Die Anregung von Rb+ in einem Kryptongitter durch die plötzliche Zentralfeldänderung beim β-Zerfall von Kr85

After theβ-decay of Kr⁸⁵ in solid Krypton the Rb⁺-ion, resulting from this decay, is excited in 4p⁵ 5p(J=0)-states with a certain probability. The photon-spectrum, due to dipole-transitions from these excited states, selected with narrow-band-filters and measured in coincidence with the emittedβ-particles, shows narrow bands (“lines”) and broad bands. The “lines” are not shifted with respect to the atomic Rb⁺-lines, whereas each broad band can be interpreted as a component of each “line”, being shifted about 800 cm^?1 to the blue end of the spectrum. The measured lifetime of the excited states is (7.5±0.5) ns in the “lines” and (5±0.5) ns in the bands, the measured excitation-probability is (8±1) · 10^?2 perβ-decay. A calculation of the magnitude of the spectral shift and the excitation-probability with the LCAO-approximation is made under the following assumptions: the “lines” are due to Rb⁺-ions on regular crystal-sites; the shifted bands are caused by Rb⁺-ions, trapped at octaedral interstitial-sites, after being displaced from their original regular crystal-sites by theβ-recoil. A comparison between the experimental and calculated values confirms these assumptions.     

Intrinsic irreversibility of Kolmogorov dynamical systems

We give the mathematical details and various extensions of the results stated in previous work of Courbage and Prigogine. “Intrinsic random systems” are deterministic and conservative dynamical systems for which we can associate two dissipative Markov processes through a one-to-one “change of representation”, the first leading to equilibrium for t→+∞ and the second for t→-∞. The microscopic formulation of the second principle of thermodynamics permits to lift the degeneracy by the exclusion of all states that do not approach equilibrium for t→+∞. The set of admitted initial conditions $\text{D}$⁺ is then characterized by a non-equilibrium entropy functional which is infinite for rejected initial states and takes finite values for admitted initial conditions. Thus, rejected initial states correspond to an infinite amount of information. To realize this selection rule we consider general probability measures on phase space that are not necessarily absolutely continuous and we extend the theory of transition to Markov processes to such measures. Owing to the non-invariance of $\text{D}$⁺ under the time inversion, the evolution of these states in the new representation can only be given by one of the two possible Markov processes.     

Planar rings in glasses

An energy minimization argument is used to predict that small order rings of bonds are likely to be planar in many glasses. The 606 and 495 cm^-1 Raman “defect” lines in fused silica are then shown to be consistent with small concentrations (?1%) of planar 3-fold and 4-fold rings, respectively. The argument predicts this form of intermediate range order at larger concentrations in several glasses, including 3-fold planar rings in B₂O₃, while it predicts no planar rings in other glasses, including ZnCl₂.     

On the Energy of a “One-Dimensional” Two-Electron Atom

Based on the perturbation theory and variational method long known for a “three-dimensional” atom, the ground and first excited state energies are calculated for a “one-dimensional” two-electron atom in the “one-dimensional ortho-helium” configuration, which can be obtained experimentally in principle, as has been already done for a Na Bose condensate, or produced in a super strong magnetic field B ? (2α)²B₀ (B₀ = m²c³/e? ≈ 4.41 × 10¹³ G). The “screening constant” σ for this atom in the ground and excited states was about 0.20 and 0.17, 0.18, respectively, depending on the relative parity PP' of the electronic states, which is somewhat smaller than in “two-dimensional” and “three-dimensional” variants (in these cases, this constant in the ground state is almost the same and about 0.3). The frequencies of the main spectral lines of a “onedimensional” He atom representing a doublet split over the relative parity PP' are found. The presence of the close lines of this doublet in the emission spectrum of magnetars at frequencies ω_{1, 2} ≈ {1.15; 1.17}α²(c/λC) (α = e²/?c, λ_C =?/mc) corresponding to the “one-dimensional ortho-helium” would suggest the existence of a superstrong magnetic field in such astrophysical objects.     

