A Computerized System for the Measurement of Nanomaterial Field Emission and Ionization

We have developed a computerized system for measuring field electron emission （FE） and field ionization （FI）, which has a three-electrode configuration with emitters biased up to 25 kV, and is programmed by the Labview software. The current-voltage curves of nano-tip tungsten and carbon nanotube （CNT） arrays were measured. The electron emission of CNTs proceeded with a turn-on field of 1.24 V/μm and a threshold field of 1.85 V/μm. Compared to the field emission, field ionization turned on at 3.5 V/μm. Raman spectroscopy and scanning electron microscopy （SEM） measurements showed degradation of the CNTs after FE/FI testing. The measurement of a W-tip revealed strong electron emission and instability behavior at a field strength higher than 7.0 V/μm.

Production of heavy neutron-rich nuclei with radioactive beams in multinucleon transfer reactions

The production mechanism of heavy neutronrich nuclei is investigated by using the multinucleon transfer reactions of ^(136;148)Xe+^(208)Pb and ^(238)U+^(208)Pb in the framework of a dinuclear system model. The evaporation residual cross sections of target-like fragments are studied with the reaction system ^(148)Xe+^(208)Pb at near barrier energies. The results show that the final isotopic production cross sections in the neutron-deficient side are very sensitive to incident energy while it is not sensitive in the neutron-rich side. Comparing the isotopic production cross sections for the reactions of ^(208)Pb bombarded with stable and radioactive projectiles, we find that neutron-rich radioactive beams can significantly increase the production cross sections of heavy neutron-rich nuclei.

Microstructure and mechanical properties of TiN/AlN multilayers deposited by filtered vacuum arc deposition

Nanometer TiN/AlN multilayers were prepared on silicon substrate by filtered vacuum arc deposition.The structures of the nanometer TiN/AlN multilayer were studied by using X-ray diffraction. The 12 nm TiN/AlN multiplayer is composed of cubic TiN structure and hexagonal wurzite AlN structure, but the 2 nm period multilayer is composed of face centered cubic structure TiN and AlN with strong (200) texture. The surface roughness, hardness and elastic modulus of multilayer are dependent on the period of multilayer. The hardness of the TiN/AlN multilayers is higher than that suggested by a simple rule of mixture. The peaking hardness of nanometer TiN/AlN multilayers at period of 2 nm is about 42 GPa, much higher than that of 12 nm. The wear resistance of the nanometer TiN/AlN multilayers was also studied.

First-Principles Band Calculations on Electronic Structures of Ag-Doped Rutile and Anatase TiO2

The electronic structures of Ag-doped rutile and anatase Ti02 are studied by first-principles band calculations based on density functional theory with the full-potential linearized-augmented-plane-wave method. New occupied bands are found between the band gaps of both Ag-doped rutile and anatase TiO2. The formation of these new bands can be explained mainly by their orbitals of Ag 4d states mixed with Ti 3d states and are supposed to contribute to their visible light absorption.

Experimental and computational study of visible light-induced photocatalytic ability of nitrogen ions-implanted TiO2 nanotubes

Nitrogen-doped TiO2 nanotubes(TNTs)were prepared by ion implantation and anodic oxidation.The prepared samples were applied in photocatalytic(PC)oxidation of methyl blue,rhodamine B,and bisphenol A under light irradiation.To explore the influence of doped ions on the band and electronic structure of TiO2,computer simulations were performed using the VASP code implementing spin-polarized density functional theory(DFT).Both substitutional and interstitial nitrogen atoms were considered.The experimental and computational results propose that the electronic structure of TiO2 was modified because of the emergence of impurity states in the band gap by introducing nitrogen into the lattice,leading to the absorption of visible light.The synergy effects of tubular structures and doped nitrogen ions were responsible for highly efficient and stable PC activities induced by visible and ultraviolet(UV)light.

