Phase-matched high-order harmonics by interaction of Ar atoms with high-repetition-rate low-energy femtosecond laser pulses

High-order harmonics are generated by coherent interaction of an intense laser and atoms or molecules[1]. With the development of the intense ultrashort pulse laser, the research of high-order harmonic generation has reached the water-window in spectral region[2] and subfemtosecond in time domain[3]. Especially, the generation and application of subfemtosecond pulse led the study of high-order harmonic generation into a completely new world[4, 5]. It has made the study of ultrafast science fro…     

Synthesis of carbon nitride nanotubes with the C(3)N(4) stoichiometry via a benzene-thermal process at low temperatures

In this communication, we first report the direct synthesis of high-quality carbon nitride nanotubes (CNNTs) with inner diameters of 50-100 nm and wall thicknesses of 20-50 nm with the C(3)N(4) stoichiometry on a high-yield of 40%via a simple benzene-thermal process involving the reaction of C(3)N(3)Cl(3) with NaN(3) in a Teflon-lined autoclave at 220 [degree]C without using any catalyst or template.     

Growth of BaWO4 fishbone-like nanostructures in w/o microemulsion

BaWO(4) fishbone-like nanostructures with fourfold structural symmetry have been successfully grown in w/o microemulsion. The BaWO(4) fishbone-like nanostructures have four rows of nanorods, epitaxially grown on the stem and perpendicular to the stem. The obtained samples are characterized by means of XRD, TEM, HRTEM, and SEM. It is found that the water content has a large influence on the size of the product and the molar ratio between cations and anions plays an important role in the morphology of the product. It is assumed that site-selective surfactant adsorption may be responsible for the formation of the BaWO(4) fishbone-like nanostructures.     

Development of one-dimensional nanostructures through the crystallization of amorphous colloids

In this paper we have demonstrated that the crystallization method of amorphous colloids is convenient and feasible in the large-scale production of one-dimensional (1D) nanostructures. For the crystals with highly anisotropic structures, such as orthorhombic, trigonal, and hexagonal crystals, the crystallization generally tends to occur along the (001) axis. The preparation of orthorhombic bismuth sulfide (Bi2S3) nanorods and trigonal selenium ( t-Se) nanowires by the crystallization route was used as typical examples to illustrate the process and mechanism of crystallization. The as-prepared products were characterized with transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, and selected area electron diffraction. Additionally, the detailed crystal growth processes involved in the crystallization of amorphous Bi2S3 colloid were investigated by studying the morphology and structure of intermediates. It demonstrates that the growth of the nanorods is through two key steps: (1) the formation of multiple activated sites on the surface of spherical Bi2S3 colloid and (2) the subsequent preferential growth along these sites.     

Octanuclear metallocyclic Ni4Fc4 compound: synthesis, crystal structure, and electrochemical sensing for Mg2+

New, neutral octanuclearmacrocyclic compound Ni(4)Fc(4) was achieved via self-assembly from Ni(BF(4))(2) and a ferrocene-containing bis-tridentate ligand. The compound exhibits a channeled structure with cavities inside and senses the Mg(2+) electrochemically in the solid state.     

On comparison of jump point detection for an exchange rate series

The main purpose of this paper is to investigate the detection of jump points of a discontinuous function in the presence of a noise by the wavelet approach. A computing algorithm of our method is proposed and then applied to the daily exchange rate of US Dollar against Deutsche Mark. All the points detected by our method reflect very strong economic and political impacts. Other statistical methods to detect jump points have also been applied to the same exchange rate data. Our proposed method has produced more convincing empirical results than others.     

Efficient White Light Emitting Using an Electron Blocker in Non-Doped Type Organic Electroluminescent Devices

Non-doped type white organic electroluminescent (EL) devices using vacuum-deposited organic thin films of blue-emitting 4,4-bis(2,2 diphenylvinyl)-1,1-biphenyl (DPVBi) and yellow-emitting ultrathin 5,6,11,12-tetraphenylnaphthacene (rubrene) to generate white emission were fabricated. The two emitting layers are separated by an electron blocking layer of N,N-bis-(1-naphthyl)-N,N-diphenyl-1,1-biph-enyl-4,4-diamine (NPB). The thickness of the blocking layer determines the spectrum of the devices. In a device with 5 nm electron blocker of NPB, the CIE coordinates were well within the white region for voltage raging from 3 V to 14 V. The device has a maximum luminance of 7400 cd/m²(at current density of 830 mA/cm²) and maximum power efficiency of 1.67 lm/W at 5 V.     

Dissociation mechanism of 2-propanol on a Si(111)-(7x7) surface studied by scanning tunneling microscopy

Adsorption of 2-propanol, (CH3)2CHOH, on a Si(111)-7x7 surface was studied by scanning tunneling microscopy. (CH3)2CHOH adsorbs equally on the faulted and unfaulted half unit cells by forming Si-OCH(CH3)2 and Si-H on an adatom and rest atom pair. Si-OCH(CH3)2 is consecutively increased in each half unit cell, and the adsorption is saturated when every half unit cell has three Si-OCH(CH3)2, which corresponds to 0.5 of the adatom coverage. The sticking probability for the dissociation of (CH3)2CHOH is independent of the adatom coverage from 0 to 0.4, but it depends on coverage at higher than 0.4. By counting the darkened adatoms, Si-OCH(CH3)2 on the center adatom (m) and that on the corner adatom (n), it was found the m/n ratio is ca. 4 for the first dissociation of (CH3)2CHOH in virgin half unit cell, but it becomes ca. 1.9 and 1.8 when two and three Si-OCH(CH3)2 are contained in a half unit cell. This result reveals that the dissociation probability of (CH3)2CHOH at the adatom-rest atom pair site is influenced by the nearest Si-OCH(CH3)2 in the half unit cell.     

Synthesis of silver nanotubes by electroless deposition in porous anodic aluminium oxide templates

An electroless deposition method has been employed for the synthesis of silver nanotubes using porous anodic aluminium oxide as templates, by which high-yield silver nanotubes with length over ten microns have been synthesized.     

Universal pion freeze-out in heavy-ion collisions

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.