Energy Doublet Research Articles

Interacting Dark Energy in the Dark SU(2) R Model

We explore the cosmological implications of the interactions among the dark particles in the dark $SU(2)_R$ model. It turns out that the relevant interaction is between dark energy and dark matter, through a decay process. With respect to the standard $\Lambda$CDM model, it changes only the background equations. We note that the observational aspects of the model are dominated by degeneracies between the parameters that describe the process. Thus, only the usual $\Lambda$CDM parameters, such as the Hubble expansion rate and the dark energy density parameter (interpreted as the combination of the densities of the dark energy doublet) could be constrained by observations at this moment.

Comparison of structure, morphology, and leach characteristics of multi-phase ceramics produced via melt processing and hot isostatic pressing

Melt processing of multi-phase ceramic waste forms offers potential advantages over traditional solid-state synthesis methods given both the prevalence of melters currently in use and the ability to reduce the possibility of airborne radionuclide contamination. In this work, multi-phase ceramics with a targeted hollandite composition of Ba1.0Cs0.3Cr1.0Al0.3Fe1.0Ti5.7O16 were fabricated by melt processing at 1675 °C and hot isostatic pressing (HIP) at 1250 and 1300 °C. X-ray diffraction analysis (XRD) confirmed hollandite as the major phase in all specimens. Zirconolite/pyrochlore peaks and weaker perovskite reflections were observed after melt processing, while HIP samples displayed prominent perovskite peaks and low-intensity zirconolite reflections. Melt processing produced specimens with large (>50 μm) well-defined hollandite grains, while HIP yielded samples with a more fine-grained morphology. Elemental analysis showed “islands” rich in Cs and Ti across the surface of the 1300 °C HIP sample, suggesting partial melting and partitioning of Cs into multiple phases. Photoemission data revealed multiple Cs 3d spin-orbit pairs for the HIP samples, with the lower binding energy doublets likely corresponding to Cs located in more leachable phases. Among all specimens examined, the melt-processed sample exhibited the lowest fractional release rates for Rb and Cs. However, the retention of Sr and Mo was greater in the HIP specimens.

Metastable dark energy

We build a model of metastable dark energy, in which the observed vacuum energy is the value of the scalar potential at the false vacuum. The scalar potential is given by a sum of even self-interactions up to order six. The deviation from the Minkowski vacuum is due to a term suppressed by the Planck scale. The decay time of the metastable vacuum can easily accommodate a mean life time compatible with the age of the universe. The metastable dark energy is also embedded into a model with $SU(2)_R$ symmetry. The dark energy doublet and the dark matter doublet naturally interact with each other. A three-body decay of the dark energy particle into (cold and warm) dark matter can be as long as large fraction of the age of the universe, if the mediator is massive enough, the lower bound being at intermediate energy level some orders below the grand unification scale. Such a decay shows a different form of interaction between dark matter and dark energy, and the model opens a new window to investigate the dark sector from the point-of-view of particle physics.

Unpaired Majorana Modes in Josephson-Junction Arrays with Gapless Bulk Excitations.

The search for Majorana bound states in solid-state physics has been limited to materials that display a gap in their bulk spectrum. We show that such unpaired states appear in certain quasi-one-dimensional Josephson-junction arrays with gapless bulk excitations. The bulk modes mediate a coupling between Majorana bound states via the Ruderman-Kittel-Yosida-Kasuya mechanism. As a consequence, the lowest energy doublet acquires a finite energy difference. For a realistic set of parameters this energy splitting remains much smaller than the energy of the bulk eigenstates even for short chains of length L∼10.