Role of anharmonicities and nonlinearities in heavy ion collisions A microscopic approach

Using a microscopic approach beyond RPA to treat anharmonicities, we mix two-phonon states among themselves and with one-phonon states. We also introduce nonlinear terms in the external field. These nonlinear terms and the anharmonicities are not taken into account in the “standard” multiphonon picture. Within this framework we calculate Coulomb excitation of ²⁰⁸Pb and ⁴⁰Ca by a ²⁰⁸Pb nucleus at 641 and 1000 MeV/A. We show with different examples the importance of the nonlinearities and anharmonicities for the excitation cross section. We find an increase of 10% for ²⁰⁸Pb and 20% for ⁴⁰Ca of the excitation cross section corresponding to the energy region of the double giant dipole resonance with respect to the “standard” calculation. We also find important effects in the low-energy region. The predicted cross section in the DGDR region is found to be rather close to the experimental observation.     

Low activation energies in superionic glasses in the 4.2–77 K temperature region

The peaks in the ultrasonic attenuation observed in AgI-doped superionic glasses at temperatures higher than 77 K have always been explained in terms of classical, thermally activated, relaxation processes due to silver ions which are mobile in the glassy matrix. Here we complete an ultrasonic study with the loss characteristics and sound velocity in “binary” (Ag₂O·nB₂O₃) and “ternary” [(AgI)_x(Ag₂O·nB₂O₃) _{1 − x}] glasses in the 4.2–77 K temperature region. In such a way we obtain useful information about defects having low activation energy.     

Work function measurements on germanium by thermionic emission

In the present paper, we report the results of experiments carried out to determine the effect of surface states on the work function of intrinsic, germanium crystals. This investigation is realised by using the Thermionic Emission Theory at the intrinsic temperature range T (from 900 to 1050 K). The “apparent work function” φ¹, obtained from the experimental ln(i_sT²) versus 1/T curves, is found different from the Richardson-Dushman equation one: “the true work fucntion” φ. This difference is mainly due to the work function and electron reflection coefficient dependence on temperature. φ is deduced from φ¹ and from RD modified equation taking into account the semiconductor case. The value of φ varies with T: from 3.97 to 4.16 eV. These results are compared with those obtained, by several authors, using other techniques. We present an analysis of these results taking into consideration the effect of surface states shifts on the surface barrier height, and on the work function consequently.     

Quadratic corrections to three‐point functions

Following the recent progress on the calculation of three‐point correlators with two “heavy” (with large quantum numbers) and one “light” states at strong coupling, we compute the logarithmic divergent terms of leading bosonic quantum corrections to correlation functions with “heavy” operators corresponding to simple string solutions in AdS₅ × S⁵. The “light” operator is chosen to be the dilaton. An important relation connecting the corrections to both the dimensions of “heavy” states, and the structure constants is recovered.     

The density of states method and the velocity of sound in hot QCD

We present an initial study of the thermodynamics of hot lattice QCD using the “density of states” method, which we describe in detail. The raw data were generated from a Monte Carlo simulation of pureSU(3) gauge theory on 8³×N _t lattices, withN _t =2,4,8, at several values of the gauge coupling β. These data, taken at up to eight values of β, are then used to reconstruct the “density of states” as a function of the action and one additional observable. When combined with the proper Boltzmann weight this yieldscurves of quantities of interest as functions of the coupling constant β. These curves then yield the equation of state in a range of temperature, and the corresponding velocity of sound is obtained through appropriate derivatives. We also discuss in detail the errors, limitations, and advantages of the density of states method in its general application to QCD.     

Single-neutron states at high spins in ytterbium nuclei: Evidence for the quenching of static neutron pair correlations

The decay schemes of ^167,168,169Yb are established to the largest angular momenta yet known in stably-deformed rare-earth nuclei using the ¹²⁴Sn(⁴⁸Ca,3–5n) reaction. The systematics of the resulting spectrum of single-neutron states in these and neighbouring Yb isotopes at large and small angular momenta are discussed with regard to that expected in the presence and absence of static neutron-pair correlations. This comparison, together with cranking-model and “gauge-space” analyses, provides evidence for the effective disappearance of static neutron-pair correlations for the odd-N isotopes at ?ω ? 0.38 MeV. A composite empirical spectrum of single-neutron states is constructed for the “unpaired” regime and is compared with cranking calculations.     

