Radial breathing-like mode of wide carbon nanoribbon

The radial breathing-like mode (RBLM), an interesting Raman mode, of the carbon nanoribbons (CNRs) with different widths have been calculated by the empirical Brenner potential. It is found that the RBLM frequencies of CNRs whose widths are larger than 25 Å follow a new 1/w rule, which is different from the rule, obtained for the narrow CNRs [J. Zhou, J. Dong, Appl. Phys. Lett. 91 (2007) 173108]. A continuum rod model is proposed to explain the new 1/w rule, which is also different from the previous simple one-dimensional oscillator model, suitable only for the narrow CNRs. Based upon the CNR's RBLMs, we have proposed a practical experimental method to determine the widths of CNRs by their Raman spectra.     

Quantum non-demolition measurement of photon number using weak nonlinearities

We propose an alternative method for the quantum non-demolition measurement of photon numbers wherein weak cross-Kerr nonlinearities are to be used. The usual approach to quantum non-demolition measurements of quantum number involves encoding the photon number, through a cross-Kerr interaction, into a phase shift of a probe coherent state which is then detected through balanced homodyning. Weak nonlinearities produce small phase shifts which are difficult to detect and distinguish. In the method we propose, unbalanced homodyning acts as a displacement operator on the probe beam coherent state such that the cross-Kerr interaction encodes the photon number into the amplitude of a new coherent state. The value of the photon number can be determined by inefficient photon counting on the new coherent state. Our proposed method requires fewer resources than does the usual approach.     

Conduction switching in aluminum nitride thin films containing Al nanocrystals

Conduction switching, i.e., a sharp change in the conduction from a lower-conductance state to a higher-conductance state or vice versa in aluminum nitride thin films embedded with Al nanocrystals (nc–Al) has been observed in the ramped-voltage and ramped-current current–voltage (I–V) measurements and the time-domain current measurement as well. Each state is well defined and its I–V characteristic follows a power law. It is observed that the conductance decreases (or increases) with charging (or discharging) in the nc–Al. It is shown that the conduction switching is due to the charging and discharging in the nc–Al at certain strategic sites. With the connecting (or breaking) of some conductive tunneling paths formed by the uncharged nc–Al due to the discharging (or charging) in the nc–Al at the strategic sites, a conduction switching occurs.     

一维链状锌配位聚合物[Zn(Pyphen)(PZDC)(H2O)]的水热合成、结构与荧光性质

The title coordination polymer, [Zn(Pyphen)(PZDC)(H2O)] (1) (Pyphen=pyrazino [2,3-f][1,10]phen-anthroline and H2PZDC=pyrazine-2,3-dicarboxylic acid) has been obtained by using hydrothermal synthesis andcharacterized by elemental analysis, IR, TG, fluorescence spectrum and X-ray diffraction single-crystal structureanalysis. The crystal is of triclinic, space group P1 with a=0.681 8(14) nm, b=0.743 9(15) nm, c=1.759 8(35) nm,α=94.329(30)°,β=95.514(30)°,γ=97.043(3)°,V=0.878 2(3)nm3,Z=2,Mr=481.73,Dc=1.822 g·cm-2,μ=1.452 mm-1,F(000)=448, Rint=0.033 9, R=0.042 5, wR=0.090 7. In complex 1, PZDC ligands link the Zn(Ⅱ) ions to form 1Dchain structures, and further extended into a 3D supramolecular framework through π-π interactions andhydrogen bonding interactions. In addition, complex 1 exhibits strong photoluminescence at room temperature.     

Collapse of the magnetic ordering and structural anomalies in the U La S system: neutron diffraction and specific heat measurements

We report specific heat and neutron diffraction measurements of seven samples in the solid solution system U_xLa_1-xS. All samples have the simple fcc NaCl crystal structure. Both specific heat and neutron diffraction confirm the suggestion from the earlier magnetic measurements that the ferromagnetism disappears abruptly at 0.57. Near there is a doubling of the electronic contribution to the specific heat, as compared to the value of 23 mJ mol^-1K^-2 in pure US. Around the widths of the nuclear Bragg peaks show a considerable broadening, as well as anomalies in the mean lattice parameter, as compared to those expected from Vegard's law. A preliminary analysis suggests this broadening may be due to a loss of long range lattice order near . However, these changes are independent of temperature, so that further experiments are necessary before they can be associated with the changes in magnetic behavior at . Received 18 September 1998     

Scanning force microscopy of ion-irradiated organic single crystals of benzoyl glycine

Single crystals of the amino acid benzoyl glycine (hippuric acid) are irradiated normal to the as-grown surface by highly charged Bi ions with a kinetic energy of 2.38 GeV and a fluence of 1×10¹⁰ ions/cm². The projectiles create circular craters with a mean diameter of 40 (10) nm on the surface of the crystal as observed by scanning force microscopy (SFM). The mean depth amounts to 4 (1) nm, this value being considered as a lower limit due to the finite radius of curvature of the force cantilever tip. Thus, on the average, each single-ion projectile seems to eject about 10⁴ molecules. On the surface of non-irradiated crystals, SFM reveals terraces of a few monolayers in height. In water, it was possible to visualize the lattice periodicity. Terraces were also observed on the irradiated crystal surface in the presence of the craters, indicating that the crystal is still intact at the given dose. Received: 25 May 2000 / Accepted: 26 May 2000 / Published online: 13 July 2000     

Ab initio density functional theory investigation of Li-intercalated silicon carbide nanotube bundles

We present the results of ab initio density functional theory calculations on the energetic, and geometric and electronic structure of Li-intercalated (6,6) silicon carbide nanotube (SiCNT) bundles. Our results show that intercalation of lithium leads to the significant changes in the geometrical structure. The most prominent effect of Li intercalation on the electronic band structure is a shift of the Fermi energy which occurs as a result of charge transfer from lithium to the SiCNTs. All the Li-intercalated (6,6) SiCNT bundles are predicted to be metallic representing a substantial change in electronic properties relative to the undoped bundle, which is a wide band gap semiconductor. Both inside of the nanotube and the interstitial space are susceptible for intercalation. The present calculations suggest that the SiCNT bundle is a promising candidate for the anode material in battery applications.     

Intense deuteron beam investigation by activation yield-ratio technique

In this work, the intense deuteron beam from a plasma focus device is investigated by the activation yield-ratio technique. It is shown that boron-carbide (B₄C) and boron-nitride (BN) are complimentary targets for high energy deuteron beam studies. For deuteron spectra of the form dNd/dE∝E−n, when deuteron spectra decrease relatively gradually (n<6) BN is a better choice, while for the case of very rapidly decreasing deuteron spectra (n>6), B₄C is more suitable.     

Thermal lens effects in an Er<Superscript>3+</Superscript>:YAG laser with crystalline fiber geometry

A resonantly diode-pumped high-power continuous-wave Er³⁺:YAG laser with a crystalline fiber geometry based on total-internal-reflection pump guiding is reported. Up to 9.4 W of output power could be generated and a slope efficiency of 46.8% was achieved. Intrinsic efficiencies reached up to 48.8% and an optimum outcoupling of ∼20% was found. A strong thermal lens was observed and cavity stability and hysteresis effects were studied.     

Interference effects in 157 nm laser ablated cones in polycarbonate and application to spatial coherence measurement

Conical structures formed in 157 nm laser-ablated polycarbonate exhibit a well-defined fringe structure with a period of a few 100 nm surrounding the cone base. Experiments and modelling studies of the interference produced by these micro-conical mirrors are shown to provide a means of measuring the spatial coherence of the highly multi-mode 157 nm laser.