Determined Energy Levels Research Articles

Interaction of zero energy levels with crystal defects in graphene. A network theory study

Applying network theory, we present relations concerning the degeneracy and localization of the zero energy modes in graphene. We demonstrate that in most of cases network properties of the lattice are responsible for existence and nonexistence of these topological determined energy levels.

Update of Atomic Data for the First Three Spectra of Actinium.

The present article describes a complete reanalysis of all published data on observed spectral lines and energy levels of the first three spectra of actinium (Ac I-III). In Ac I, three previously determined energy levels have been rejected, 12 new energy levels have been found; for six previously known levels, either the J values or the energies have been revised, and the ionization energy has been redetermined with an improved accuracy. In the line list of Ac I, three previous classifications have been discarded, 16 new ones have been found, and three have been revised. In Ac II, 16 new energy levels have been established, and 36 new identifications have been found for previously observed but unclassified lines. In both Ac I and Ac II, new sets of transition probabilities have been calculated. For all three spectra, complete datasets of critically evaluated energy levels, observed lines, and transition probabilities have been constructed to serve as recommended data on these spectra.

Employing Some of Nuclear Models to Study the Energy Levels of Odd Atomic Mass Nuclei

The energy levels and their Gamma Transitions for the nuclei are important characteristics for identify its properties, and the moment of inertia is one of the important parameters in determining energy levels. accordingly many nuclear models have been developed in successive periods of time for this study, according to the movement of the nuclei. The energy levels were calculated for all values of the total nuclear momentum and parity by applying the nuclear shell model and the Generalized Variable Moment of Inertia with the addition of some limits in order to obtain accurate and inclusive results for all Nuclei. In This paper we have include nuclie whom their energy levels have not previously been studied theoretically and for which only experimental data are available and these Nuclei are: (11Na27, 26Fe59, 35Br79, 40Zr81, 39Y91, 38Sr97, 49In107 48Cd121, 77Ir191, 89Ac221) and this model was designed with a developed program (Matlab-2020) and the results were compared with the practical data and they were in good agreement.

The Relation Between Photoconductivity Threshold and Open-Circuit Voltage in Organic Solar Cells

Abstract Most of the solar cell parameters (short-circuit current, fill factor, power conversion efficiency) can only be determined by creating and measuring the solar cell. However, there is an empirical relation that links energy level values of the materials in the active layer to an open-circuit voltage (Uoc) of the solar cell. Due to a variety of possible methods used to determine energy level values and the dispersion of obtained results, this estimate is not always correct. Even if correct energy level values are obtained for separate materials, energy level shift takes place at the interfaces when two materials are mixed. That is why a simple and reliable experimental method for Uoc estimation is required. Usually, photoconductivity is used to obtain the energy gap between molecule ionization energy and electron affinity of a single material. When two materials are mixed, direct charge transfer from donor to acceptor molecule can be observed. The threshold energy (ECT) shows the real difference between donor molecule ionization energy and acceptor molecule electron affinity. This difference should correspond to the Uoc. The present study makes the comparison between the open-circuit voltage estimated from material energy level values, the obtained ECT values for various donor:acceptor systems, and the real Uoc obtained from solar cell measurements. Strong correlation between ECT and Uoc is obtained and the photoconductivity measurements can be used in the estimation of Uoc.

Spectroelectrochemically determined energy levels of PM6:Y6 blends and their relevance to solar cell performance

A systematic spectroelectrochemical approach is presented to precisely determine frontier orbital energies of PM6:Y6 blends in device-relevant films and results are discussed regarding their impact on solar cell performance.