Spectroscopic studies and density functional theory investigations of a cobalt phthalocyanine derivative

Colloidal solutions at room temperature were used to obtain various polymorphic forms of a [PcCoCN]n and double potassium salt from 1,8 dihydroxyanthraquinone derivative. Nanocrystals in the form α and β were characterized using IR and UV–Vis spectroscopy techniques. Likewise in this context, an energy doublet in the absorption spectra of the monoclinic form at 1.8 and 2eV was observed. The complex structure inherent to the spectra of the CoPc derivative is attributed to the simultaneous presence of both crystalline and molecular phases in the samples. The optical absorption of the compound was also investigated in order to evaluate changes in the electronic structure of these metal organic nanostructures. The absorption spectra of the CoPc derivative recorded in the UV–Vis region manifested two absorption bands, namely the Q- and B- bands. DFT calculations of this structure help to establish the source of the spectroscopic behavior and also lead to a particular phenomenon not known previously in this kind of complex, because the optimized structure of the cobalt complex manifests a very strange deformation of the bond between the anthraquinone derivative and the cobalt atom; the origin of this deformation is also discussed.

Distinguishing spin-orbit coupling and nematic order in the electronic spectrum of iron-based superconductors

The low-energy electronic states of the iron-based superconductors are strongly affected by both spin-orbit coupling and, when present, by the nematic order. These two effects have different physical origins, yet they can lead to similar gap features in the electronic spectrum. Here we show how to disentangle them experimentally in the iron superconductors with one Fe plane per unit cell. Although the splitting of the low energy doublet at the Brillouin zone center ($\Gamma$-point) can be due to either the spin-orbit coupling or the nematic order, or both, the degeneracy of each of the doublet states at the zone corner ($M$-point) is protected by the space group symmetry even when spin-orbit coupling is taken into account. Therefore, any splitting at $M$ must be due to lowering of the crystal symmetry, such as due to the nematic order. We further analyze a microscopic tight-binding model with two different contributions to the nematic order: $d_{xz}/d_{yz}$ onsite energy anisotropy and the $d_{xy}$ hopping anisotropy. We find that a precise determination of the former, which has been widely used to characterize the nematic phase, requires a simultaneous measurement of the splittings of the $\Gamma$-point doublet and at the two low-energy $M$-point doublets. We also discuss the impact of twin domains and show how our results shed new light on ARPES measurements in the normal state of these materials.

Microstructure change and deuterium permeation behavior of the yttrium oxide coating prepared by MOCVD

Deuterium permeation measurements and microstructure analysis on yttrium oxide coating deposited by metal organic chemical vapor deposition (MOCVD) were studied. The composition and microstructure of the coating can be adjusted by tuning sublimation temperature and deposition temperature. It is found that the coating sublimated at 150 °C and deposited at 600 °C possesses compact surface morphology with no pinholes or cracking was observed. Moreover, the oxygen/yttrium ratio corresponding well to the stoichiometric Y2O3 was observed by X-ray photoelectron spectroscopy (XPS) with no moving of Y3d binding energy doublet peaks and O1s binding energy peak at different depth throughout the coating. The permeation properties of coatings depended much on the microstructure. The coating sublimated at 150 °C and deposited at 600 °C exhibits the best permeability property with PRF values 412–244 at 873–973 K. However, a permeability drop, especially for the 800 °C deposited coating was observed. It was believed that the obvious increase of pinhole and crack density caused the increase of deuterium permeability. Furthermore, the existence of (Fe,Cr)2O3, forming a grid structure in the natural oxide layer of stainless steel, increases its hydrogen permeability.

Investigation of optical properties of annealed aluminum phthalocyanine derivatives thin films

Semiconducting molecular materials based on aluminum phthalocyanine chloride (AlPcCl) and bidentate amines have been successfully used to prepare thin films by using a thermal evaporation technique. The morphology of the deposited films was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Studies of the optical properties were carried out on films deposited onto quartz and (100) monocrystalline silicon wafers and films annealed after deposition. The absorption spectra recorded in the UV–vis region for the as-deposited and annealed samples showed two absorption bands, namely the Q- and B-bands. In addition, an energy doublet in the absorption spectra of the monoclinic form at 1.81 and 1.99eV was observed. A band-model theory was employed in order to determine the optical parameters. The fundamental energy gap (direct transitions) was determined to be within the 2.47–2.59 and 2.24–2.44eV ranges, respectively, for the as-deposited and annealed thin films.

