100keV质子与低高能质子在绝缘微孔中输运特性的对比分析

为研究中能区带电粒子在绝缘微孔中传输的物理图像,利用MATLAB程序和蒙特卡罗方法建立理论模型,得到入射能量为10 keV,100 keV和1 MeV的质子,以-1?倾斜角入射到微孔后,出射粒子角分布、沉积电荷斑分布,以及粒子在微孔内的运动轨迹等传输特性.研究结果表明,在10 keV的低能区,微孔内壁沉积电荷的导向效应是主要的传输机制.在1 MeV的高能区,进入表面以下多次随机非弹性碰撞是主要的输运机制.在100 keV的中能区,无电荷斑时,主要是以进入表面以下的随机二体碰撞为传输机制;在电荷斑累积过程中,增强的库仑排斥力逐渐抑制入射质子在微孔内壁表面发生电子俘获;当达到充放电平衡后,主要传输机制为电荷斑辅助的近表面镜面散射行为.这一特性加深了对中能区质子在微孔中输运行为的认识,有助于对百keV质子微束的控制和应用.     

Antiproton-hydrogen scattering at low-eV energies

In the scattering of negative particles other than the electron by atoms at lab-frame energies around 10 eV, an elastic process termed “brickwall scattering” might lead to a high probability for scattering angles around 180°. For an antiproton slowing in hydrogen, this backward scattering would result in the loss of nearly all of its energy in a single collision, since it and a hydrogen atom have nearly the same mass. Such energy loss would have a significant effect on the energy distribution of antiprotons at energies where capture by the protons of hydrogen is possible and might, thereby, affect the capture rate and the distribution of capture states. In the semiclassical treatment of the problem with an adiabatic potential energy, brickwall scattering is indeed present, and with a substantial cross section. However, this model appears to underestimate inelastic processes. Based on calculations for negative muons on hydrogen atoms, these processes appear to occur for about the same impact parameters as brickwall scattering and thus substantially reduce its effect.     

Attosecond physics with neutrons and electrons: Ultrafast entanglement and decoherence phenomena involving protons in condensed matter and molecules

Nuclei and electrons in condensed matter and/or molecules are usually entangled, due to the prevailing electromagnetic interactions. Usually, the “environment” of a microscopic scattering system (e.g., a proton) causes an ultrafast decoherence, thus making atomic and/or nuclear entanglement effects not directly accessible to experiments. However, neutron Compton scattering (NCS) and electron Compton scattering represent ultrafast techniques operating in the sub-femtosecond timescale, thus opening a way for investigation of such dehoherence and short-lived entanglement phenomena of atoms in molecules and condensed matter. The experimental context of NCS and a new striking scattering effect from protons (H-atoms) in several condensed systems and molecules are described. In short, one observes an “anomalous” decrease of scattering intensity from protons, which seem to become partially “invisible” to the neutrons. The experiments apply large energy (several electronvolts) and momentum (10–200 Å^?1 transfers, and the collisional (or scattering) time between the neutron and a struck proton is only 100–1000 attoseconds long. Similar results are also obtained with electron-atom Compton scattering at large momentum transfers. As an example, we present new NCS experimental results from a single crystal, which also provide new physical insights into the attosecond quantum dynamics of protons in molecules and condensed matter. Theoretical discussions and models are presented which show that the effect under consideration is caused by the non-unitary time evolution (due to decoherence) of open quantum systems during the ultrashort, but finite, time-window of the neutron-proton scattering process. The conceptual connection with the well known Quantum Zeno Effect is pointed out. The experimental results, together with their qualitative interpretation “from first principles,” show that epithermal neutrons being available at spallation sources, and electron spectrometers providing large momentum transfers, may represent novel tools for investigation of thus far unknown physical and chemical attosecond phenomena.     

Evidence for strange-quark contributions to the nucleon's form factors at Q2=0.108 (GeV/c)2

We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of Q(2)=0.108 (GeV/c)(2) and at a forward electron scattering angle of 30 degrees p)=[-1.36+/-0.29(stat)+/-0.13(syst)]x10(-6). The expectation from the standard model assuming no strangeness contribution to the vector current is A(0)=(-2.06+/-0.14)x10(-6). We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher Q2. We have extracted the strangeness contribution to the electromagnetic form factors from our data to be G(s)(E)+0.106G(s)(M)=0.071+/-0.036 at Q(2)=0.108 (GeV/c)(2). We again find the value for G(s)(E)+0.106G(s)(M) to be positive, this time at an improved significance level of two sigma.     

