Pions in primary cosmic rays of ultrahigh energies

In the framework of the Coleman-Glashow hypothesis of an extremely weak violation of Lorentz invariance, neutral and charged pions can be stable for energies above 10¹⁹ eV and enter into the composition of primary cosmic rays of ultrahigh energies. The kinematic exclusion of reactions of pions with relic photons is particularly important, because it allows the Greisen-Zatsepin-Kuzmin paradox to be resolved. The parameters of extensive air showers induced by primary pions calculated within the model of quark-gluon strings with allowance for the Landau-Pomeranchuk-Migdal effect and interactions of neutral pions of ultrahigh energies are not contradictory to the available data of observations. It has been shown that observations of production heights of muons with energies above 10GeV will make it possible to distinguish between primary nuclei, protons, and pions; to verify Lorentz invariance for energies above 10²⁰ eV; and to obtain a new limit on the difference between the maximum possible velocities of muons and pions (c_µ?c_π)<4×10^?26.     

Dynamics of water in binary and ternary solutions of DNA and porphyrins

The dynamics of heavy water (at 20°C) in solutions with polyanionic DNA chains and ternary systems containing DNA and negatively charged tetraphenylporphyrins has been investigated using neutron resonance spin echo in the time range t = 1?1000 ps. The diffusion dynamics has been observed in the momentum transfer range q = 1.3?1.8 Å^?1, and the relaxation rates in single-component, binary, and ternary systems are close to each other. Apart from the relaxation, the vibrational mode in the solutions has been revealed at the momentum transfer q = 1.9 Å^?1. The introduction of porphyrins into the solution (one molecule per ten DNA base pairs) has resulted in a retardation of diffusion and a considerable increase (by 5–10%) in the frequency of translational vibrations of water molecules due to the interaction with porphyrin molecules.     

A modification of Einstein–Schrödinger theory that contains both general relativity and electrodynamics

We modify the Einstein–Schrödinger theory to include a cosmological constant Λ _z which multiplies the symmetric metric, and we show how the theory can be easily coupled to additional fields. The cosmological constant Λ _z is assumed to be nearly cancelled by Schrödinger’s cosmological constant Λ _b which multiplies the nonsymmetric fundamental tensor, such that the total Λ =  Λ _z +  Λ _b matches measurement. The resulting theory becomes exactly Einstein–Maxwell theory in the limit as |Λ _z | → ∞. For |Λ _z | ~ 1/(Planck length)² the field equations match the ordinary Einstein and Maxwell equations except for extra terms which are < 10^?16 of the usual terms for worst-case field strengths and rates-of-change accessible to measurement. Additional fields can be included in the Lagrangian, and these fields may couple to the symmetric metric and the electromagnetic vector potential, just as in Einstein–Maxwell theory. The ordinary Lorentz force equation is obtained by taking the divergence of the Einstein equations when sources are included. The Einstein–Infeld–Hoffmann (EIH) equations of motion match the equations of motion for Einstein–Maxwell theory to Newtonian/Coulombian order, which proves the existence of a Lorentz force without requiring sources. This fixes a problem of the original Einstein–Schrödinger theory, which failed to predict a Lorentz force. An exact charged solution matches the Reissner–Nordström solution except for additional terms which are ~10^?66 of the usual terms for worst-case radii accessible to measurement. An exact electromagnetic plane-wave solution is identical to its counterpart in Einstein–Maxwell theory.     

Electron and electron-phonon effects in the quasi-two-dimensional molecular conductor θ-(BETS)<Subscript>4</Subscript>HgBr<Subscript>4</Subscript>(C<Subscript>6</Subscript>H<Subscript>5</Subscript>Cl): Optical studies at 300–15 K

This paper reports on a study of the polarized reflectance and optical conductivity spectra of the quasi-two-dimensional molecular conductor θ-(BETS)₄HgBr₄(C₆H₅Cl) within the 700–6500-cm^?1 region at 300–15 K and within the 9000–40 000 cm^?1 region at 300 K performed along two principal directions in the crystal plane parallel to the conducting layers of the BETS molecules. The IR spectra obtained at 300 K follow a close-to-Drude behavior, with strong broad features (1200–1400 cm^?1) due to electron-vibrational (vibronic) coupling (VC) superposed on the high Drude background. As the temperature is lowered in the range 180–80 K, in the spectra there appears a Lorentz term with ω_t=2900 cm^?1, as well as three additional VC-induced bands in the 800–1180-cm^?1 region, which disappear as the temperature is decreased further. The results obtained indicate the existence of unstable structural distortions along the two principal directions in the crystal, which are accompanied by the formation of a commensurate charge-density wave.     

