射频辉光放电CH4等离子体一维流体动力学模拟

完整建立一个关于射频辉光放电CH₄等离子体的流体动力学模型.模型包括基于迁移-扩散近似的粒子平衡方程、电子能量平衡方程,共包含了20种粒子(环境气体粒子,激发态粒子,离子和电子)和49类化学反应(电子-中性环境粒子、离子-中性环境粒子、激发态粒子-激发态粒子(中性环境粒子)).结果表明,在强电场区域有较高的电子反应率系数;等离子体中除源气体CH₄外,H₂,C₂H₆,C₃H₈,C₂H₄和C₂H₂也有较高的密度含量;激发态粒子中,CH₃含量最高,密度约为10¹⁹m^-3;在较低放电压力时(如18 Pa),CH₅⁺在离子成分中密度含量最高,当放电压力较高时(如67Pa),C₂H₅⁺在离子成分中占主导地位;除C₂H₅⁺外,其它各离子和激发态粒子在极板上的粒子流量随功率的增大逐渐升高.     

Thermochemistry analyses for transformation of C6 glucose compound into C9, C12 and C15 alkanes using density functional theory

The hydrolysis of cellulose fraction of biomass yields C6 glucose which further can be transformed into long-chain hydrocarbons by C–C coupling. In this study, C6 glucose is transformed into three chain alkanes, namely, C9, C12 and C15 using C–C coupling reactions under the gas and aqueous phase milieus. The geometry optimisation and vibrational frequency calculations are carried out at well-known hybrid-GGA functional, B3LYP with the basis set of 6-31+g(d,p) under the density functional theory framework. The single point energetics are calculated at M05-2X/6-311+g(3df,2p) level of theory. All thermochemical properties are calculated over a wide range of temperature between 300 and 900 K at an interval of 100 K. The thermochemistry suggested that the aqueous phase behaviour is suitable for the hydrolysis of sugar into long-chain alkanes compared to gas-phase environment. The hydrodeoxygenation reactions under each reaction pathway are found as most favourable reactions in both phases; however, aqueous phase dominates over gas phase in all discussed thermodynamic parameters.     

Semiclassical analysis of α-transfer reactions

Semiclassical concepts are used to gain insight into α-transfer reactions. These reactions, interpreted as one-step direct reactions on the basis of DWBA analyses, are treated in analogy with single nucleon transfer reactions for which it is known that semiclassical methods are successful. In this case however the probability of transfer appears to be greatest at a distance of closest approach which is larger than the grazing distance by the order of the α-particle radius. This increase in the effective “grazing” distance is interpreted as a manifestation of the α-particle size at the time of transfer. Angular distributions are calculated semiclassically for the reactions ²⁰⁸Pb(¹⁶O, ¹²C)²¹²Po at 93 MeV and ⁴⁰Ca(¹²C, ⁸Be)⁴⁴Ti at 45 MeV lab energy. They are seen to give a reasonable fit to experiment. Partial wave amplitudes for transfer are also studied.     

Investigation of 91Zr by high resolution (d,p), (p,p′) and (p,d) reactions

Energy spectra and angular distributions of light particles (Z = 3–8) produced in the reactions ¹³C+^{58, 60, 64}Ni have been measured at 105 MeV. Coincidence events between light outgoing particles Li, Be, B and α, p have been observed for the first time in the ¹³C+⁵⁸Ni and ¹³C+⁶⁴Ni reactions. The results show that at least part of the ‘deep-inelastic’ events are due to many-particle reactions.     

