dlevels in highly ionized atoms

Energy levels, lifetimes, and wave function compositions have been computed for all atomic states of the $4{p}^{6}$ and $4{p}^{5}4d$ configurations using the multiconfiguration Dirac-Hartree-Fock method. Calculations were done by parity and the configuration state function expansions were obtained by allowing single and double substitutions from the the $4{p}^{6}$ and $4{p}^{5}4d$ single references with orbitals in an orbital set that was extended to $n=7$ and all possible angular symmetries. Lifetimes are computed from $E1$, $E2$, and $M1$ transitions between these levels. Energy levels and transition energies (or wavelengths) are compared with other theory and experiment, when available. Transition data for the $4{p}^{6}{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ -- $4{p}^{5}\phantom{\rule{0.16em}{0ex}}4d\phantom{\rule{0.16em}{0ex}}J=1$ transitions are investigated in detail with respect to convergence of transition energies and the length and velocity forms of the line strengths. By classifying the upper states by $J$, parity $(\ensuremath{\pi})$, and position, the compositions of the states with the same three quantum number change smoothly as a function of the nuclear charge $Z$ and transition energies and transition matrix elements can be approximated by polynomial expressions in $Z.$ A zero in the transition matrix element for the ${}^{1}{S}_{0}\phantom{\rule{4.pt}{0ex}}\text{\ensuremath{-}}{\phantom{\rule{4.pt}{0ex}}}^{3}{P}_{1}^{o}$ transition leads to a long lifetime at $Z\ensuremath{\approx}58$.

What we can learn from the norms of one-particle density matrices, and what we can't: some results for interstate properties in model singlet fission systems.

The utility of the norms of one-particle density matrices, ∥γ∥, for understanding the trends in electronic properties is discussed. Using several model systems that are relevant in the context of singlet fission (butadiene, octatetraene, and ethylene dimer), the dependence of interstate properties (such as transition dipole moments and nonadiabatic couplings, NACs) on molecular geometries is investigated. ∥γ∥ contains the principal information about the changes in electronic states involved, such as varying degree of one-electron character of the transition; thus, it captures leading trends in one-electron interstate properties (i.e., when ∥γ∥ is small, the respective interstate matrix elements are also small). However, finer variations in properties that arise due to the dependence of the matrix elements of the respective operators may not be reproduced. Analysis of NACs in ethylene dimer reveals that intermolecular components of NACs follow the trends in ∥γ∥ well, as they are determined primarily by the characters of the two wave functions; however, intramolecular components depend on the relative orientation of the two moieties via the dependence in the derivative of the electron-nuclear Coulomb operator. Therefore, intramolecular NACs may exhibit large variations even when the changes in ∥γ∥ are small. We observe large NACs at perfectly stacked geometry; however, larger values (by a factor of 1.6) are observed at slip-stacked (along the long axis) geometries. Larger values of NACs at slip-stacked configurations are due to the breaking of symmetry of the local environment of the heavy atoms and not due to the wave function composition. We found that the variations in ∥γ∥ for ethylene dimer are due to a varying admixture of the charge-resonance configurations in the S1 state, whereas the (1)ME state retains its pure multiexciton character.

Atomic structure calculations for F-like tungsten

Energy levels, wavefunction compositions and lifetimes have been computed for all levels of 1s22s22p5, 1s22s2p6, 1s22s22p43s, 1s22s22p43p, and 1s22s22p43d configurations in highly charged F-like tungsten ion. The multiconfigurational Dirac—Fock method (MCDF) is adopted to generate the wavefunctions. We have also presented the transition wavelengths, oscillator strengths, transition probabilities, and line strengths for the electric dipole (E1) and magnetic quadrupole (M2) transition from the 1s22s22p5 ground configuration. We have performed parallel calculations with the flexible atomic code (FAC) for comparing the atomic data. The reliability of present data is assessed by comparison with other theoretical and experimental data available in the literature. Good agreement is found between our results and those obtained using different approaches confirm the quality of our results. Additionally, we have predicted some new atomic data for F-like W that were not available so far and may be important for plasma diagnostic analysis in fusion plasma.

Atomic Data for He-like Tungsten

Atomic data on high-Z materials are important for impurity diagnostics due to its possible use in the next generation fusion devices including astrophysics. For this purpose, in the present paper, energies, lifetimes and wave-function compositions have been computed for all level of 1s$^2$, 1s2l,1s3l, 1s4l, 1s5l and 1s6l in highly charged He-like tungsten ion (W LXXIII). Also, we have presented the transition wavelengths, oscillator strengths, transition probabilities and line strengths for the electric dipole (E1) transitions from the levels 1s$^2$, 1s2s and 1s2p. Our reported results have been obtained using the fully relativistic GRASP code including the correlations within the $n = 6$ complex. The validity of the method is assessed through the comparison with the other results previously published. The excellent agreement observed between our new GRASP results and those obtained using different approaches confirm the accuracy of our results.

Multiconfigurational Dirac–Fock atomic structure calculations for Cl-like tungsten

Energy levels, lifetimes, and wavefunction compositions have been calculated for all levels of odd parity 3s23p5 ground configuration as well as 3s3p6 and 3s23p43d even parity excited configurations in highly charged Cl-like tungsten ion. Transition probabilities, oscillator strengths, and line strengths for E1, E2, M1, and M2 transitions have been obtained using the fully relativistic multiconfiguration Dirac–Fock (MCDF) approach including the correlations within the n = 3 complex, some n = 3 → n = 4 single and double excitations and Breit and quantum electrodynamics effects. For comparison from our calculated energy levels, we have also calculated the energy levels by using the fully relativistic flexible atomic code (FAC). The validity of the method is assessed by comparison with previously published experimental and theoretical data. The excellent agreement observed between our calculated results and those obtained using different approaches confirm the accuracy of our results. Additionally, we have predicted some new atomic data for W57+ that are not available so far and may be important for plasma diagnostic analysis in fusion plasma.

A new spin-oriented nuclei facility: POLAREX

Using the On-Line Nuclear Orientation method, POLAREX (POLARization of EXotic nuclei) is a new facility allowing to study the anisotropic decay of spin-oriented nuclei. Based on the combination of on-line implantation of radioactive nuclei with Low Temperature Nuclear Orientation technique and Nuclear Magnetic Resonance, POLAREX allows to measure nuclear electromagnetic moments and ground-state spins, in the aim to get information about the wave function composition of the nuclear state. Polarized nuclei can also be used to study fundamental interactions involving nuclear -decay asymmetries. The POLAREX infrastructure will be installed at Accelerateur Lineaire aupres du Tandem d’Orsay in order to study neutron-rich nuclei, some of which have not been studied yet. Will be presented here, all the possibilities of this new facility and a non exhaustive scientific program.