Dielectric-field effect correction on i.r. band shapes in the liquid phase

The dielectric-field correction on i.r. band shape in the liquid has been studied by using the Lorentz internal field. The deformation of the band shape is inappreciable for a weak absorption band that becomes measurable only at a sample thickness larger than 10μ. The shapes of the strong singlet and doublet bands of hexafluorobenzene at 1530 cm^?1 and near 1000 cm^?1, respectively, and also of the doublet band of carbon tetrachloride near 790 cm^?1 have been measured in dilute solutions and compared with those for the pure liquid.     

Excited state dynamics in silver nanoparticles embedded in phosphate glass

Excited state dynamics in silver nanoparticles embedded in aluminophosphate glass was studied by ultrafast optical pump–probe technique. The absorption process of pump radiation and the electron–phonon relaxation on the 10^?13–10^?11 s scale were analyzed in the framework of two-temperature model. The time evolution of the light-induced transient diffraction grating shows an uncommon relaxation on the nanosecond time scale. This relaxation is assigned to phonon–phonon scattering process as well as to the energy transfer from photoexcited electronic states in glass matrix to silver nanoparticles.     

Possible mechanisms of dielectric relaxation of liquid water and calculation of the temperature dependence of the complex permittivity of water

The spectra of the complex dielectric permittivity and absorption of water (H₂O) in the frequency range 0–1000 cm^?1 are calculated for a wide temperature interval. Using the method of autocorrelation functions, the dielectric response of dipoles rotating in potential wells of three types is found. The majority of dipoles (about 90%) rotate in a deep and comparatively narrow potential well, whose profile resembles an upside-down hat. Such a potential models a molecular structure with strongly bent and/or broken hydrogen bonds. The hat model describes the complex permittivity in the low-frequency (Debye) range and in the range 300–1000 cm^?1. The remaining dipoles (～10%) execute harmonic vibrations of two types: rotational vibrations about the equilibrium direction of a hydrogen bond and translational vibrations along this direction. These types of motion yield the dielectric response in the frequency range 10–300 cm^?1. This response is described by the Lorentz lines in terms of the harmonic oscillator model and the truncated parabola model. The hat–harmonic oscillator–truncated parabola composite model provides good agreement with experimental spectra. The lifetimes of the three types of motion considered are about 10, 0.2, and 0.05 ps, respectively. They characterize (i) tetrahedral translations of molecules accompanied by their rotations, (ii) librations of dipoles in the hatlike potential well, and (iii) elastic interactions of hydrogen-bonded molecules. Based on data of independent methods of investigation, it is concluded that the temperature 300 K is a singular point with respect to the properties of liquid water.     

Experimental resolution of the retardation time spectrum in polymeric solids by a new method: Thermostimulated creep

We propose a new method for the investigation of molecular motion in polymeric solids. In a mechanical step-function experiment, we thermally stimulate the response to a constant stress. The high resolving power of this technique permits detailed study of the complex retardation modes observed in polymers. By using “fractional” loading programs it is possible to differentiate a discrete and a continuous distribution of retardation time. This technique allows us to predict the complex compliance in a very wide frequency range: 10⁴-10^?12 Hz for experiments performed between liquid nitrogen temperature and 500°K. In low-density polyethylene, we have shown the existence of a discrete spectrum of mechanical retardation times which has the same fine structure as the spectrum of dielectric relaxation times obtained from the study of depolarization thermocurrent on the same sample. The predicted variation versus temperature and frequency of the loss compliance is compared with that of the dielectric loss factor.     