Pure rotational spectrum and structural determination of 1,1-difluoro-1-silacyclopentane

The ground state, pure rotational spectrum of 1,1-difluoro-1-silacyclopentane has been studied using chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy and observed in the 6-20.3 GHz region of the electromagnetic spectrum. This spectrum was acquired leveraging the deep averaging capability of the technique. The parent species, 13C, 29Si, and 30Si singly substituted isotopologues were observed in natural abundance and are reported. Only one conformer, the C2 conformer (half-chair), was observed. This is confirmed with a determined CCCC dihedral angle of -48.1(11)°. The spectrum is comprised of entirely a-type transitions in accordance with quantum chemical calculations. Multiple split transitions are present in the spectrum which have been attributed to a ring-twisting of the carbon atoms attached to the silicon atom in the ring. This motion has the carbons crossing the a-axis in the bc-plane leading to an inversion potential. Potential energy surfaces for the ring-twisting motion were undertaken and the experimentally determined energy level difference observed in comparison to these surfaces is reasonable. A Kraitchman analysis of the experimentally determined, singly substituted isotopologues is in agreement with the optimized, twisted (nonplanar) equilibrium structure. This structure has been compared to other similar silicon-containing ring molecules using second moment arguments and these comparisons are discussed.

Odd-parity autoionizing levels of uranium observed by two-color two-step photoionization optogalvanic spectroscopy

Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels with the first-step laser and by scanning the second-step laser wavelengths. By blocking the first-step laser, single-color, two-photon ionization transitions were also identified. From these results, we have found more than 50 odd-parity autoionizing levels of uranium in the energy, ranging from the ionization potential (49958.4 cm−1) to 51 150 cm−1. The determined energy levels are within ∼±1 cm−1 of previously reported values.

Mono- and Di-Pyrene [60]Fullerene and [70]Fullerene Derivatives as Potential Components for Photovoltaic Devices

In the present work, we report the successful synthesis and characterization of six (two new) fullerene mono- and di-pyrene derivatives based on C60 and C70 fullerenes. The synthesized compounds were characterized by spectral methods (ESI-MS, 1H-NMR, 13C-NMR, UV-Vis, FT-IR, photoluminescence and photocurrent spectroscopy). The energy of HOMO and LUMO levels and the band gaps were determined from cyclic voltammetry and compared with the theoretical values calculated according to the DFT/B3LYP/6-31G(d) and DFT/PBE/6-311G(d,p) approach for fully optimized molecular structures at the DFT/B3LYP/6-31G(d) level. Efficiency of solar cells made of PTB7: C60 and C70 fullerene pyrene derivatives were analyzed based on the determined energy levels of the HOMO and LUMO orbitals of the derivatives as well as the extensive spectral results of fullerene derivatives and their mixtures with PTB7. As a result, we found that the electronic and spectral properties, on which the efficiency of a photovoltaic cell is believed to depend, slightly changes with the number and type of pyrene substituents on the fullerene core. The efficiency of constructed solar cells largely depends on the homogeneity of the photovoltaic layer, which, in turn, is a derivative of the solubility of fullerene derivatives in the solvent used to apply these layers by spincoating.

A simplified method of calculating electronic energy level populations in nonequilibrium plasmas

<sec> In order to investigate the radiative properties of plasma in non local thermodynamic equilibrium (NLTE), it is of great importance to determine energy level populations, which are often obtained by the so-called collisional-radiative (CR) model. As is well known, the CR model is accurate but computationally costly, and thus it is difficult to be applied to engineering calculations for such as complex three-dimensional plasmas.</sec> <sec> In this work, a bound-state characteristic temperature (BCT) method is proposed, which can be used to calculate quickly the energy level populations in non-equilibrium plasmas. In this method, we assume that for each kind of ionization stage, the bound-state population is Boltzmannian at a certain characteristic temperature. The assumed characteristic temperature is related to the degree of none-equilibrium and may be different from the electronic temperature of the plasma. Based on a modified Saha equation, the assumed characteristic temperature can be calculated easily, and then the energy level populations are obtained conveniently. Five cases of non-equilibrium neon plasma at variable electronic temperatures and densities are investigated and compared with the results from a CR model. Good agreement is found between them if the degree of non-equilibrium is not very large. It shows that the present method is effective and at least 3000 times faster in computation time than the CR model. The method is very useful in engineering applications.</sec>

A semi-empirical potential energy surface and line list for H<sub>2</sub><sup>16</sup>O extending into the near-ultraviolet