含Cr (Ⅲ)溶液中配位水质子的1H NMR研究

本文用¹H NMR对水合Cr(Ⅲ)络离子中配位水和质子交换速率进行研究。在溶液pH为0~3.17范围测得质子的平均寿命约为10^-5S。在pH为0~0.76范围质子交换反应动力学为一、二级混合过程。pH为0.76~1.6范围表现为一级过程。在Cr(Ⅲ)-H₂O-Gly系统中,实验得出配位水质子的活动性减小。     

Comparison of electron and neutron compton scattering from entangled protons in a solid polymer

We present, for the first time, a direct comparison between electron (ECS) and neutron (NCS) Compton scattering results from protons of a solid polymer. The momentum distributions of hydrogen obtained from ECS and NCS are in excellent agreement. In both experiments, a strong "anomalous" shortfall in the scattering intensity of protons [first detected in liquid water with NCS [Phys. Rev. Lett. 79, 2839 (1997)]]] is found ranging from about 20% up to 50%, depending on the momentum transfer applied. The characteristic times of electron- and neutron-proton collisions lie in the subfemtosecond range. The presented ECS and NCS results provide further direct evidence for this striking effect, which has been ascribed to attosecond quantum entanglement of the protons.     

Spin-dependent effects in inelastic scattering

The differential cross sections for the inelastic scattering of 10 MeV, 19.6 MeV, 30.4 MeV, 40 MeV and 49.35 MeV protons to the 2⁺ state (1.409 MeV) in ⁵⁴Fe and of 19.6 MeV protons to the 2⁺ state (0.846 MeV) in ⁵⁶Fe are analyzed in conjunction with the available data on the asymmetries and spin-flip probability amplitudes. The scattering amplitudes for both one step (valence plus core polarization) and two step (intermediate resonance) processes are evaluated using an antisymmetrized distorted wave approximation. Collective model representations for both the one step (core polarization) and two step (intermediate resonance) processes are used, and included are the effects of deforming the full Thomas spin-orbit potentials. The one step processes are fixed by the analyses of the scattering of 30.4, 40 and 49.35 MeV protons, with the core polarization contributions being constrained by the B(E2) values for the γ-ray deexcitation of the 2⁺ states. The analyses of the 19.6 MeV data demonstrates the need for an extra (two step) contribution to the reaction process and are consistent with the virtual formation of an L = 3 giant resonance. The 10 MeV data most certainly demonstrate compound nucleus effects but could also have some strength due to the virtual formation of an intermediate L = 2 giant resonance. The resonance parameters are consistent with recent information concerning the mass variation of giant resonances.     

Nonrelativistic description of nucleon-nucleus scattering

Within the three-dimensional semiclassical approximation, an analytic expression is obtained for the amplitude of proton-nucleus scattering at intermediate energies of incident protons. The method for deriving this amplitude is based on the use of the high-energy approximation with distorted waves. In view of the short-range character of proton-nucleon interaction, the process of proton-nucleus scattering is represented as a series of single scattering events occurring on each individual nucleon. With the aid of the proposed mathematical formalism, a recursion relation is derived that makes it possible to express the nuclear form factor obtained within the distorted-wave method in terms of the sum of an infinite Born series. Parameters that characterize the distributions of protons and neutrons in the spherical nuclei ⁴⁰Ca, ⁴⁸Ca, ⁹⁰Zr, and ²⁰⁸Pb and which include the width of the surface layer of nucleons and the root-meansquare radii of the proton-, neutron-, and nucleon-density distributions are determined from an analysis of the measured cross sections for the elastic scattering of 1-GeV protons, a modified Fermi function being employed for the nucleon-density distribution.     

20 keV质子在聚碳酸酯微孔膜中传输的动态演化过程

测量了20 ke V质子穿过倾斜角为+1?的聚碳酸酯微孔膜后,出射粒子的位置分布、相对穿透率以及电荷纯度随时间的演化.实验发现,能量电荷比E/q≈10~1k V的质子穿过绝缘纳米微孔的物理机理与E/q≈10~0k V和E/q≈10~2k V区域离子有显著不同.对于E/q≈10~1k V的质子穿过绝缘纳米微孔,存在一段相当长的导向建立之前(导向前)的过程,在该时期内出射质子及氢原子的特性和导向建立后的特性有很大差异.在导向前的演化过程中,我们可以观察到出射质子的峰位逐渐向孔轴向附近转移;出射氢原子由束流方向的尖峰以及孔轴向的主峰构成,峰位角保持基本不变且尖峰逐渐消失.这一过程的主要机理为微孔内表面以下的多次随机二体碰撞和近表面镜面反射两种传输方式逐步向电荷斑约束下的"导向效应"过渡的过程.对E/q≈10~1k V区间离子"导向前过程"的完整观测,使得对低能向中能过渡区间离子穿过绝缘微孔膜物理机制和图像有更深入和完整的认识,有助于约10 ke V离子微束的精确控制和应用.     

