Extra Transitions Research Articles

Coupled mesoscopic superconductors: Ginzburg-Landau theory

The magnetic coupling between two concentric mesoscopic superconductors with nonzero thickness is studied using the nonlinear Ginzburg-Landau theory. We calculated the free energy, the expelled field, the total field profile, the Cooper-pair density, and the current density distribution. By putting a smaller superconducting disk or ring in the center of a larger ring, the properties change drastically. Extra ground-state transitions are found, where the total vorticity stays the same, but the vorticity of the inner superconductor changes by 1. Due to the magnetic coupling, the current in the external ring exhibits extra jumps at the transition fields where the vorticity of the inner superconductor changes. In this case, for certain temperatures, re-entrant behavior and switching on and off of the superconducting behavior of the rings are found as a function of the magnetic field. A $H\ensuremath{-}T$ phase diagram is obtained for the situation where the inner ring has a higher critical temperature than the outer ring. An analytic expression for the magnetic coupling is obtained for thin rings and extreme type-II superconductors.

Parking Can Get You There Faster: Model Augmentation to Speed up Real-Time Model Checking

We present an approximation technique, that can render real-time model checking of safety and universal path properties more efficient. It is beneficial, when loops lead to repetition of control situations. Basically we augment a timed automata model with carefully selected extra transitions. This increases the size of the state-space, but potentially decreases the number of symbolic states to be explored by orders of magnitude.We give a formal definition of a timed automata formalism, enriched with basic data types, hand-shake synchronization, urgency, and committed locations. We prove by means of a trace semantics, that if a safety property can be established in the augmented model, it also holds for the original model.We extend our technique to a richer set of properties, that can be decided via a set of traces (universal path properties). In order for universal path properties to carry over to the original model, the semantics of the timed automata formalism is formulated relative to the applied augmentation.Our technique is particularly useful in systems, where a scheduler dictates repetition of control over elapsing time. As a typical example we mention translations of LEGO® RCX™ programs to Uppaal models, where the Round-Robin scheduler is a static entity. We allow scheduler and associated tasks to “park”, until some timing or environmental conditions are met.We apply our technique on a brick-sorter model for a safety property and report run-time data.

The Spectrum of Hot Water: Rotational Transitions and Difference Bands in the (020), (100), and (001) Vibrational States

Analysis of the hot H216O spectrum, presented by Polyanskyet al.(1996,J. Mol. Spectrosc.176,305–315), is extended to higher vibrational states. Three hundred thirty mainly strong lines are assigned to pure rotational transitions in the (100), (001), and (020) vibrational states. These lines, which involve significantly higher rotational energy levels than were known previously, are assigned using high-accuracy variational calculations. Transitions in (020) are assigned up toKa= 18, compared with the maximumKaof 10 known previously. Crossings of vibration–rotation energy levels result in the observation of extra intensity-stealing transitions. In particular, this leads to the assignment of (020)–(100) and (100)–(020) rotational difference band transitions in addition to the conventional pure rotational lines in (020) and (100) states. These extra lines increase the number of transitions and they are likely to complicate the pure rotational water spectrum in higher excited vibrational states to an even greater extent. A few lines from our previous work on the pure rotational spectrum of hot water in the (000) and (010) vibrational states are also reassigned and some further assignments are made.

Strong coupling effects in 2D J, δ Spectra: An application for the determination of the conformational isomers of some 1,4 disubstituted dioxanes

When strong proton–proton coupling is present, a projection of the tilted two-dimensional J, δ (J-resolved) spectrum frequently produces one or more extra lines, i.e., there are more lines in the projection than there are protons in the molecule. Contrary to popular belief, these lines are not “extraneous nuisances.” Instead, they may contain a wealth of information that can be of value for the determination of structural isomers. This article provides a brief introduction to the theory of these spectra and examines the origin as well as the practical properties of these extra transitions. Two important properties are: (a) in the untilted spectrum, the extra transitions have F2 frequencies that are equal to those of the normal transitions; and (b) they lie on a line that is midway between the lines that are formed by the normal transitions. As a practical application of the usefulness of these properties, this article presents the strategy used to identify several structural isomers of 2,5- and 2,6-disubstituted 1,4-dioxanes. All of the possible isomers were identified, including the separation of the “frozen” isomers from the equilibrating ones, and the separation of the 2,5- from the 2,6-disubstituted ones. The identification was achieved by measuring the coupling constants between the ring protons, and then using (a) the Karplus relationship to determine whether the substituent was axial or equatorial, and (b) the well-known planar-zigzag, or “W,” coupling to determine whether the substituents were both adjacent to only one of the ring oxygen atoms (the 2,6-isomer) or whether each was situated adjacent to only one ring oxygen atom (the 2,5-isomer). ©1997 John Wiley & Sons, Inc. Concepts Magn Reson 9: 359–384, 1997

The absorption spectrum of C2H2 around ν1 + ν3: energy standards in the 1.5 μm region and vibrational clustering

