Large Electron Binding Energies Research Articles

The transport mechanisms at localized states of thin films of GexAsySe1-x-y chalcogenide glasses under off-equilibrium conditions

The resistance of chalcogenide glass GexAsySe1–x–y film is difficult to be observed due to the electrons pinned near the Fermi level, the large electron binding energy, and the large film resistance. Because the resistance is too large, the test method of Hall effect cannot be used to investigate the electrical properties for chalcogenide glass. In this work, the resistance relaxation states of a series of GexAsySe1–x–y films with different components are observed by reducing the resistance under non-equilibrium temperature conditions from 300 to 440 K, and then the local state electron transport mechanism is investigated. It is interesting that the electrical properties parameters show three relaxation states: 1) The conventional trend is that the conductivity decreases with the increase of temperature. 2) One particular trend is that the resistance presents a wavy shape as the temperature increases. 3) The most special trend is that as the temperature is raised during the conductivity measurements, the conductivity increases before decreases after having reach a certain temperature. Computer calculation results show that the Boltzmann fit formula is more suitable than simply Boltzmann formula for GexAsySe1–x–y chalcogenide film in terms of a low-mobility semiconductor with deep Fermi level and hopping conduction. Through calculations, it is found that three relaxation states are decided by the density of the localized states at Fermi level.

Magnesium-Based Clusters as Building Blocks of Electrolytes in Lithium-Ion Batteries.

Superhalogens, owing to their large electron affinity (EA, exceeding those of any halogen atom), play an essential role in physical chemistry as well as new material design. They have applications in hydrogen storage and lithium-ion batteries. Owing to the unique geometries and electronic features of magnesium-based clusters, their potential to form a new class of lithium salts has been investigated here theoretically. The idea is assessed by conducting ab initio computations on Li+ /Mgn F2n+1-2m Om- compounds (n=2, 3; m=0-3) and analyzing their performance as potential Li-ion battery electrolytes. The Mg3 F7- cluster, with large electron binding energy (EA of 7.93 eV), has been proven to serve as a building block for lithium salts. It is shown that, apart from high electronic stability, the new superhalogen-based electrolytes exhibit a set of desirable properties, including a large band gap, high electrolyte stability window, easy mobility of the Li+ , and favorable insensitivity to water.

Microcalorimeters for X-Ray Spectroscopy of Highly Charged Ions at Storage Rings

X-ray spectroscopy of highly charged heavy ions is an important tool for the investigation of many topics in atomic physics. Such highly charged ions, in particular hydrogen-like uranium, are investigated at heavy ion storage rings, where high charge states can be produced in large quantities, stored for long times and cooled to low momentum spread of the ion beam. One prominent example is the determination of the 1s Lamb Shift in hydrogen-like heavy ions, which has been investigated at the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research. Due to the large electron binding energies, the energies of the corresponding photon transitions are located in the X-ray regime. To determine the transition energies with high accuracy, highly resolving X-ray spectrometers are needed. One concept of such spectrometers is the concept of microcalorimeters, which, in contrast to semiconductor detectors, uses the detection of heat rather than charge to detect energy. Such detectors have been developed and successfully applied in experiments at the ESR. For experiments at the Facility for Antiproton and Ion Research (FAIR), the Stored Particles and Atoms Collaboration (SPARC) pursues the development of new microcalorimeter concepts and larger detector arrays. Next to fundamental investigations on quantum electrodynamics such as the 1s Lamb Shift or electron–electron interactions in two- and three-electron systems, X-ray spectroscopy may be extended towards nuclear physics investigations like the determination of nuclear charge radii.

