Application of synchrotron radiation to investigation of the mechanism of increase in the yield of alkali metal ions in electron-stimulated desorption

Core-level photoelectron spectroscopy with synchrotron radiation (hv = 140 eV) has been applied to study the variation in the Si⁺ charge state in silicon films deposited on the W(100) surface after thermal annealing of the substrate. The purpose of this study is to check the mechanism responsible for the sharp increase in the yield of Na⁺ ions in electron-stimulated desorption from a sodium layer adsorbed on the Si/W(100) surface after high-temperature annealing. The evolution of the W 4f _7/2 and Si 2p photoelectron spectra and the valence band photoemission spectra is investigated for two silicon coverages (1 and 3 ML) on the W(100) surface in the temperature range 300<T<2200 K. It is shown that annealing of 1 ML Si on the W(100) surface results in the formation of a W-Si covalent bond, which can weaken the Si-Na bond and lead to an increase in the equilibrium distance X ₀ and, hence, to an increase in the yield of Na⁺ ions in electron-stimulated desorption. The variation in the photoelectron spectra under annealing of 3 ML Si differs from that observed after annealing of 1 ML Si in the direction of charge transfer, thus correlating with the opposite effect of annealing of 3 ML Si/W on the Na⁺ yield in electron-stimulated desorption.     

Single-spin asymmetry of inclusive neutral-pion production in pp ↑ interactions at 70 GeV in the region −0.4 < x F < −0.1

For the kinematical region specified by the inequalities ?0.4 < x _F < ?0.1 and 0.9 < p _T < 2.5 GeV/c, the results are presented that were obtained by experimentally determining the single-spin asymmetry of inclusive neutral-pion production in the reaction p + p _↑ → π ⁰ + X at 70 GeV. According to these results, the asymmetry is close to zero in the region ?0.2 < x _F < ?0.1 and grows in magnitude with decreasing x _F, amounting to (?10.6 ± 3.2)% for ?0.4 <x _F < ?0.2.     

Nuclear levels in 228Th populated in the decay of 228Pa (II)

The electron-capture decay of ²²⁸Pa to levels in ²²⁸Th was studied using mass-separated sources and a γ-ray detection system consisting of five Compton-suppressed Ge detectors. A total of 87 levels were observed up to an excitation energy of 2 MeV which are connected by approximately 500 γ-ray transitions. The complete octupole quadruplet, three excited K ^π=0⁺ bands and two K ^π=2⁺ bands were identified below 1.4 MeV. The observed level structure is compared to calculations within the quasiparticle-phonon nuclear model. The surprisingly good agreement indicates that ²²⁸Th has less transitional character than hitherto assumed. Received: 30 March 1998     

Phase Logic Based on π Josephson Junctions

JETP Letters - The transition to Josephson digital circuits with the representation of information in the form of phase jumps of the superconducting order parameter on heterostructures promises a...     

Observation of Brownian relaxation of magnetic nanoparticles using HTS SQUID

We analyzed the sensitivity of a separationless immunoassay scheme using functionalized magnetic nanoparticles (MNPs) and a sensitive HTS SQUID magnetometer. The signal of a 100 μL sample at a concentration of 1 mg/mL and field of 7.5 nT was 20 mΦ₀. This makes it possible for the sensitivity to be within the range of 50 ng/mL at the required time of up to 100 s per a point in the frequency spectrum.     

Noncommutative deformations of quantum field theories,locality, and causality

We investigate noncommutative deformations of quantum field theories for different star products, particularly emphasizing the locality properties and the regularity of the deformed fields. Using functional analysis methods, we describe the basic structural features of the vacuum expectation values of star-modified products of fields and field commutators. As an alternative to microcausality, we introduce a notion of θ-locality, where θ is the noncommutativity parameter. We also analyze the conditions for the convergence and continuity of star products and define the function algebra that is most suitable for the Moyal and Wick-Voros products. This algebra corresponds to the concept of strict deformation quantization and is a useful tool for constructing quantum field theories on a noncommutative space-time.     

Study of Cross-Correlation between Information Matrixes of Observation of the URAGAN Hodoscope and Dst Index

Cross-correlation between observation matrixes of the URAGAN muon hodoscope and the Dst index was studied. Functions of total intensity and anomaly were introduced. The results of calculations of cross-correlations on 2D diagrams were considered. It was shown that time periods with increased geomagnetic activity were almost always preceded by time periods with increased values of the modulus of the Pearson correlation coefficient.

     

Size of the proton emission region inp-C,d-C, α-C and C-C interactions at 4.2 GeV/c per incident nucleon from two-proton correlations

Correlations between secondary protons with small relative momenta have been studied in interactions of various light nuclei with the carbon target at 4.2 GeV/c per incident nucleon with the aim to determine the radius of the proton emission region. This radius is found to decrease with increasing momentum and transverse momentum of the proton pair, but it does not show any dependence on the mass of the projectile nucleus.     

Description of radiative strength functions in deformed nuclei

Radiative strength functions ofE1- andM1-transitions from ground states of doubly even deformed nuclei to states near the neutron binding energyB _n are calculated within the quasiparticle-phonon nuclear model. The wave functions of excited states include one- and two-phonon components. The calculations were made with the Pauli principle being or not included in the two-phonon components of the wave functions. It is shown that the radiativeE1- andM1-strength functions as well as the widths of giant dipole resonances in deformed nuclei are slightly influenced by the two-phonon components of the wave functions and they can be calculated in the RPA. Thek _E1- andk _M1-values are calculated for some deformed nuclei of the rare-earth and actinide region. The calculated values ofk _E1 are 1.5–2 times larger and the values ofk _M1 are somewhat less than the average values obtained in [14] from the analysis of available experimental data.     

Breaking the space-time translation group in the dipole field model

The impossibility of constructing a translation-invariat physical space for the massless dipole field models in two and four dimensions follows from the Lebesgue integral theory. The method of proof may also be useful for studying space-time symmetries in other models with singular behavior in the infrared domain. To fix the Hilbert majorant structure associated with an indenfinite metric, we impose the condition that the majorant structure inherit the homogeneity properties from the metric. Translated from Teoreticheskaya i Matematicheskaya Fizika. Vol. 115. No. 2. pp. 163 176. May. 1998.