We have recorded the Fourier transform absorption spectrum of acetylene, C2H2, at high resolution, around 6500 cm−1. The positions of the strongest rovibrational lines are measured with respect to the rovibrational lines in 3-0 of CO. They provide secondary calibration standards in that range with an accuracy of 3 × 10−4 cm−1. The rotational analysis of the data gives evidence of five vibrational levels of [Formula: see text] symmetry, in addition to the bright combination level (1010000). This is demonstrated to strictly fit the predicted anharmonic resonance pattern in that region, which permits the vibrational assignment of those extra transitions. Study of the relative intensities of the reported vibrational transitions suggests the need to include new quartic anharmonic couplings. This is supported by the rovibrational analysis of the cold bands around 8500 cm−1, involving the (1110000) bright level, which is also presented.

Molecular beam stimulated emission pumping spectroscopy of propynal

Stimulated emission pumping (SEP) experiments were performed on propynal (H–C≡C–CHO). The SEP spectra probed the overtones of the pure C=O stretch (ν4) and a combination of the C=O stretch with the C≡C–C bend (ν9). Term energies for J≤8, K≤2 of the vibrations 42, 43, 44, 45, 4391 as well as two unidentified perturbing vibrational states were obtained. The SEP spectra show simple rotational structure that is assignable by means of a near prolate asymmetric top model. Rotational constants were obtained for all the vibrational states measured. Spectroscopic perturbations are observed for ν4=2,4,5 as either anomalous rotational constants, anomalous energy level shifts, or as extra spectral transitions. Complex state mixing is not observed at the current spectroscopic resolution (0.04 cm−1) even though vibrational state densities as high as 400 states per cm−1 were probed. The propynal SEP results are compared to other SEP experiments on aldehyde containing molecules and inferences are made.

Pattern dependent overwrite on thick media

Overwrite measurements on thick media as a function of the recorded data pattern and record current level are presented. Two recording methods are addressed, full wave NRZI recording and double density NRZI (D/sup 2/NRZI). The overwrite using NRZI recording is poor on thick media as low density signals are recorded deep into the media. Significant improvement is seen when extra higher density transitions are introduced between data ONEs for the D/sup 2/-NRZI method which restricts the recording depth of low frequency components. However, the residual signal at the fundamental frequency of the data pattern is higher for long strings of ZEROs between ONEs than short strings, which is attributed to the reproduce head response.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reflectance spectra of β -, θ -, and κ-(BEDT-TTF) 2I 3, and β″- and β′-(BEDT-TTF) 2ICl 2: Relation between the inter-band transition and the dimeric structure

The polarized reflectance spectra of the single crystals of the title compounds were measured at room and low temperatures. The correlation was found between the appearance of the extra electronic transitions overlapped on the Drude-tail and the dimeric arrangement of BEDT-TTF. From this relation, this extra transition was assigned to the inter-band transition between the split bands due to the strong dimeric interaction. The Drude parameters were determined by analyzing the low-temperature spectra taking account of the inter-band transition.

Excitonic transitions of ordered layers of Xe on ag(111) and Al(111): A low-energy EELS study

We present the results of low-energy electron energy loss spectroscopy (EELS) studies of the lower excitonic transitions of Xe thin films on single crystal Ag(111) and Al(111) surfaces. We find that the spectra of cold (≈20 K) deposited, disordered Xe films can be interpreted in terms of broadened atomic-like transitions. However, the spectra of ordered Xe layers. obtained upon annealing, show extra transitions with no optical counterparts. These observations are explained in terms of significant dispersion and lifting of the degeneracy of levels in ordered layers of Xe. Low-energy EELS allows transitions to the split excitonic levels involving large momentum transfer.

ESR studies of donor clusters in silicon

ESR spectra for Si:P and Si:As samples with donor concentrations ranging from 9×1016 to 5×1017/cc have been obtaines in the range 4.2K to 20K at 9 GHz. dχ″dH spectra were integrated to obtain χ″(N,T,H) allowing the determination of relative contributions from different size clusters. The ratio of integrated intensity of the outer lines to the total integrated intensity obeys Poisson statistics and yields a characteristic volume Vc for Si:P of 8.21×106Å3. A search outside the isolated donor hyperfine lines has revealed no extra transitions 0.03% of the outer hyperfine lines. A new many-electron cluster hyperfine interaction is formulated which takes account of topological disorder for larger clusters. The effect of hyperfine topological broadening and cluster-cluster interactions on the ESR line widths and shapes are considered.

Electrical conductance of crystalline TinO2n-1for n=4-9

The DC G(T) has been measured in the approximate range 4-320K for crystalline samples of the series TinO2n-1 with 4<or=n<or=9. This includes the first results reported for n=7, 8 and 9. The G(T) for n=4, 5 and 6 show qualitative differences from the behaviours reported previously, including extra transitions at 127K and 119K for n=5 and 6, respectively. Despite the homologous crystal structures and the similar transition temperatures, the G(T) for this Magneli series show few systematic trends. This implies that no single conduction mechanism dominates across the series, but for n=5, 6 and 7 the authors find evidence that quantum tunnelling and thermally activated jumping may be the dominant mechanisms over limited temperature ranges.