Mg3F7: A superhalogen with potential for new nanomaterials design

AbstractThe stability of the Mg3F7 cluster and its ability to ionize nanoparticles has been investigated theoretically. At the CCSD(T) level of theory, the Mg3F7 cluster has been confirmed to be superhalogen due to its high adiabatic electron affinity (7.9 eV). The corresponding daughter anionic species (Mg3F7−) displays a highly symmetric (C3v) umbrella‐like structure and magic cluster stability. The extra electron of the Mg3F7− anion aggregates on the terminal fluorine ligands with non‐negligible distribution occurring on the bridging F units too. These two properties lower both the kinetic and potential energies of the extra electron respectively and thus lead to large electron binding energy. When interacting with the fullerene nanoparticle (C60), the radical neutral Mg3F7 superhalogen captures an electron and forms stable and strongly bound “binary salts” consisted of Mg3F7− anion and C60•+ radical cation. Thus, Mg3F7 can be used as an effective oxidizing agent to construct new ionized nanomaterials.

Relativistic dynamics of the Compton diffusion on a bound electron

A covariant relativistic formalism for the electron-photon and nuclear dynamics is summarised making more accurate predictions in agreement with experiments for Compton scattering in shells with large electron binding energy. An exact solution for the Dirac equation for an electron in the nuclear Coulomb field is obtained, in order to write the relativistic dynamics for this QED process. This is a preparation for the calculation of the relativistic cross-section for Compton scattering on bound electrons; as a precision test for QED.

Fluoride sample matrices and reaction cells — new capabilities for isotope measurements in accelerator mass spectrometry

Two new techniques, which extend the range of elements that can be analyzed by Accelerator Mass Spectrometry (AMS), and which increase its isobar selection capabilities, have been recently introduced. The first consists of embedding the sample material in a fluoride matrix (e.g. PbF2), which facilitates the production, in the ion source, of fluoride molecular anions that include the isotope of interest. In addition to forming anions with large electron binding energies and thereby increasing the range of analysable elements, in many cases by selection of a molecular form with a particular number of fluorine atoms, some isobar discrimination can be obtained. The second technique, for the significant reduction of atomic isobar interferences, is used following mass selection of the rare isotope. It consists of the deceleration, cooling and reaction of the rare mass beam with a gas, selected so that unwanted isobars are greatly attenuated in comparison with the isotope of interest. Proof of principle measurements for the analysis of 36C1 and 41Ca have provided encouraging results and work is proceeding on the integration of these techniques in a new AMS system planned for installation in late 2012 at the University of Ottawa.

Enormously large (approaching 14 eV!) electron binding energies of [formula omitted] ( n = 1–5, 7, 9, 12) anions

The vertical electron detachment energies (VDE) of a series of [ H n F n + 1 ] - anions (where n = 1–5, 7, 9, 12) were calculated at the outer valence Green function level with the 6-311++G(3df,3pd) basis sets. Enormously large electron binding energies of these anions (in the 6.98–13.87 eV range) were predicted and discussed. The [H 12F 13] − species with the VDE of 13.87 eV was identified as the most strongly bound anion studied and described in the literature thus far.

Investigating the Weak to Evaluate the Strong: An Experimental Determination of the Electron Binding Energy of Carborane Anions and the Gas phase Acidity of Carborane Acids

Five CHB(11)X(6)Y(5)(-) carborane anions from the series X = Br, Cl, I and Y = H, Cl, CH(3) were generated by electrospray ionization, and their reactivity with a series of Brønsted acids and electron transfer reagents were examined in the gas phase. The undecachlorocarborane acid, H(CHB(11)Cl(11)), was found to be far more acidic than the former record holder, (1-C(4)F(9)SO(2))(2)NH (i.e., DeltaH degrees (acid) = 241 +/- 29 vs 291.1 +/- 2.2 kcal mol(-1)) and bridges the gas-phase acidity and basicity scales for the first time. Its conjugate base, CHB(11)Cl(11)(-), was found by photoelectron spectroscopy to have a remarkably large electron binding energy (6.35 +/- 0.02 eV) but the value for the (1-C(4)F(9)SO(2))(2)N(-) anion is even larger (6.5 +/- 0.1 eV). Consequently, it is the weak H-(CHB(11)Cl(11)) BDE (70.0 kcal mol(-1), G3(MP2)) compared to the strong BDE of (1-C(4)F(9)SO(2))(2)N-H (127.4 +/- 3.2 kcal mol(-1)) that accounts for the greater acidity of carborane acids.