Vibrational anomalies and marginal stability of glasses

The experimentally measured vibrational spectrum of glasses strongly deviates from that expected in Debye’s elasticity theory: The density of states deviates from Debye’s ω² law (“boson peak”), the sound velocity shows a negative dispersion in the boson-peak frequency regime, and there is a strong increase in the sound attenuation near the boson-peak frequency. A generalized elasticity theory is presented, based on the model assumption that the shear modulus of the disordered medium fluctuates randomly in space. The fluctuations are assumed to be uncorrelated and have a certain distribution (Gaussian or otherwise). Using field-theoretical techniques one is able to derive mean-field theories for the vibrational spectrum of a disordered system. The theory based on a Gaussian distribution uses a self-consistent Born approximation (SCBA),while the theory for non-Gaussian distributions is based on a coherent-potential approximation (CPA). Both approximate theories appear to be saddle-point approximations of effective replica field theories. The theory gives a satisfactory explanation of the vibrational anomalies in glasses. Excellent agreement of the SCBA theory with simulation data on a soft-sphere glass is reached. Since the SCBA is based on a Gaussian distribution of local shear moduli, including negative values, this theory describes a shear instability as a function of the variance of shear fluctuations. In the vicinity of this instability, a fractal frequency dependence of the density of states and the sound attenuation ∝ ω^1+a is predicted with a ? 1/2. Such a frequency dependence is indeed observed both in simulations and in experimental data. We argue that the observed frequency dependence stems from marginally stable regions in a glass and discuss these findings in terms of rigidity percolation.     

The G-central decomposition of states of statistical systems in the algebraic and in the operational description

We consider a group of automorphisms of a compact convex set X. Using simplical measure techniques we find a decomposition of points of X into “G-primary” points. The decomposition of Guichardet and Kastler for quasi-invariant states of a separable C¹- algebra is generalized.     

Discovery of a linear relationship between the glass transition temperature of oxide glasses and the quadrupole splitting of the Fe3+ substituted for the individual network—forming cations (NWF)

⁵⁷Fe-Mössbauer and DTA study of several oxide glasses has revealed that there exists a linear relationship between Tg(glass transition temperature) and δ (quadrupole splitting) of Fe³⁺, which is substituted for individual NWF(network former), e.g., V⁵⁺, Ti¹⁺, Te¹⁺, Al³⁺, Ca³⁺ and B(III). The linear relationship named “Tg-δ rule” is expressed by Tg=aδ+b, which indicates that Tg of oxide glasses is closely correlated to the asymmetry or local distortion of NWF-oxygen polyhedra. The “Tg-δ rule” also holds for the γ-ray irradiated tellurite glasses and for the glass-ceramics of calcium aluminate.     

Pseudoscalar mesons in the c-c and b-b systems

It is shown that the pseudoscalar η_c and “η_c” (η_b and “η_b”) with M ≈ 2.80 and 3.51 GeV (9.17 and 9.88 GeV) can be predicted by using the radial mixing model, where the “η_c” and “η_b” are the excited 0^- states in the $\text{c-}\text{c}$ and $\text{b-}\text{b}$ systems, respectively, and the former would correspond to the observed 0^- meson with M ≈ 3.45 GeV in charmonium.     

