Quantum phase transition and entanglement in Li atom system

By use of the exact diagonalization method, the quantum phase transition and entanglement in a 6-Li atom system are studied. It is found that entanglement appears before the quantum phase transition and disappears after it in this exactly solvable quantum system. The present results show that the von Neumann entropy, as a measure of entanglement, may reveal the quantum phase transition in this model.     

A kinetic model for alternate oscillation of self-terminating and recombination lasers in strontium ions

A self-consistent model has been developed to simulate the kinetics of alternate oscillation of self-terminating and recombination lasers in univalent ions of strontium excited by the high-repetition-rate (HRR) pulsed discharge. Photoelectric pulse waveforms predicted by the model are in good agreement with the experimental measurement. The model also gives temporal behaviors of long-life particles, the population densities of upper and lower laser levels and the electron temperature (Te) in He-Sr discharge plasma. The emission process of the two laser alternate oscillations, the characteristic of the laser pulse width and the population inversion mechanics are also analyzed.     

Fabrication of fluorinated polyimide optical waveguides by micropen direct writing technology

A novel and cheap direct writing method based on the micropen has been developed to fabricate fluorinated polyimide stripe optical waveguides on Si/SiO₂ wafers. The overall design, starting material, micropen direct writing system and fabrication processes of the stripe optical waveguides are presented. The effects of the key direct writing parameters, such as the tip-to-substrate distance, extrusive gas pressure, writing speed and viscosity of the polyamic acid, on the dimension and morphology of the stripe optical waveguides are discussed in detail. After deposition by the micropen system and baking process, the fluorinated polyimide stripe optical waveguides with good morphology and surface quality can be fabricated using the optimal parameters. The propagation losses at the wavelength of 1.55 μm are in the range of 1.4-3.5 dB cm⁻¹ as characterized by different length combinations of the strip optical waveguides.     

A theoretical study of thiophenic compounds adsorption on cation-exchanged Y zeolites

A density functional theory (DFT) method has been applied to study the adsorption of thiophenic compounds such as thiophene (TP), benzothiophene (BT), dibenzothiophene (DBT) on cation-exchanged Cu(I)Y, Ni(II)Y, Ce(III)Y zeolites. All of calculations were carried out by the generalized gradient approximation (GGA) with the BLYP exchange-correlation functional and DNP basis set. The calculated results indicate that the stable adsorption configuration of TP molecule adsorbed on the Cu(I)Y is the η5 adsorption mode, whereas for BT and DBT, the η1S adsorption mode was found for the both molecules. Only the η1S adsorption mode can be obtained for the three thiophenic compounds adsorbed on the Ni(II)Y. The η5 adsorption mode can be ascribed to the adsorption of thiophene molecules on the Ce(III)Y, but the competition of different adsorption modes could possibly occur during the adsorption process of BT and DBT on the Ce(III)Y. Moreover, the selectivity of TP adsorbed on the adsorbents is in the order of Cu(I)Y > Ce(III)Y > Ni(II)Y, while for BT and DBT, the order is Cu(I)Y > Ni(II)Y > Ce(III)Y.     

Even factors with a bounded number of components in iterated line graphs

We consider even factors with a bounded number of components in the n-times iterated line graphs L ⁿ (G). We present a characterization of a simple graph G such that L ⁿ (G) has an even factor with at most k components, based on the existence of a certain type of subgraphs in G. Moreover, we use this result to give some upper bounds for the minimum number of components of even factors in L ⁿ (G) and also show that the minimum number of components of even factors in L ⁿ (G) is stable under the closure operation on a claw-free graph G, which extends some known results. Our results show that it seems to be NP-hard to determine the minimum number of components of even factors of iterated line graphs. We also propose some problems for further research.     

Temporal study of GRS 1915+105 with rms-flux relation: The importance of magnetic activities in the corona

The rms-flux relations for some observations of GRS 1915+105 are studied. The rms-flux relations of the light curves in only one state, state C or state A, can be described by the simple non-linear model provided Zhang; we thus interpret that such a linear relation reflects the relative importance of magnetic instability for X-ray emission in the corona of the system, compared to the thermal viscous instability for the X-ray emission in the accretion disk. The rms-flux relations for state B are very scattered, possibly because of the dominance of thermal viscous instability for the X-ray emission in the accretion disk. The complex rms-flux relations for the observations of transitions between two or three states are caused by the combination of the different rms-flux relations of these states. The underlying physical processes are the combination of magnetic topology in the corona and thermal viscous instability in the accretion disk.

     

Fast and sensitive trace metal analysis in aqueous solutions by laser-induced breakdown spectroscopy using wood slice substrates

To perform fast and sensitive trace metal analysis in aqueous solutions by laser-induced breakdown spectroscopy (LIBS) based on only one single-pulse laser system, a wood slice has been used as a liquid absorber to transform liquid sample analysis to solid sample analysis using LIBS. High detection sensitivity and good reproducibility can be achieved with this approach. Calibration curves for five metal elements, Cr, Mn, Cu, Cd, and Pb under trace concentrations, have been obtained, and the limits of their detection were determined to be in the range of 0.029–0.59 mg L^− 1, 2–3 orders better than those obtained by directly analyzing liquid samples where the laser was focused on a liquid surface. The wood slice was very easy to handle and thus, the whole analysis process took only 4–5 min for each sample. This approach provides a more practical approach for fast and sensitive metal element analysis in aqueous solutions using LIBS, which is especially useful for monitoring toxic heavy metals in water.     

Pair Excitations in Even-Even Nuclei

A charge exchange term is added to the n-p effective interaction in treating eveneven nuclei with shape coexistence. The energy spectra and some of the E2 transition rates are calculated for ^112,114Cd, ^114,116Sn and ^118,120Te nuclei. The inclusion of this new term helps to improve an agreement with experimental data.     

Charge Exchange Component of n-p Interactions

An extra term of n-p effective interaction containing charge exchange component is proposed and applied to treating odd-mass nuclei with shape coexistence. The energy spectra and some E2 transition branching ratios are calculated for odd-A nuclei ^113~125Sb,^115~127I. With the inclusion of new term, an overall agreement with experiment is much improved.