Fields nonlocal in clifford space

A previously proposed field theory is quantized. The theory contains a parameter having the character of an elementary length. We fix the value of this parameter by scaling it to the weak interaction strength. It is shown that this way negative metric states are confined to a region of the order 10^?15 cm. The resulting quantum theory of interacting fields is Lorentz and gauge invariant, has a unitaryS-matrix, and is convergent.     

Ramp compression of tantalum to 330 GPa

We report on the stress–density and rate-dependent response for Ta, ramp compressed to 330?GPa with strain rates up to 5?×?10⁸?s^?1. We employ temporally shaped laser drives to compress Ta stepped foils over several to tens of nanoseconds. Lagrangian wave-profile analysis reveals a stress–density relationship which falls below the Hugoniot, above the hydrostat, and is consistent with ramp-compression experiments at lower strain rates. We also report on the peak elastic stress prior to plastic deformation as a function of strain rate for laser-driven ramp and shock-compression data spanning the 1–50?×?10⁷?s^?1 strain-rate range. When combined with previously published lower strain data (10¹–10⁷?s^?1), we observe a change in rate dependence, suggesting a transition from thermally activated to defect-limited (phonon drag) dislocation motion occurring at a strain rate of about 10⁵?s^?1.     

Test of Lorentz invariance through observation of the longitudinal development of ultrahigh-energy extensive air showers

An idea that Lorentz invariance can be violated was proposed by Coleman and Glashow to overcome the astrophysical problems of air showers of ultrahigh energies E>10²⁰ eV. This statement can be tested by analyzing experimental data on these showers. The longitudinal development of showers and the distribution of the depths of shower maxima were calculated in the model of quark-gluon strings with allowance made for the Landau-Pomeranchuk-Migdal effect and the interactions of ultrahigh-energy neutral pions. Comparison of the calculations with available experimental data provides a new bound |c _γ?c _π°| <0^?20 for the possible difference between the speeds of photons and neutral pions. This bound becomes |c _γ?c _π°|<10^?22 when one takes the upper limiting value for the observed depth of maximum.     

Variable range hopping mechanism in band-tail states of feldspars: A time-resolved IRSL study

Time-resolved infra-red stimulated luminescence (TR-IRSL) technique enables an understanding of the dynamics of trapped electrons after IR excitation in the band-tail states of feldspar. This work intends to study the underlying physical mechanism of IRSL production. TR-IRSL studies were carried out on four feldspar mineral specimens of variable chemical composition and structural state. Assuming the IR excited trapped electrons make random walks in the band-tail states and recombine by tunnelling dynamically, hopping time is derived from the OFF time data of TR-IRSL. This analysis indicates that the hopping time decreases with stimulation temperature. Using Einstein diffusion equation, hopping probability is computed and is shown to obey the equation describing variable range hopping mechanism of Mott kind. Mott's parameters (hopping length and hopping energy) are then derived. Hopping length decreases with stimulation temperature whereas hopping energy increases with temperature. The average hopping length and energy are in the range of 11–18 Å and 45–55 meV respectively and the diffusion constant is estimated to be in the range of 10^?10–10^?9 cm² s^?1 for all the feldspar samples.     

Radiative transition of hydrogen-like ions in quantum plasma

At fusion plasma electron temperature and number density regimes of 1?×?10³–1?×?10⁷?K and 1?×?10²⁸–1?×?10³¹/m³, respectively, the excited states and radiative transition of hydrogen-like ions in fusion plasmas are studied. The results show that quantum plasma model is more suitable to describe the fusion plasma than the Debye screening model. Relativistic correction to bound-state energies of the low-Z hydrogen-like ions is so small that it can be ignored. The transition probability decreases with plasma density, but the transition probabilities have the same order of magnitude in the same number density regime.     

Motion of an atom under the effect of femtosecond laser pulses: From chaos to spatial localization

The spatial localization of an atom in a field of periodic femtosecond laser pulses is considered. It has been shown that the atom can be localized with absolute accuracy in the nanometer range. The time interval during which the atom is situated in the laser field is only 10^?7–10^?8 of the total localization time interval.     