天体演化过程中CNO核子辐射俘获反应

C和N核的质子辐射俘获反应对恒星平稳H燃烧阶段的能量产生和元素核合成起重要作用, C, N和O 核的中子辐射俘获是原初核合成和AGB星核合成的关键反应, 精确测定它们天体物理反应率有重要意义。 除13N(p, γ)14O和16N(n, γ)17N等不稳定核的核子辐射俘获反应外, 国际上已完成了其中若干反应的直接测量工作。 但12C(p, γ)13N, 13C(p, γ)14N和15N(p, γ)16O等CNO循环关键反应的实验测量还没有达到天体物理感兴趣的能区。 13C(n, γ)14C,15N(n, γ)16N和18O(n, γ)19O等中子辐射俘获反应测量的能量跨度较大, 截面仍存在较大的不确定性。 介绍了这些反应的研究进展, 并讨论了间接测量这些反应的方法和可行性。 The proton radiative capture reactions of C and N nuclei are important for the energy production and nucleosynthesis in the CNO cycle, and the neutron radiative capture reactions of C, N and O nuclei are key reactions for the inhomogeneous Big Bang nucleosynthesis as well as for the neutron induced CNO cycle in AGB stars. So far, most of these reactions have been measured except some reactions of the unstable nuclei, such as 13N(p, γ)14O and 16N(n, γ)17N. While the direct measured reactions, such as the  12C(p, γ)13N, 13C(p, γ)14N and 15N(p, γ)16O key reactions in CNO cycle, have not reached down to the stellar energies. In addition, the large uncertainties still exist in the measured neutron capture reactions such as 13C(n, γ)14C,15N(n, γ)16N and 18O(n, γ)19O. Thus it is significant to determine their astrophysical reaction rates via the indirect measurements. In this paper, the research status and feasibility of the indirect measurements for these reactions are discussed.     

Ultrasound promoted asymmetric transfer hydrogenation of ketones using Ru(II)arene/amino alcohol catalyst system

Asymmetric transfer hydrogenation of ketones using Ru(II)arene/amino alcohol catalyst system proceeds with significant rate enhancement by ultrasound promotion. Comparison of the silent reactions carried out at 25 degrees C with reactions under sonochemical activation at 25 degrees C clearly showed enhancement in catalytic activity by 5-10 times without significantly affecting the enantioselectivity.     

Transfer reactions induced by 17, 18O on 12, 13C at c.m. energies between 12.6 TO 14.0 MeV

Angular distributions for one-neutron and many-nucleon transfer reactions were measured in the systems ^{17, 18}O and ^{12, 13}C at c.m. energies between 12.6 to 14.0 MeV. All the cross sections were analyzed in terms of the full-recoil finite-range DWBA model. For multi-nucleon transfer processes an inert cluster transfer was assumed. The sensitivity of DWBA calculations to various parameter sets is discussed, and the effect of the no-recoil approximation on the phase and magnitude of the transfer amplitude is studied. For one-neutron transfer reactions the forward part of the angular distributions was reproduced reasonably well by the DWBA model, yielding satisfactory spectroscopic information. The rise of the cross section at the backward angles was not reproduced by the DWBA model. Possible contributions of cluster-exchange and compound-nucleus reactions are discussed. For multi-nucleon transfer reactions poorer fits were obtained, particularly in the ¹⁸O+¹²C system.     

Isospin mixing in 12C

We observe a yield to the 1⁺T = 1 level in ¹²C at 15.11 MeV in the isospin forbidden ¹²C(d, d') and ¹⁰B(α, d) reactions at about 1 % of the yield to the 1⁺T = 0 level at 12.71 MeV. Observed yields to the T = 12⁺ level at 16.11 MeV in both reactions at about half the yield to the 15.11 MeV level preclude attributing this observed isospin violation entirely to final state mixing. From the ratios of the spectroscopic factors for the 12.71 and 15.11 MeV levels in ¹²C and the ground state of ¹²B from the ¹³C(d, t) and ¹³C(d, ³He) reactions, we find a charge dependent matrix element between the 1⁺ states in ¹²C of 179 ± 75 keV.     

Evidence for a Soft Nuclear Equation-of-State from Kaon Production in Heavy-Ion Collisions

The production of pions and kaons has been measured in 197Au+197Au collisions at beam energies from 0.6 to 1.5A GeV with the kaon spectrometer at SIS/GSI. The K+ meson multiplicity per nucleon is enhanced in Au+Au collisions by factors up to 6 relative to C+C reactions, whereas the corresponding pion ratio is reduced. The ratio of the K+ meson excitation functions for Au+Au and C+C collisions increases with decreasing beam energy. This behavior is expected for a soft nuclear equation-of-state.     

Surfactant‐assisted specific‐acid catalysis of Diels–Alder reactions in aqueous media

Surfactant‐assisted specific‐acid catalysis (SASAC) for Diels–Alder reactions of dienophiles 1 and 4 with cyclopentadiene 2 in aqueous media at 32 °C was studied. This study showed that acidified anionic surfactants (pH 2) such as sodium dodecyl sulfate (SDS) and linear alkylbenzene sulfonic acid (LAS) accelerate Diels—Alder reactions. Conversely, under similar reaction conditions (pH 2) these reactions are inhibited by (acidified) cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), dodecyldimethylammonium bromide (DDAB), and dodecylmethylammonium bromide (DMAB). A modest rate acceleration resulting from the surfactant hydrogen‐bonding capacity is also recorded for the Diels–Alder reaction of naphthoquinones ( 6 ) with cyclopentadiene ( 2 ) in aqueous media at 32 °C. Copyright © 2007 John Wiley & Sons, Ltd.     