Effects of energy deposition on mechanical properties of sodium borosilicate glass irradiated by three heavy ions: P, Kr, and Xe

Sodium borosilicate glasses are candidate materials for high-level radioactive waste vitrification;therefore, understanding the irradiation effects in model borosilicate glass is crucial. Effects of electronic energy deposition and nuclear energy deposition induced by the impact of heavy ions on the hardness and Young’s modulus of sodium borosilicate glass were investigated. The work concentrates on sodium borosilicate glasses, henceforth termed NBS1 (60.0% SiO2, 15.0% B2O3, and 25.0% Na2O in mol%). The NBS1 glasses were irradiated by P, Kr, and Xe ions with 0.3 MeV, 4 MeV, and 5 MeV, respectively. The hardness and Young’s modulus of ion-irradiated NBS1 glasses were measured by nanoindentation tests. The relationships between the evolution of the hardness, the change in the Young’s modulus of the NBS1 glasses, and the energy deposition were investigated. With the increase in the nuclear energy deposition, both the hardness and Young’s modulus of NBS1 glasses dropped exponentially and then saturated. Regardless of the ion species, the nuclear energy depositions required for the saturation of hardness and Young’s modulus were apparent at approximately 1.2 × 10^20 keV/cm^3 and 1.8 × 10^20 keV/cm^3, respectively. The dose dependency of the hardness and Young’s modulus of NBS1 glasses was consistent with previous studies by Peuget et al. Moreover, the electronic energy loss is less than 4 keV/nm, and the electronic energy deposition is less than 3.0 × 10^22 keV/cm^3 in this work. Therefore, the evolution of hardness and Young’s modulus could have been primarily induced by nuclear energy deposition.

Structural and Raman Analysis of Antimony-Implanted ZnMnO Films

Antimony ions were implanted into ZnMnO films grown on silicon （Si） by radio- frequency magnetron sputtering. The implanted samples were treated by rapid thermal annealing and investigated by X-ray photoelectron spectroscopy, X-ray diffraction and Raman scattering. In the wurtzite of ZnMnO, both manganese （Mn） and stibium （Sb） substituted the lattice position of zinc （Zn）. The ZnMnO films were characterized by Raman scattering at 522 cm-1, attributed to a local vibration of Mn. After implantation with Sb ions, two new peaks 681 cm^-1 and 823 cm^-1 were observed in the ZnMnO films, as a result of ion-induced damage to the lattice.

Quantum Dissipative Threshold and Its Effect on Decay of Metastable State

The coupling between system and reservoir is considered to be linear in the coordinates of the bath but nonlinear in the system's coordinate. A dissipative threshold is observed at finite temperatures due to nonlinear dissipation. The quantum decay rate of a metastable state including higher-order expanded terms of the coupling form function is proposed, which can be strongly decreased at finite temperatures when the quantum dissipative threshold is added to the saddle point of the potential.

Measurment of the energy spectrum of an electron beam extracted from an accelerator

The electron energy spectrum is one of the most important characteristics of an electron beam that is extracted from a linear accelerator. The most direct way to determine an electron spectrum would be to use a magnetic spectrometer and this method could also give results with high precision and effectiveness. In this article we describe our design of a new multi-layer absorption method, which is based on the depth-dose curves method that can be used in most irradiation accelerators, and adds the Monte Carlo simulation and iterative algorithm in order to reconstruct the electron energy spectrum. In this article the energy spectrum was measured using these two methods, and good results were acquired. These results could be crosschecked, which made the results more reliable.

Excitation and Ionization of Ethylene by Charged Projectiles

Using the time dependent local density approximation, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, the collision process between ethylene and fast charged projectiles is studied in the microscopic way. The impact of ionic motion on the ionization is explored to show the importance of treating electronic and ionic degrees of freedom simultaneously. The number of escaped electrons, ionization probabilities are obtained. Furthermore, it is found that the ionic extensions in different directions show the different patterns.