On the elastic scattering of proton on deuteron at an energy of 8·2 GeV

The elastic scattering of a proton on a deuteron at an energy of 8·2 GeV was studied by the method of nuclear photoemulsions. A stack, composed of 20 emulsions of the type NIKFI-R diluted with heavy water, was irradiated with an internal beam of protons on the synchrophasotron in the Joint Institute of Nuclear Research in Dubna. The beam was perpendicular to the plane of the emulsion and had an intensity of (3·36±0·10)×10⁵ protons/cm².Altogether 114 events of elastic scattering (p-d) and 62 events of elastic scattering (p-p) were found. The differential cross-section of elastic scattering (p-d) was determined in a range of scattering angles of 1–3° to 10° in CMS. The total cross-section of elastic scattering (p-d) in this range of angles was found to be _el =(9·74±1·10) mb.The effective radius of interaction between the proton and deuteron during elastic scattering was found to beR=(2·25±0–10)×10^–13 cm.Last but not least, he thanks the management of the Joint Institute of Nuclear Research in Dubna for irradiating the emulsions and M. G. afranová for valuable advice and unstinting help in irradiating the emulsions.     

罗丹明6G缔合微粒共振散射光谱法测定过氧化氢

在0.020mol.L-1HCl-4.0×10-4mol.L-1KI-1.6×10-5mol.L-1Mo(Ⅵ)介质中,罗丹明6G(RhG)在540nm处有1个荧光峰,在540nm处有1个同步荧光峰。当有H2O2存在时,H2O2与过量的I-反应生成I3-,I3-与RhG形成缔合微粒,在320,400,595nm处产生3个共振散射(RS)峰;而在540nm处荧光峰猝灭。H2O2浓度在0.068~34μg.mL-1范围内与400nm波长处的共振散射光强度呈线性关系。据此建立了一个测定水中H2O2的共振散射光谱分析法。光谱研究结果表明,(RhG-I3)n缔合微粒和界面的形成是导致体系RS增强和荧光猝灭的根本原因。     

能量在10Bev以下的π-N,p-N和p-N相互作用

本文试把到写稿时为止(1961年3月底)的一切关于π-N,p-N和p-p的作用和入射粒子能量在几百Mev.至10Bev.范围以内的实验工作予以报导和总论。举凡关于这些作用的总截面、弹性散射截面和非弹性散射截面,都经收集整理,并加以分析。这些截面随能量的增减而变化的情况,都以曲线表达,并且与理论结果作出比较。曲线中有几个重要和有趣之点,也予以指出。在π-N作用中的几个共振峯和关于他们的理论解释,也经较详细的叙述。在弹性散射方面,我们将微分截面的角分布和理论作了比较。在非弹性散射方面,我们把多重产生、动量分布、角分布、横动量和它们与入射粒子能量的关系,都加以分析和讨论。我们特别注意和讨论了下列二种情况:在π-p作用时,质子总是向后散射;而在p-p作用时,两个质子总是不各向均匀地但向前后对称地散射。这种现象被称为质子的“边缘”碰撞。我们认为,这些和其他事实都可能表明了在质子内的确有“核心”的存在,而且这个“核心”非常的小,它的直径比0.4×10^-13厘米要小得多。     

Measurement of the transverse beam spin asymmetry in elastic electron-proton scattering and the inelastic contribution to the imaginary part of the two-photon exchange amplitude

We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A( perpendicular), at two Q2 values of 0.106 and 0.230 (GeV/c)(2) and a scattering angle of 30 degrees 相似文献   

一种二进制降能器设计方法

为提升在中国原子能科学研究院的100 MeV质子回旋加速器上进行多能点质子单粒子效应实验的效率,针对该加速器提供的100 MeV质子设计了一种二进制降能器.降能器包括6片铝降能片,厚度分别为0.5,1,2,4,8,16,32 mm,即后一片厚度均为前一片的2倍.提出相对厚度的概念,此概念也可用来表示产生的质子能点的次序以及降能器的状态或操作.降能器产生的9.69 MeV以上的61个质子能点间隔在0.84—4.09 MeV之间,且能量岐离均在10%以下,散射角半高宽均在45 mrad以下,基本可满足质子单粒子效应实验的要求.对加速器直接提供的质子的能量精度对降能器产生的质子能点的影响进行分析,发现经降能器产生的质子能量越低,其影响也就越大.此外,降能器对加速器直接能够提供的70—100 MeV能区的质子也是适用的,且可通过增加降能片数量的方式来获得更加连续化的质子能点.本文提出的降能器设计方法简单有效,具有较强的借鉴价值.     