Thermal conductivity and Lorentz number of the “Golden” phase of the Sm1−x GdxS system with homogeneous variable valence of samarium

The thermal conductivity and electrical resistivity are measured in the temperature range 160–300 K for two compositions of the “golden” phase of the Sm_1?x Gd_xS system with x=0.14 and 0.3, in which a homogeneous variable valence of samarium ions is observed. It is found that, in this temperature range, the experimentally obtained Lorentz number L appearing in the electron component of thermal conductivity for these compositions exceeds the theoretical Sommerfeld value L ₀=2.45×10^?8 WΩ/K² typical of metals and highly degenerate semiconductors. It is also proved that the value of L increases with temperature in the interval 160–300 K starting from 160 K. A theoretical model capable of explaining the obtained experimental results is discussed.     

A radiotracer study of slow electron interaction with co on polycrystalline Mo

The interaction of slow (50–300 eV) electrons with CO chemisorbed on a polycrystalline Mo ribbon was investigated. A radiotracer was employed to monitor C concentration on the surface and desorbed ions were collected. From the time variation of the ion current, total electron induced desorption cross sections of 3.7 × 10^?17 to 1.6 × 10^?16 cm² were obtained. The desorption cross section for C containing species was found to be less than 1.4 × 10^?19 cm². In addition, the sticking coefficient for CO on Mo was found to be 0.13–0.16. These results are discussed in terms of the states of chemisorbed CO and the conclusions of other investigations of this systems.     

Ion-molecule collisions in gaseous111InCl and111InI systems

Using gaseous sources of¹¹¹InCl and¹¹¹InI with densities between 1.0·10¹⁷ cm^?3 and 4.4·10¹⁹ cm^?3 the perturbation of the 171.3–245.4 keVγ-γ cascade was measured as a function of time and density by the time-differential perturbed angular correlation (TDPAC) method. The anisotropy shows a strong dependence on the density. By means of an extended model based on a stochastic model of Bosch and Spehl collision cross sections for charge transfer and deorientation could be determined. The cross sections for charge transfer collisions were within the region from 2·10^?15 cm² to 26·10^?15 cm² and for deorientation collisions between 1·10^?15 cm² and 100·10^?15 cm².     

Comparative Study on Three Different Systems of Chemiluminescence Flow‐Injection Determination of Leucogen

Abstract

The effects of three systems on the chemiluminescence (CL) intensity have been studied in this paper, such as leucogen–potassium permanganate–rhodamine B, leucogen–cerium (IV)–rhodamine B, and leucogen–luminol–hydrogen peroxide (called system 1, system 2, and system 3, respectively). The mechanism of these reactions is also discussed. Surfactant (CTMAB) has a remarkably sensitive effect on these systems mentioned above. Therefore, three new flow injection chemiluminescence methods for the determination of leucogen have been established. For system 1, the linear range is 8.0×10^?8 to 4.0×10^?5 g mL^?1, with limits of detection 2×10^?8 g mL^?1; the relative standard deviation is 2.5% (n=11, Cs=4.0×10^?6 g mL^?1). For system 2, the linear range is 1.0×10^?8 to 5.0×10^?6 g mL^?1, with limits of detection 3×10^?9 g mL^?1; the relative standard deviation is 5.1% (n=11, Cs=1.0×10^?6 g mL^?1). For system 3, the linear range is 4.0×10^?8 to 2.0×10^?6 g mL^?1, with limits of detection 1×10^?8 g mL^?1; the relative standard deviation is 1.3% (n=11, Cs=1.0×10^?7 g mL^?1). Compared with the three methods above, system 3 is confirmed as the best method. This method has been applied to the determination of leucogen with satisfactory results.     

Investigation of excitation processes in a hollow-cathode discharge by time-resolved measurements in the vacuum u.v.

A spectrometer for the far u.v. range (λ = 30–300 nm) has been used, together with a sampling instrument (resolution 10^-9 s, time-intervals 10^?9to 10^?3s) for the measurement of afterglow. The measurements were confined to emission of the hollow cathode discharge. From the time constants of the afterglow, we conclude that the essential excitation processes for atoms in the hollow cathode are the following: direct electron excitation and three-body recombination.