GAP和GAP/B的红外光谱和热分析研究

采用傅里叶红外光谱测试(FTIR)、热重法(TG)和微商热重法(DTG)研究了GAP和GAP处理硼的样品(GAP/B)在空气和氮气两种环境中的热分解。结果表明：GAP在约170 ℃开始发生叠氮基消除反应,250 ℃左右结束,GAP骨架的解聚反应延后了40 ℃左右;硼(B)改变了GAP的热分解过程,GAP/B在55～70 ℃开始分解,明显提前于GAP本身,而且,叠氮基的消除反应与GAP骨架的解聚反应几乎同时发生。基于Kissinger热分析数据处理方法,对GAP和GAP/B两种体系在叠氮基消除阶段的热分解动力学进行了研究,结果发现在空气环境中,两种体系的活化能E的数值均较低,较易于发生反应,这是由于GAP与空气中的氧发生有氧热解所致。     

Interfering transfer processes in heavy-ion reactions

Heavy-ion reactions in which two different transfer processes may interfere are analyzed. Angular distributions of the reactions ¹⁴C(¹⁶O, ¹⁷O)¹³C and ¹⁴C(¹⁶O, ¹⁸O)¹²C were measured at incident energies of 20, 25 and 30 MeV. The strong oscillations observed at the Coulomb barrier together with a backward rise at higher energies are taken as evidence for the superposition of two competing transfer reactions. DWBA calculations for the two single transfer processes were performed using the fixed-range approximation, and the two transition amplitudes were summed coherently. The experimental angular distributions are well reproduced. The DWBA also explains the disappearance of the interference structures for higher transferred angular momenta l. Data on the reaction ¹¹B(¹⁶O, ¹⁵N)¹²C measured earlier are included in the analysis in order to show the systematic dependence on l-values.     

Kinetic measurements by variable-temperature photoelectron spectroscopy. The kinetic rate of the bicyclopentadiene to cyclopentadiene reaction in the medium-vacuum region

Using an appropriate reactor and variable-temperature photoelectron spectroscopy (VTPES), the kinetic rate-constant for the duration of bicyclopentadiene to cyclopentadiene is determined as approximately 1.9 s^?1 at 328°C and 0.1 torr. The study constitutes the first application of photoelectron spectroscopy to the quantitative investigation of chemical reactions. The technique might prove useful for the study of thermal decomposition reactions in the medium-vacuum region.     

A study of cylindrically symmetric solutions in $$f(R, \phi,X)$$ theory of gravity

The European Physical Journal C - Much theoretical effort and automatization are required to confront new physics models with experimental data for many types of particle reactions at future...     

First study of the (14C, 12C) reaction: Selectivity of the reaction and the energy levels of 28Mg and 30Si

The first measurements are reported for (¹⁴C, ¹²C) two-neutron stripping reactions. Energy spectra up to an excitation energy of 12 MeV have been measured at 69 MeV for the ²⁶Mg(¹⁴C, ¹²C) and ²⁸Si(¹⁴C, ¹²C) reactions. A strong selectivity of this reaction is observed. Using this selectivity, the comparison of the spectra suggests J^π assignments for several ³⁰Si and ²⁸Mg states. The results from the other two-neutron stripping reactions, (t, p) and (¹⁸O, ¹⁶O) are compared with those of the (¹⁴C, ¹²C) reaction.     

Limitation to complete fusion in the reactions 12,13C+48Ti and 30Si+30Si

Excitation functions of the reactions ^{12, 13}C+⁴⁸Ti and ³⁰Si+³⁰Si were measured by in-beam γ-ray spectrometry in the energy ranges 20–60 MeV for the ^{12, 13}C induced reactions and 55–126 MeV for the ³⁰Si+³⁰Si reaction. Light-particle angular distributions were measured at 46 MeV and 47.5 MeV for the ¹³C and ¹²C induced reactions. Measurements of elastic scattering angular distribution and particle-γ coincidences were carried out for the system ¹³C+⁴⁸Ti at 46 MeV. The limitation to complete fusion detected for the system ³⁰Si+³⁰Si appears to be related to entrance channel effects and is well reproduced by a barrier penetration calculation using the KNS potential. The angular distribution measurements carried out for the ¹²C+⁴⁸Ti and ¹³C+⁴⁸Ti systems allowed to identify an incomplete fusion mechanism with emission of direct α-particles before the formation of a fully equilibrated system.     

Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO2 radical and the following β‐scission reactions

Unsaturated fatty acid methyl esters are ubiquitous in biodiesel fuels. The C = C double bond greatly affects the combustion characteristics of biodiesel, especially its ignition behavior at low temperatures. In this work, we report detailed theoretical study on the mechanism and kinetics of the hydrogen abstraction reactions of linear unsaturated C6 methyl esters with hydroperoxy radical (HO₂), which play a critical role in the low‐temperature combustion of biodiesel. Reaction profiles are obtained via intrinsic reaction coordinate (IRC) analysis including the formation of reactant complexes and product complexes at the entrance and exit channels, respectively. The potential energy surfaces are explored at the CBS‐QB3 level. The following β‐scission reactions of the forming radicals are also investigated at the same level of theory. The high‐pressure limit rate constants for all the reactions in the temperature range from 500 to 2000 K are calculated via conventional transition‐state theory with quantum tunneling effect and fitted to the modified Arrhenius expression.     

Proton transfer induced by 13C at 30 MeV/u

Proton stripping (¹³C, ¹²B) and pick-up reactions (¹³C, ¹⁴N) on targets of ¹²C, ²⁷Al, ⁵⁸Ni and ⁹⁰Zr have been measured at 30 MeV/n. At these high incident energies new features appear in the population of final states due to the high relative velocities: (i) strong favouring of large l-values; (ii) strong selectivity in the population of spin-orbit partners, (iii) population of states and continua at high excitation energies. A DWBA analysis gives satisfactory agreement for the relative and absolute strength of the transitions. The properties of high energy induced transfer reactions are reviewed in their qualitative and quantitative aspects, i.e. the dependence on bound state and scattering parameters, incident energy. The population of unbound states and their relation to quasi-free reactions and break-up reactions is discussed.     

环戊二烯与二氢呋喃类化合物Diels-Alder反应的理论研究

采用量子化学密度泛函理论(DFT)在B3LYP/6-311++G **水平上对环戊二烯与2(5H)-呋喃酮、丁烯二酸酐和2,5-二氢呋喃的Diels-Alder反应机理进行了理论研究,并且考虑了溶剂化效应和取代基效应对反应机理及能垒的影响。结果表明,本文所涉及的环戊二烯与二氢呋喃类化合物的Diels-Alder加成反应是以协同方式进行的;羰基取代基的吸电子作用是造成产物中C(1)-C(2)、C(3)-C(4)键键长增加的主要原因;反应所涉及到的FMO相互作用主要是环戊二烯的HOMO与二氢呋喃类化合物的LUMO之间的相互作用,羰基对反应活化能的影响主要是通过降低呋喃类化合物的LUMO能级,减小与环戊二烯的HOMO的能级差异,从而有利于反应进行的;反应2的活化能垒最低,从动力学的角度考虑在室温下可以进行。     

环戊二烯与二氢呋喃类化合物Diels-Alder反应的理论研究

采用量子化学密度泛函理论(DFT)在B3LYP/6-311++G **水平上对环戊二烯与2(5H)-呋喃酮、丁烯二酸酐和2,5-二氢呋喃的Diels-Alder反应机理进行了理论研究,并且考虑了溶剂化效应和取代基效应对反应机理及能垒的影响。结果表明,本文所涉及的环戊二烯与二氢呋喃类化合物的Diels-Alder加成反应是以协同方式进行的;羰基取代基的吸电子作用是造成产物中C(1)-C(2)、C(3)-C(4)键键长增加的主要原因;反应所涉及到的FMO相互作用主要是环戊二烯的HOMO与二氢呋喃类化合物的LUMO之间的相互作用,羰基对反应活化能的影响主要是通过降低呋喃类化合物的LUMO能级,减小与环戊二烯的HOMO的能级差异,从而有利于反应进行的;反应2的活化能垒最低,从动力学的角度考虑在室温下可以进行。