Fragmentation Cross Sections of ^12C on Different Targets at Beam Energies from 50 to 100 MeV/Nucleon

The fragmentation cross sections of reactions ^12C＋^2H, ^12C, ^14N, ^16O at beam energies from 50 to 100 MeV/nucleon are investigated using the isospin-dependent Boltzmann-Langevin equation model. It is found that fragment species increase approximately with the increasing target mass. The fragment species and some fragments production cross sections in reactions of ^12C＋^12C, ^14N, ^16O show an obvious variation at the beam energies from 50 to 80 MeV/nucleon. However the calculated fragment production cross sections do not change much when the incident energy increases from 80 to 100 MeV/nucleon.

A New Method to Measure the Divergence of X-Ray Beams from Capillaries

A new method to measure the divergence of x-ray beams propagated out from several capillaries is introduced, This new method is based on Bragg＇s law and is proven efficiently by the experimental measurement with collimators and straight polycapillaries.

Polymorphism and Flexibility of DNA in Alcohols

Molecular dynamics simulations are performed to investigate the polymorphism and flexibility of DNA in water,ethylene glycol(EG)and ethanol(EA)solutions.DNA in EG resembles the structure of DNA in water exhibiting B-DNA.In contrast,the DNA is an A-DNA state in the EA.We demonstrate that one important cause of these A$\leftrightarrow$B state changes is the competition between hydration and direct cation coupling to the phosphate groups on DNA backbones.To DNA structural polymorphism,it is caused by competition between hydration and cation coupling to the base pairs on grooves.Unlike flexible DNA in water and EA,DNA is immobilized around the canonical structure in EG solution,eliminating the potential biological effects of less common non-canonical DNA sub-states.

Liquid-to-glass transition of tetrahydrofuran and 2-methyltetrahydrofuran

Both tetrahydrofuran （THF） and 2-methyltetrahydrofuran （MTHF） are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consistent with experiment. Their glass transition temperatures are obtained： 115 K - 130 K for THF and 131 K - 142 K for MTHF. The calculated results from the dipolar orientational time correlation functions indicate that the ＂long time＂ behavior is often associated with a glass transition. From the radial and spatial distributions, we also find that the methyl has a direct impact on the structural symmetry of molecules, which leads to the differences of physical properties between THF and MTHF.

A theoretical study of fragmentation dynamics of water dimer by proton impact

To investigate the collision processes of proton with the water dimer(H_(2)O)_(2)at 50 e V,the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied.Six specific collision orientations with various impact parameters are considered.The reaction channels,the mass distribution and the fragmentation mass spectrum are explored.Among all launched samples,the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%,hinting that the probability of fragmentation is about 20%.The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions,the respective distance,the number of loss of electrons and the evolution of the electron density.The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments,the fragment with mass 36 has the highest relative abundance of 65%.The relative abundances of fragments with masses 1,35,and 34are 20%,13%,and 1.5%,respectively.For the total electron capture cross section,the present calculations agree with the available measurements and calculations over the energy range from 50 e V to 12 ke V.

Secondary Beam Fragments Produced by 200 and 400 MeV/u ^12C^6＋ Ions in Water

Based on the GEANT4 toolkit, we study the transportation of nucleons and nuclei in tissue-like media. The fragmentation of projectile nuclei and secondary interactions of produced nuclear fragments are considered. Livermore data is used to calculate electromagnetic interaction of primary and secondary charged particles. We validate the models using experimental data of 200 MeV/u and 400 MeV/u carbon ions, interacting with tissue equivalent materials of water. The model can well describe the depth-dose distributions in water and the doses measured for secondary fragments of certain charge and certain mass number. The secondary beam fragments produced by 200 MeV/u and 400 MeV/u ^12C^6＋ ions in water are investigated using the model. When the primary nuclei are in water, several neutron production mechanisms are involved. The light charged particles （p, d, t, ^3He and ^4He） and fast neutrons contribute to the dose tail behind the Bragg peak. The ^11C fragments which may be the most suitable nuclei for monitoring the energy deposition in carbon-ion therapy are also discussed.