Photochemistry of trans-Cr(cyclam)(ONO)2+, a Nitric Oxide Precursor

Experimental and density functional theory (DFT) studies are described that are focused on outlining the reactivity of the known photochemical nitric oxide precursor trans-Cr(cyclam)(ONO)(2)(+) ("CrONO", cyclam = 1,4,8,11-tetrazacycltetradecane). Studies in both aerated and deaerated aqueous media are described as are the roles of both the oxidant O(2) and a reductant such as glutathione in trapping the apparent Cr(IV) photoreaction intermediate trans-Cr(cyclam)(O)(ONO)(+). Also reported and characterized structurally is the Cr(V) product of long-term photolysis in the absence of reducing agents, the trans-dioxo species [trans-Cr(cyclam)(O)(2)](ClO(4)). Photosensitization experiments indicate that at least a significant fraction of the reaction occurs from the lowest energy doublet excited state(s). Lastly, cell culture experiments demonstrate that CrONO has little or no acute toxicity either before or after photolysis.

Copper formal oxidation states above +1 in organometallic chemistry: the possibility of synthesizing cyclopentadienylcopper chlorides by oxidative addition reactions

Although organometallic compounds of Cu(I) have been known for some time, including cyclopentadienyl derivatives of the type CpCuL (Cp = η5-cyclopentadienyl ligand; L = phosphine or CO), organometallic compounds of copper in higher formal oxidation states are essentially unknown except for a few alkylcopper(III) and allylcopper(III) derivatives, only stable at very low temperatures. Theoretical studies on the cyclopentadienyl derivatives Cp2Cu2Cl n (n = 1, 2, 3) indicate a preference for structures with terminal Cp rings and bridging Cl atoms up to a maximum of two of the latter. However, Cp2Cu2Cl n (n = 1, 2, 3) structures with bridging Cp rings are found at only slightly higher energies. The lowest energy doublet mixed Cu(II/III) oxidation state Cp2Cu2Cl3 structure with a single bridging Cl atom can be formally derived from the lowest energy doublet Cu(I/II) mixed oxidation state Cp2Cu2Cl structure by oxidative addition of Cl2.

A discrete finite-dimensional phase space approach for the description of Fe8 magnetic clusters: Wigner and Husimi functions

A discrete quantum phase space formalism is used to discuss some basic aspects of the spin tunnelling which occurs in Fe8 magnetic clusters by means of Wigner functions as well as Husimi distributions. Those functions were obtained for sharp angle states and symmetric combinations of the lowest energy doublet—the particular tunnelling energy doublet—with the application of an external magnetic field. The time evolution of those functions carried out numerically allows one to extract valuable information about the dynamics of the states under consideration, in particular, the coherent oscillations associated with the particular energy doublet.

Theoretical study of the electronic structure of MCH2+(M=Fe,Co,Ni)

State of the art coupled cluster (CC) methods are applied to accurately characterize the ground state electronic structure and photoelectron spectra of transition metal carbene ions MCH(2) (+) (M=Fe, Co, and Ni). The geometries and energies of the lowest energy quartet, triplet, and doublet electronic states as well as several low-lying vertical excitation energies of FeCH(2) (+), CoCH(2) (+), and NiCH(2) (+) are reported. The excitation energies are computed using the equation-of-motion CC and for states of different symmetries, by the energy differences of single reference ground and excited states (Delta-CC). The latter employ several reference states; the unrestricted Hartree-Fock, restricted open shell Hartree-Fock, and unrestricted Kohn-Sham. We conclude that the (2)A(1) electronic ground state of NiCH(2) (+) is separated by about 30.0 kJ/mol from the next highest state, and the lowest (4)B(1) and (4)B(2) states of FeCH(2) (+) as well as the (3)A(2) and (3)A(1) states of CoCH(2) (+) are nearly degenerate. The presence of metal-pi*(MCH(2)) charge transfer states with significant oscillator strengths in the visible/near-UV energy domain of the theoretical spectra of FeCH(2) (+) and CoCH(2) (+) are at the origin of the photofragmentation of these compounds observed after irradiation between 310 and 360 nm.