Quasi-Bound States of Two Magnons in the Spin-1/2XXZ Chain

We study two-magnon Bethe states in the spin-1/2 XXZ chain. The string hypothesis assumes that complex rapidities of the bound states take special forms. It is known, however, that there exist “non-string states,” which substantially disagrees with the string hypothesis. In order to clarify their nature, we study the large-N behavior of solutions of the Bethe-Ansatz equations to obtain explicit forms of typical Bethe states, where N is the length of the chain, and apply the scaling analysis (the multifractal analysis) to the Bethe states. It turns out that the non-string states contain “quasi-bound” states, which in some sense continuously interpolate between extended states and localized states. The “quasi-bound” states can be distinguished from known three types of states, i.e., extended, localized, and critical states. Our results indicate that there might be a need to reconsider the standard classification scheme of wavefunctions.     

Vacancy induced changes in the electronic structure of titanium carbide—I. Band structure and density of states

Results of a self-consistent “Augmented Plane Wave” (APW) band-structure calculation are presented for substoichiometric titanium carbide with 25% vacancies on the carbon sublattice sites (TiC_{0 75}) assuming a model structure with ordered vacancies Comparison with an earlier APW study on stoichiometric TiC reveals that the carbon vacancies induce two pronounced peaks in the density of states (DOS), 0.4 eV below and 0.8 eV above the Fermi energy E_γ, thus forming electronic states in a region where the DOS for stoichiometric TiC exhibits a minimum So-called “vacancy states” with an important amount of charge on the vacancy site are found to be derived from Ti 3d states extending into the vacancy muffin tin sphere An angular momentum decomposition with respect to the center of the vacancy muffin tin sphere shows that the s character predominates for the occupied and the p character for the unoccupied “vacancy states” The theoretical findings explain features near E_γ, observed in recently published X-ray emission spectra Furthermore, we find a slight increase of electronic charge in the carbon muffin tin spheres as compared with stoichiometnc TiC.     

Electron energy loss for two transition metal-transition metal glasses

Electron energy loss data are reported for metallic glasses Fe_0.92Zr_0.08 and Ni_0.5Zr_0.5. These data document the sensitivity of the spectra to sample thickness and suggest studies of metallic glasses require samples that are nearly $\text{1}\text{2}$ an order of magnitude “thinner” than crystalline alloys. Each electron energy loss spectrum has a dominant loss near 23–25 eV which is similar to the loss function of the pure 3-d metal. This lack of a shift in the location of the dominant loss challenges any simple model of plasmon behavior. The M₂₃ core losses are visible in the “thinner” samples and, in agreement with earlier studies on metal-metalloid glasses, no measureable chemical shift is observed.     

X-ray and UV photoelectron-spectroscopic studies of pyridine adsorbed on evaporated nickel and palladium in the temperature range 140–385 k

The states of pyridine adsorbed on evaporated nickel and palladium films have been investigated as a function of temperature in the range 140–385 K by means of X-ray and UV photoelectron spectroscopy. At ～ 140 K, pyridine “N-bonded” on the metal surfaces gives C 1s and N 1s peaks whose binding energies are very close to those for condensed pyridine and “N-bonded” pyridine on pre-oxidized nickel. The high-lying valence orbitals, 2b₁ (π) and 1a₂ (π) + 7a₁ (n), of pyridine show shifts similar to those for the “N-bonded” molecule on pre-oxidized nickel. At ～ 290 K, “π-bonded” pyridine shows large shifts in the C 1s and N 1s peaks and in the high-lying valence orbitals, as observed for “π-bonded” benzene on nickel. The assignments of the adsorbed states are supported by work-function change data. A large proportion of pyridine converts from the “N-bonded” to the “π-bonded” form between 220 and 290 K. Formation of “α-pyridyl” is suggested at ～ 375 K on nickel.     

QCD studies and discoveries with e + e − colliders and future perspectives

Observations of new charmonium(-like) and bottomonium(-like) states (sometimes refered to as “XYZ” states) at e ^?+? e ^??? colliders have changed our picture of quarkonia systems as QCD bound states. Potential models with a linear confinement ansatz, which were able to predict many conventional states with an accuracy of ～1 MeV, absolutely fail in describing many of the new states. Symmetries play an important role e.g. in the determination of the quantum numbers (such as charge conjugation in the radiative decays) or in trying to explain surprising properties such as isospin violation.