Determination of Nuclear Quadrupole Coupling by Simulation of EPR spectra of frozen solutions

Nuclear electric quadrupole interactions can influence EPR spectra very strongly at certain magnetic field orientations through the positions and intensities of double-spin-flip transitions. Previously, we analyzed orientation-dependent EPR spectra of magnetically dilute single crystals having 63Cu in a variety of coordination sites to obtain principal components of the quadrupole coupling tensor. The values showed a striking correlation with site geometry and electronic structure. High-symmetry, large-coordination-number sites have the largest quadrupole coupling constants. This potentially useful structural tool has been limited by its restriction to dilute single crystals. Accordingly, we report now on the importance of the quadrupole-sensitive double-spin-flip transitions in EPR spectra of frozen solutions. The X-band and Q-band spectra of some frozen solutions of copper /f-ketoenolates (with the copper isotopes in natural abundance) in more-or-less coordinating solvents had rather broad, poorly resolved features. Nevertheless, inclusion of the double-spin-flip transitions proved essential to successful stimulation of the X-band spectra. By matching computed simulations with the experimental spectra we show that these extra transitions contribute sufficiently to permit one to extract nuclear quadrupole coupling information. The resulting quadrupole coupling constants follow the expected order of solvent ligand strength and lie in between those previously found for sites of 5- and 6-coordination. Specific axial solvent coordination is implied.

Argon ion and dye laser induced MgO B1Σ +- X1Σ + and B1Σ +- A1Π photoluminescence spectra : Analysis of a3Π i ∼ X1Σ + perturbations

We have experimentally demonstrated that the electronic ground state of MgO is X 1Σ +. The lowest energy excited state was shown to be a 3Π i , for which the following constants were determined (1σ uncertainty in parentheses): T e 2623 (7) cm −1 ω e 648 (5) ω ex e 3.9 (9) B e 0.5022 (13) α e 0.0042 (8) (Pekeris' relation) A −64 (1) The a 3Π i state was observed and characterized from its perturbations of the X 1Σ + ( v X > 2) levels. These perturbations were detected in the photoluminescence from the B 1Σ + state induced by the 476.5-, 496.5-, and 514.5-nm lines of an argon ion laser. The three laser lines were shown to coincide with a total of eight strong and assignable molecular lines belonging to the B 1Σ + - X 1Σ + system of the three isotopic species 24Mg 16O, 25Mg 16O, and 26Mg 16O. The 496.5-nm line excited the less abundant 26Mg 16O species almost exclusively. Rotationally resolved photoluminescence from eight B 1Σ + ( v B , J B ) levels was observed into vibronic levels X 1Σ + ( v X = 0–7) and A 1Π ( v A = 0–8). X 1Σ + ∼ a 3Π i perturbations appeared as level shifts often accompanied by extra transitions into levels of dominants a 3Π i character; a total of 20 extra lines were assigned. A 1Π ∼ X 1Σ + perturbations were also observed, and six extra lines were assigned. Measurement of the relative intensities of B 1Σ + - A 1Π and B 1Σ + - X 1Σ + photoluminescence originating simultaneously from a single ( v B , J B ) level permitted determination of the transition moment ratio T e 2623 (7) cm −1 ω e 648 (5) ω eX e 3.9 (9) β e 0.5022 (13) α e 0.0042 (8) (Pekeris' relation) A −64 (1) The electronically excited A 1Π state was present in our Mg + N 2O flame in sufficient concentration to record the MgO B 1Σ + ← A 1Π excitation spectrum using a cw Rhodamine 6G dye laser. This observation raises the possibility of direct population monitoring of other electronically excited species in flames.

Influence of the surface on the quantum P.E.M. effect in InP

The polarized reflectance spectra of the single crystals of the title compounds were measured at room and low temperatures. The correlation was found between the appearance of the extra electronic transitions overlapped on the Drude-tail and the dimeric arrangement of BEDT-TTF. From this relation, this extra transition was assigned to the inter-band transition between the split bands due to the strong dimeric interaction. The Drude parameters were determined by analyzing the low-temperature spectra taking account of the inter-band transition.

The electron resonance of ground state triplets in liquid crystal solutions

The electron resonance spectra of two ground state triplets have been measured in the isotropic and nematic mesophase of p-azoxyanisole. The extra transitions observed when the biradicals are in the nematic mesophase are interpreted in terms of an unaveraged zero-field splitting. The nitrogen hyperfine splitting is also found to decrease in the nematic mesophase. The observation of these extra lines in the spectra provides excellent quantitative confirmation for the triplet character of these radicals. The changes in the spectra are satisfactorily accounted for using the swarm model of nematic liquid crystals.