Reaction of the ground-state Al( 2P) with silane: Examination of the potential energy surfaces for complexation, insertion and interconversion

A route of formation of SiH 3AlH radical via insertion of the ground-state Al( 2P) into SiH 4 and subsequent rearrangements to various primary insertion product isomers including more stable SiH 2AlH 2 radical are predicted from the ab initio single-reference CCSD(T) and multi-reference MRMP2 calculations. For the insertion reaction, the lowest energy doublet ( 2A′) potential energy surface is studied within C s symmetry. Special attention is paid to the weakly bound Al⋯SiH 4 complexes formed in the initial stage of the reaction. The results presented are of relevance to recent matrix studies on reactivity of the Al/SiH 4 system.

Coherent spin dynamics in semiconductor quantum dots

The anisotropic exchange interaction (AEI) between electrons and holes is shown to play a central role in quantum dots (QDs) spin dynamics. In neutral QDs, AEI is at the origin of spin quantum beats observed under resonant excitation between the lowest energy doublet of linearly dipole-active eigenstates. In negatively charged QDs, AEI is at the origin of QD emission with opposite helicity to the optic al excitation, under non-resonant excitation conditions. Finally, the possibility of leaving a spin information in the system after recombination of the photo-injected electron-hole pair is discussed with respect to the type and the level of the doping. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

X-ray photoelectron spectroscopy studies of the electrochemically n-doped state of a conducting polymer

X-ray photoelectron (XPS) and UV photoelectron (UPS) spectroscopies were used to characterize the electrochemically n- and p-doped states of poly (3-(4-fluorophenyl) thiophene), PFPT. The polymer was electrochemically grown on platinum electrode from the corresponding monomer. The polymer was characterized by cyclic voltammetry in an electrochemical cell that was attached to the antechamber of the spectrometer in order to avoid as much as possible exposure to ambiant air since the n-doped state is very air and water sensitive. UPS was used to evaluate the position of the Fermi level of the doped PFPT’s which allows for the determination of their work functions. The work functions of p- and n-doped PFPT are 4.3 and 2.6 eV, respectively. The S 2p core level spectrum of the n-doped polymer shows a main doublet at absolute binding energies of about 167.6 (2p 3/2) and 168.9 (2p 1/2) eV and a second doublet at lower binding energy which disappears upon oxidation to the p-doped state and is only observed for the reduced n-doped polymer. The presence of this low binding energy doublet can be explained by a higher charge localization for the n-doped state relative to the p-doped state and is consistent with the lower conductivity (by a factor of about 10) of the former. XPS was also used to investigate ion-exchange during redox switching of polymers and evaluate the doping levels of polymer. In most cases, the later values were found to be in relatively good agreement with those computed from the electrochemical data.

Reduced dimensionality quantum calculations of acetylene↔vinylidene isomerization

The isomerization of acetylene to vinylidene is examined in four degrees of freedom using a full dimensional potential. Fifteen hundred vibrational wave functions and eigenvalues that extend roughly 1500 cm−1 above the isomerization threshold are calculated using C2–H2 diatom–diatom Jacobi coordinates. Eigenfunctions of the four degree-of-freedom Hamiltonian are obtained using a series of truncation/recoupling procedures that begins with the eigenfunctions of a two degree-of-freedom Hamiltonian. The double-well nature of the isomerization is clear in these calculations and is exploited to divide the eigenfunctions into symmetric and antisymmetric groups. The lowest energy doublet states of vinylidene at two levels of dimensionality reduction indicate a splitting of the order of a wave number. Franck–Condon factors between these molecular eigenstates and a model, ground state vibrational wave function for the vinylidene anion are calculated to simulate the photodetachment spectrum of the vinylidene anion.