Abstract. Accurate reference spectroscopic information for the water molecule from the microwave to the near-ultraviolet is of paramount importance in atmospheric research. A semi-empirical potential energy surface for the ground electronic state of H216O has been created by refining almost 4000 experimentally determined energy levels. These states extend into regions with large values of rotational and vibrational excitation. For all states considered in our refinement procedure, which extend to 37 000 cm−1 and J=20 (total angular momentum), the average root-mean-square deviation is approximately 0.05 cm−1. This potential energy surface offers significant improvements when compared to recent models by accurately predicting states possessing high values of J. This feature will offer significant improvements in calculated line positions for high-temperature spectra where transitions between high J states become more prominent. Combining this potential with the latest dipole moment surface for water vapour, a line list has been calculated which extends reliably to 37 000 cm−1. Obtaining reliable results in the ultraviolet is of special importance as it is a challenging spectral region for the water molecule both experimentally and theoretically. Comparisons are made against several experimental sources of cross sections in the near-ultraviolet and discrepancies are observed. In the near-ultraviolet our calculations are in agreement with recent atmospheric retrievals and the upper limit obtained using broadband spectroscopy by Wilson et al. (2016, p. 194), but they do not support recent suggestions of very strong absorption in this region.

On the generalised eigenvalue method and its relation to Prony and generalised pencil of function methods

We discuss the relation of a variety of different methods to determine energy levels in lattice QCD simulations: the generalised eigenvalue, the Prony, the generalised pencil of function and the Gardner methods. All three former methods can be understood as special cases of a generalised eigenvalue problem. We show analytically that the leading corrections to an energy E_l in all three methods due to unresolved states decay asymptotically exponentially like exp (-(E_{n}-E_l)t). Using synthetic data we show that these corrections behave as expected also in practice. We propose a novel combination of the generalised eigenvalue and the Prony method, denoted as GEVM/PGEVM, which helps to increase the energy gap E_{n}-E_l. We illustrate its usage and performance using lattice QCD examples. The Gardner method on the other hand is found less applicable to realistic noisy data.

Calculate Energy Levels, Energy Ratios and Electric Quadrupole Transition Probability B(E2), of the Even-Even Yb-164 Isotopes Using IBM-1

The nuclear structure for even-even nuclei estimated by using interacting boson model (IBM-1). Also this program was used to determine energy levels of g- state, energy ratios and electric quadrupole transitions probability B(E2) which have been calculated. Depending on the follow up of energy ground bands (g, β, and γ) . The dynamical symmetry and energy spectrum of selected isotope are determined by B(E2). The electric quadrupole transition probability of the (2ᶢ+-0ᶢ+) transitions for Yb (A=164) isotopes with the dynamical symmetry SU(3)- SU(5) from rotational SU(3) to vibrational SU(5). All obtained results of the study were compared with experimental facts and acceptable agreement obtained.

4D-Structural Dynamics of the Transition State: Free Molecules, Clusters and Nanocrystals

Study of the structural dynamics of matter by methods with high spatially-temporal resolution represents new direction in modern science and provides the understanding of relationship inside the "structure – dynamics – property" triad in the field of physics, chemistry, biology and materials science. Application of femto and attosecond laser pulses for excitation and formation of synchronized ultrashort photoelectron bunches for probing makes it possible to observe coherent dynamics of nuclei and electrons in samples on necessary space-time scales. Using laser spectroscopy one can determine energy levels of the sample and trace their evolution over time. However, the extraction of the structural dynamics of matter from this information is achieved by indirect methods. In the paper authors demonstrate the direct approaches to the study of the coherent dynamics of the nuclei of laser-excited matter in the space-time continuum (4D), based on probing the object with ultra-short electron or X-ray pulses, and describe their experiments, which were carried out using ultrafast electron diffractometer and transmission electron microscope at the Institute of Spectroscopy RAS.

Highly accurate experimentally determined energy levels of H3.