Mg2Cl5 - and Mg3Cl7 - Superhalogen Anions

The vertical electron detachment energies of Mg2Cl5– and Mg3Cl7– superhalogen anions were calculated at the outer valence Green function level with 6–311+G(3df) basis sets. These species were found to form rather unusual geometrical structures, each of which corresponds to a stable anionic state exhibiting superhalogen nature. The global minimum structure of Mg2Cl5– was found to possess D3h symmetry, which can be described as a system in which two central magnesium atoms are linked via a symmetrical triangle formed by three chlorine atoms, whereas the lowest-energy structure for Mg3Cl7– was found to have C3v symmetry, which can be viewed as a fragment of chloromagnesite crystal lattice. Extremely large electron binding energies of these anions (exceeding 6.5 eV in all cases) were predicted and discussed.

Is hydrogen capable of playing a central atom role in superhalogen anions?

The vertical electron detachment energies (VDE) of FHF −, ClHCl −, BrHBr −, and H 2 F 3 - anions were calculated at the outer valence Green function level with the aug-cc-pVTZ basis sets. Relatively large electron binding energies of these anions (approaching 8 eV in the case of H 2 F 3 - anion) were predicted and discussed. It was proposed the hydrogen atoms may act as central atoms in these species, analogously to metal atoms in mono- and polynuclear superhalogen anions.

Unusual structures of [formula omitted] superhalogen anion

The vertical electron detachment energies (VDE) of three Mg 2 F 5 - anions were calculated at the outer valence Green function level with the 6-311 + G(3df) basis sets. This species was found to form unusual geometrical structures each of which corresponds to an anionic state exhibiting superhalogen nature. The global minimum structure was described as a system in which two central magnesium atoms are linked via symmetrical triangle formed by three fluorine atoms. Extremely large electron binding energies of these anions (exceeding 8.5 eV in all cases) were predicted and discussed.

Theoretical Search for Anions Possessing Large Electron Binding Energies

AbstractThe vertical electron detachment energies (VDE) of several anions were calculated at the OVGF level with 6‐311++G(d) basis sets. The negatively charged species studied were chosen based on the observation that the largest electron binding energies for such systems are expected to be found for the anions whose neutral parents are polynuclear superhalogens. The largest vertical electron binding energy of 12.63 eV was found for Ta3F16−, and this is the largest excess electron binding energy of a molecular system reported in the literature thus far. Moreover, the VDEs of 12.63 and 12.20 eV calculated for Ta3F16− and As3F16−, respectively, exceed the upper limit for the excess electron binding energy (thought to be 12 eV). Several other anions were also found [at the OVGF/6‐311++G(d) level] to possess very large VDEs (i.e. Al2Br7−: 7.08 eV, Al2Cl7−: 7.75 eV, Al2F7−: 11.16 eV, P2F11−: 10.95 eV, V2F11−: 10.98 eV, As2F11−: 11.43 eV, and Ta2F11−: 11.84 eV). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Dissociative Photodetachment Dynamics of Isomeric Forms of N3O2-

The dissociative photodetachment of N3O2- at 532, 355, and 266 nm has been studied using coincident photoelectron and photofragment translational spectroscopy in a fast-ion beam. The photoelectron spectra confirm previous experimental evidence for a weakly perturbed NO-(N2O) complex and show for the first time a broad continuum at large electron-binding energies. Translational energy release spectra exhibit both low- and high-energy-release channels, indicating that two regions of the NO−N2O neutral potential energy surface with very different intermolecular repulsion are accessed. Photoelectron−photofragment coincidence data confirm that the high translational energy release events are correlated with the continuum in the photoelectron spectrum. These dissociative photodetachment dynamics are consistent with the existence of two isomeric species, an ion−dipole complex with the charge localized on the NO moiety and a molecular anion with an estimated stability of 2.0 ± 0.2 eV relative to NO + N2O + e-.