A Potential Energy Surface for the Electronic Ground State of H2Te Derived from Experiment

We report here the determination of a new potential energy surface for the electronic ground state of the H2Te molecule by fitting to an extensive set of very recent experimental spectroscopic data (see J.-M. Flaud, P. Arcas, H. Bürger, O. Polanz, and L. Halonen,J. Mol. Spectrosc.183,310–335 (1997), and references therein) by means of the MORBID (Morse Oscillator Rigid Bender Internal Dynamics) computer program. The fitting to all 1111 input data (involving rotation–vibrational states withJ≤ 10) had a standard deviation of 0.18 cm−1and was obtained by varying 14 parameters. With the new potential energy function, the rotation–vibration energies of H2130Te have been calculated with the MORBID program. In particular, we have calculated the rotational energy manifolds forJ≤ 40 in the lowest vibrational states. Compared to previous potential energy functions for H2Te, the new function has substantially improved the reproduction of the rotational spacings in the excited vibrational states. An important aim of the present work is the further characterization of the anomalous “fourfold cluster effect” (i.e., the formation of four-member groups of nearly degenerate rotation-vibration energies at high rotational excitation) exhibited by the energy levels of H2Te. Comparison of our theoretical results with the experimental results of J.-M. Flaud, M. Betrencourt, P. Arcas, H. Bürger, O. Polanz, and W. J. Lafferty (1997,J. Mol. Spectrosc.182,396–420) provides conclusive evidence for the existence of so-called Type II clusters (clusters formed by coalescence of two energy doublets belonging to two different vibrational states) in the ν1/ν3vibrational states of H2130Te.

Two-loop renormalization group analysis of supersymmetric SO(10) models with an intermediate scale

Two-loop evolutions of the gauge couplings in a class of intermediate-scale supersymmetric SO(10) models including the effect of third generation Yukawa couplings are studied. The unification scale, the intermediate scale and the value of the unification gauge coupling in these models are calculated and the gauge boson mediated proton decay rates are estimated. In some cases the predicted proton lifetime turns out to be on the borderline of experimental limit. The predictions of the top quark mass, the mass ratio m b ( m b )/ m τ ( m τ ) from the two-loop evolution of Yukawa couplings and the mass of the left-handed neutrino via a see-saw mechanism are summarized. The lower bounds on the ratio of the VEVs of the two low energy doublets (tanβ) from the requirement of the perturbative unitarity of the top quark Yukawa coupling up to the grand unification scale are also presented. All the predictions have been compared with those of the one-step unified theory.

Resonant tunneling times in superlattice structures

We present a rigorous and convenient approach for estimating the resonant states from the pole of the scattering matrix (reflection coefficient) in the complex energy plane and for determining the resonant tunneling time from the spacing of the energy doublets arising at resonance. The numerical calculation is much faster than numerical integration of the Schrödinger equation. When we apply this method to the coupling of two identical quantum wells, it is shown that the usual and naive estimation of resonant tunneling time through the Wentzel-Kramers-Brillouin method is invalid.

Theory of a single Oxygen hole propagating in Sr2CuO2Cl2: the spin of the quasiparticles in CuO2 planes

Recent photoemission experiments have measured E vs. k for a single hole propa- gating in antiferromagnetically aligned Sr_2CuO_2Cl_2. Comparisons with (i) the t - t' - J model, for which the carrier is a spinless vacancy, and (ii) a strong-coupling version of the three-band Emery model, for which the carrier is a S = 1/2 hole moving on the Oxygen sublattice, have demonstrated that if one wishes to describe the quasiparticle throughout the entire first Brillouin zone the three-band model is superior. Here we present a new variational wave func- tion for a single Oxygen hole in the three-band model: it utilizes a classical representation of the antiferromagnetically ordered Cu-spin background but explicitly includes the quantum fluctuations of the lowest energy doublet of the Cu-O-Cu bond containing the Oxygen hole. We find that this wave function leads to a quasiparticle dispersion for physical exchange and hopping parame- ters that is in excellent agreement with the measured ARPES data. We also obtain the average spin of the Oxygen hole, and thus deduce that this spin is only quenched to zero at certain wave vectors, helping to explain the inadequacy of the t - t' - J model to match the experimentally observed disper- sion relation everywhere in the first Brillouin zone.