A sub-Doppler rovibrational spectroscopic survey of H3 + has been conducted which included 36 transitions in the ν2 ← 0 fundamental band, 15 transitions in the 2ν2 2←ν2 hot band, and 7 transitions in the 2ν2 2←0 overtone band, improving the uncertainties of most transitions by more than an order of magnitude to ∼4 MHz. Combination differences were used to determine relative energy levels and forbidden rotational transitions up to J = 6. A fit of the ground state to an effective Hamiltonian was used to connect ortho and para states, and to determine the absolute energy levels relative to the forbidden (0, 0) state. Ultimately, 62 rovibrational energy levels in the ground, ν2, and 2ν2 2 states were determined with ∼10 MHz uncertainty. Comparing the experimentally determined energy levels with ab initio calculations revealed an unexpected dependence of the residuals on the quantum number G.

Efficient Polymeric Donor for Both Visible and Near-Infrared-Absorbing Organic Solar Cells

A new ternary polymer, TP, incorporating 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTT), 5-octyl-2-(2-octyldodecyl)-4,6-di(thieno[3,2-b]thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (PPD), and 2-ethylhexyl 3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT) units at a 2:1:1 ratio, was prepared to develop a potential candidate for visible and near-infrared (NIR)-absorbing organic solar cells (OSCs). TP displayed an optical bandgap (Eg) of 1.65 eV with a maximum absorption peak at 558 nm. TP indicates good complementary absorption with visible light, absorbing most typically used fullerene-based acceptors (PC70BM, intense absorption range: 300–450 nm with Eg of 1.80 eV) and nonfullerene acceptors (NFAs), namely, ITIC (intense absorption range: 500–800 nm with Eg of 1.59 eV). In addition, TP exhibits good complementary absorption with NIR-absorbing NFAs, namely, IEICO-4F (intense absorption range: 600–1000 nm with Eg of 1.24 eV). The determined energy levels (−5.31 eV and −3...

Optical properties and electronic structures of Cu2SnS3, Cu2GeS3, and their solid solution Cu2(Ge,Sn)S3

Cu2(GexSn1−x)S3 (CGTS) (0 ≤ x ≤ 1.0) powders were synthesized by mixing elemental powders and sequential heating in 5% H2S gas atmosphere. The crystal structures of CGTS solid solution samples were refined by Rietveld refinement of the powder X-ray diffraction data. CGTS has a monoclinic crystal structure with a space group of Cc (No. 9), and the refined lattice parameters decreased linearly from a = 6.653(7) Å, b = 11.532(5) Å, and c = 6.656(2) Å of Cu2SnS3 (x = 0.0) to a = 6.416(3) Å, b = 11.303(2) Å, and c = 6.434(9) Å of Cu2GeS3 (x = 1.0) with increasing Ge, x. The band-gap energy (Eg) of the Cu2(GexSn1−x)S3 solid solution monotonically increased from 0.87 eV for Cu2SnS3 (x = 0.0) to 1.53 eV for Cu2GeS3 (x = 1.0) with increasing Ge, x. The energy level of the valence band maximum (VBM) from the vacuum level was determined from the ionization energy measured by photoelectron yield spectroscopy (PYS). The determined energy levels of VBM of Cu2SnS3 and Cu2GeS3, and their solid solution samples were shallower than those of Cu2ZnSnS4 and Cu2ZnGeS4, and their solid solution. The energy level of conduction band minimum (CBM) was calculated by adding Eg to VBM level. The energy levels of CBM of Cu2SnS3 and Cu2GeS3, and their solid solution samples were deeper than those of Cu2ZnSnS4 and Cu2ZnGeS4, and their solid solution. Even when the Ge content in Cu2(GexSn1−x)S3 solid solution samples increased, the VBM level did not change significantly but the CBM level increased markedly. We also determined the VBM levels of Cu2SnSe3, Cu2GeSe3, and Cu2(Ge,Sn)Se3 solid solution samples. The energy levels of the VBM of Cu2SnSe3 and Cu2GeSe3, and their solid solution samples were also shallower than those of Cu2ZnSnSe4 and Cu2ZnGeSe4, and their solid solution. On the basis of these results, we discuss the band diagrams of Cu2(Ge,Sn)S3 and Cu2GeSe3 solar cells with the following device structure: absorber layer/CdS buffer layer/ZnO layer.