Theoretical Investigation of the Exotic Structure of the Mirror Nuclei ^17Ne and ^17N

The exotic structures of the ground state of the mirror nuclei ^17Ne and ^17N are investigated by means of the asymptotic normalization coefficient （ANC） method to explore the role of the Coulomb interaction, The probebilities of a valence nucleon outside the binding-potential are P = 56.69±2.98/7.46% for ^17Ne and P = 45.51±2.32/5.81% for ^17N. The rms radii are （r^2）^1/2 = 5.06±0.11/0.30 fm and （r^2）^1/2=4.24±0.06/0.16 fm, respectively. The results obtained are nearly independent of the potential parameters. According to the halo occurrence conditions, it is suggested that ^17Ne is a two-proton halo and ^17N is a two-neutron skin. Moreover, two effects of the Coulomb interact-ion on the exotic structure are analysed. From the present results, the exotic structure of the nucleus in the proton-rich side is more obvious than that of its mirror nucleus because of the Coulomb interaction.

Advancements in heterojunction,cocatalyst,defect and morphology engineering of semiconductor oxide photocatalysts

Photocatalytic technology has emerged as a crucial avenue for harnessing solar energy,presenting itself as a viable solution to address the current energy crisis and environmental pollution.The past 50 years have witnessed significant progress and breakthroughs in scientific research on photocatalytic tech-nology.This paper provides a comprehensive review of the mechanism of photocatalytic technology and methods to improve the photocatalytic efficiency of semiconductor photocatalysts,such as TiO 2 and ZnO.In this paper,common modification methods are divided into four categories:heterojunction con-struction,cocatalysts,defects,and morphological engineering.The origin and development of photo-catalysts in each category are briefly summarized;moreover,the latest progress in each type of modification is discussed.S-scheme heterojunctions retain the high reduction and oxidation capacity of photogenerated electrons and holes by sacrificing half of the photogenerated carriers,showing excellent performance in photocatalysis and great application potential.The challenges associated with current modification schemes are presented.There is growing interest in quantitative and atomic-level modu-lation as attractive approaches to tackling these challenges.Regulating the electronic spin state and internal field is important for minimizing photogenerated carrier recombination in photocatalysis.This review will inspire researchers and promote the application of photocatalytic technology.

One-neutron stripping process in the^(209)Bi(^(6)Li,^(5)Li)^(210)Bi*reaction reaction

One-neutron stripping process between^(6)Li and^(209)Bi was studied at 28,30,and 34 MeV using the in-beamγ-ray spectroscopy method.Theγ-γcoincident analysis clearly identified twoγ-rays feeding the ground and long-lived isomeric states,which were employed to determine the cross section.The one-neutron stripping cross sections were similar to the cross sections of complete fusion in the^(6)Li+^(209)Bi system,but the one-neutron stripping cross sections decreased more gradually at the sub-barrier region.A coupled-reaction-channel calculation was performed to study the detailed reaction mechanism of the one-neutron stripping process in^(6)Li.The calculations indicated that the first excited state of 5 Li is critical in the actual one-neutron transfer mechanism,and the valence proton of 209Bi can be excited to the low-lying excited state in(^(6)Li,^(5)Li)reaction,unlike in the(d,p)reaction.

Efficient Quantum Cryptography Network without Entanglement and Quantum Memory

An efficient quantum cryptography network protocol is proposed with d-dimensional polarized photons, without resorting to entanglement and quantum memory. A server on the network, say Alice, provides the service for preparing and measuring single photons whose initial state are ｜0〉. The users code the information on the single photons with some unitary operations. To prevent the untrustworthy server Alice from eavesdropping the quantum lines, a nonorthogonal-coding technique is used in the process that the quantum signal is transmitted between the users. This protocol does not require the servers and the users to store the quantum states and almost all of the single photons can be used for carrying the information, which makes it more convenient for application than others with present technology. We also discuss the case with a faint laser pulse.