Asymmetry in the scattering of protons on polarized deuterons at 1.21 GeV/c

By using a polarized deuteron target we have measured the asymmetry in the differential cross section for elastic scattering of protons on deuterons and for quasi-elastic scattering of protons on protons bound in deuterons between the two states of opposite polarization, normal to the scattering plane of the initial deuteron. The beam momentum was 1.21 GeV/c. It is checked that the neutrons bound in the deuterons are polarized to approximately 20%.     

Measurement of strange-quark contributions to the nucleon's form factors at Q(2) = 0.230 (GeV/c)(2)

We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.     

NMR and inelastic incoherent neutron scattering (IINS) studies of monohydroxy-17 and -21-substituted derivatives of progesterone

Internal dynamics of 17- and 21-substituted progesterone derivatives was studied by the methods NMR, inelastic incoherent neutron scattering (IINS) and quantum chemical calculations. Comparison of the computer simulation of the phonon density of states (PDS) spectrum performed by the density functional theory (DFT) method with the spectrum obtained after a transformation of the experimental results permits an interpretation of subsequent modes. Only for 17OH prg the second moment of NMR line decreases to 10 G2 near room temperature, most probably because of the oscillations about direction of inter-molecular hydrogen bond. Significant mobility of protons in this compound is also confirmed by a low intensity of the elastic peak in INS and broadening of this spectrum.     

Coherent neutron scattering by light water (H2O) and a light-heavy water mixture (64 per cent H2O/36 per cent D2O)

Measurements have been made, with high statistical accuracy, of the differential scattering cross-section for 1·06 Å neutrons by light water and a special mixture of light and heavy water at 22°C. For light water, the structure in the scattering pattern is attributed mainly to coherent scattering; a structure factor has been obtained over a limited range of momentum transfer. For the chosen mixture, the protons and deuterons give no contribution to the coherent scattering and a structure factor has been obtained which corresponds very well to the oxygen-nucleus structure factor obtained from X-ray data. The results show the desirability of extending these high accuracy measurements using isotopic substitution methods as a means of obtaining the three partial structure factors for water. The method of isotopic mixtures is applicable to a wide range of proton containing liquids.     

Most probable and average energy losses of the beam of monoenergetic charge particles with average and low energies at multiple scattering

The results of statistical modeling of the discrete process of multiple inelastic scattering are presented. This process is modeled to find the most probable and average energy losses of a beam of charged particles (electrons and protons) passing through a material layer with a given thickness. The proposed approach is based on determining the most probable energy loss at single small-angle scattering, on including the effect of the statistical probability on this quantity at multiple scattering, and on determining the average number of inelastic interactions for particles in a film with a known thickness. The dependence of the particle energy lost during interaction with atomic electrons on their relative motion is taken into account for low-energy particles. A new interpretation is offered for the parameter J in the logarithmic term in the formulas for the average and most probable energy losses of charged particles. A computational scheme for this parameter as an average potential energy of atomic electrons is given.     

Chemical exchange of hydroxyl protons in quercetin measured by pulsed field gradient NMR

The diffusion behavior of hydroxyl protons (OH) in quercetin in 100% DMSO-d₆ (deuterium dimethylsulfoxide) and a 90% DMSO-d₆ solution containing 10% H₂O was investigated with 600 MHz ¹H pulsed field gradient (PFG) nuclear magnetic resonance (NMR). Only resonances of the 5-hydroxyl protons (OH5) were well resolved in NMR spectra of quercetin for all solutions under study. This phenomenon is explained by the intramolecular hydrogen bonding between OH5 protons and the 4-carbonyl oxygen (CO4). During diffusion experiments, the OH5 protons showed a biexponential diffusion decay, indicating an exchange process with water. As water content in the solvents increased, the lifetime (τ _q) of the OH5 protons decreased from 96.7±10.0 ms in 100% DMSO-d₆ to 14.3±1.4 ms in the 90% DMSO-d₆ solution containing 10% H₂O, indicating an increase in the exchange rate (k _q = l/τ _q) of the OH5 protons. This study demonstrates that the diffusion approach with PFG-NMR is much faster and easier for estimating the short lifetime or fast exchange rate of hydroxyl protons in quercetin.