Quantitative analysis of titanium concentration using calibration-free laser-induced breakdown spectroscopy (LIBS)

Laser-induced breakdown spectroscopy (LIBS) can be used for quantitative and qualitative analysis. Calibration-free LIBS (CF-LIBS) is a method to quantitatively analyze concentration of elements in a sample in local thermodynamic equilibrium conditions without using available matrix-matched calibration. In this study, we apply CF-LIBS for quantitative analysis of Ti in TiO2 sample. TiO2 powder sample was mixed with polyvinyl alcohol and formed into pellets. An Nd:YAG pulsed laser at a wavelength of 1064 nm was focused onto the sample to generate plasma. The spectrum of plasma was recorded using spectrophotometer then compared to NIST spectral line to determine energy levels and other parameters. The value of plasma temperature obtained using Boltzmann plot is 8127.29 K and electron density from calculation is 2.49×1016 cm-3. Finally, the concentration of Ti in TiO2 sample from this study is 97% that is in proximity with the sample certificate.

Removal of accidental degeneracy in semiconductor quantum dots

We present a quantitative analysis of the energy levels and wave functions of carriers in a cubic quantum dot of GaAs embedded in ${\mathrm{Ga}}_{(1\ensuremath{-}x)}{\mathrm{Al}}_{x}\mathrm{As}$ with finite confining potential barriers at their interfaces. The energy spectrum has substantially reduced degeneracies compared to the analytically determined energy levels of the infinite-barrier quantum box of the same dimensions. The level degeneracy of states has been explained by group representations of the point group ${O}_{h}$. Projection operators for the irreducible representations provide a way to obtain the linear combinations of the degenerate wave functions which form a basis set for the representations. Energy-level splittings in the presence of externally applied electric and magnetic fields are also studied.

Electrical properties of zinc oxide – Tetracene heterostructures with different n-type ZnO films

Electrical properties of organic-inorganic p–n heterojunction structures with tetracene (Tc) and zinc oxide (ZnO) films were investigated. The ZnO films had different n-type carrier concentrations that varied from ∼1015 cm−3 to 1019 cm−3. Lower n-type ZnO layers resulted in decreased reverse currents in the ZnO:Al/ZnO/Tc/Au structures and in an improvement of their asymmetric properties. Experimentally determined energy level alignments at the ZnO/Tc interfaces were related to the electrical behavior of the structures. An improved rectification was associated with decreased generation-recombination currents at the ZnO/Tc interface due to an increased organic-inorganic interface energy gap. Current-voltage characteristics were analyzed by a differential approach. Electrical conduction mechanisms including bimolecular recombination as well as trap-filled limited conduction were identified in the investigated structures.

Atomic structure calculations and study of EUV and SXR spectral lines in Cu-like ions

In the present work, we provide a most extensive and detailed study of highly ionized Cu-like ions and diagnose extreme ultraviolet (EUV) and soft X-ray (SXR) transitions with N-shell electron excitation to M-shell and higher shells. We have determined energy levels and lifetimes for lowest 27 fine-structure levels by adopting multiconfiguration Dirac–Fock (MCDF) with the inclusion of quantum electrodynamics (QED) as well as Breit corrections as a first-order perturbation theory. We have also reported complete radiative data for strong electric dipole transitions within lowest 27 levels. We have compared our calculated results with theoretically calculated and experimentally measured results available in the literature, to measure the credibility and genuineness of our results, and achieve good agreement. Further, because of insufficiency of adequate and complete atomic data for higher levels of highly ionized Cu-like ions in the literature, we have performed other equivalent parallel calculations by implementing fully relativistic distorted wave flexible atomic code (FAC) to ensure the accuracy of our results. Additionally, we have also presented transition wavelengths of Nα transitions of high-Z Cu-like ions by using Moseley’s law. We believe that the large amount of atomic data presented in this paper may be useful in fusion and astrophysical plasma and in several applications, especially in lithography and cell biology.