共查询到19条相似文献,搜索用时 156 毫秒
1.
采用反冲离子飞行时间-散射离子位置灵敏符合测量技术,测量了能量范围在0.7 v0—4.4v 0( v0为玻尔速度)的碳离子 Cq+( q=1—4)与He原子碰撞过程不同出射道靶原子的双电离与单电离截面比 R,包括入射离子不损失电子(直接电离)的出射道( Rq,q),入射离子俘获一个电子的出射道( Rq,q-1)和入射离子损失一个电子的出射道( Rq,q+1),并研究了 R随入射C离子的能量及电荷态的变化关系.实验表明,对给定电荷态的入射离子,靶原子的双电离与单电离截面比 R与出射道有很强的依赖关系,即 Rq,q< Rq,q+1< Rq,q-1.直接电离出射道截面比 Rq,q与入射离子电荷态几乎无关,而入射离子俘获一个电子的出射道和损失一个电子的出射道靶原子双电离与单电离截面比 Rq,q-1和 Rq,q+1却与入射离子电荷态有很强的关系.采用原子极化理论和电子屏蔽与反屏蔽作用对实验结果进行了解释.
关键词:
离子-原子碰撞
电离
截面比 相似文献
2.
本文提出了予测稠苯芳杂环及其烷基链上质子化学位移的计算方法。
将稠苯芳杂环化合物用凯库勒式表示,计算式为为需考虑的苯环内的乙烯基效应。σ mi,ci为各苯环的环流效应。 σ1,Hc为各芳杂环的屏蔽效应,对杂环上质子它就是该单独芳杂环上相应质子的 δ值,对苯环上质子要将它分解为各结构因素的效应,即: σ1,He=(1/2) d-1δx=y(或 σz)+ σc-c· σm,H.
σx-y与 σz为杂原子或其基团的屏蔽效应, σc=c为存在于芳杂环中的乙烯基的效应, σm,Hc为芳杂环的环流效应, d为对不同质子所考虑的键数。有取代基时需考虑取代基的效应。计算环上烷基质子的公式为: δ= σp,CH3+ ασc,CH3+ βσt,CH3+ σl,G
σl,G为稠苯芳杂环基的某级效应。 相似文献
3.
本文提出了予测稠苯芳烃及其衍生物的环上和烷基链上质子化学位移的计算方法。
将稠苯芳环化合物用凯库勒式表示,用下式计算:
δ= σj.c-c+ σmi.ci
σj.c-c为各种乙烯基的效应。 σmi.ci,为各个苯环的六电子 π轨道的净环流效应,其计算式为:
σm.e=(1/2) m×1,52 m=n-u
m为净环流效应级数,等于质子到该苯环相隔的键数n减其中的顺式键数u。
在菲环和类似菲环的4,5位与9,10位质子需考虑菲环效应。蒄环上的质子需考虑蒄环效应。有取代基需考虑取代基的效应。
计算环上烷基质子的公式:
δ= σp.CH3+ ασ2.CH3+ βσt.CH3+ σi.G
此公式在作者以前的文章中己经报道。 σi,G为稠苯芳基的某级效应。 相似文献
4.
研究了Tm 3+/Ho 3+共掺TeO 2-WO 3-ZnO玻璃在808 nm激光二极管抽运下的2.0μm发光特性及Tm 3+与Ho 3+之间的能量传递.应用Judd-Ofelt理论计算了Ho 3+在碲酸盐玻璃中的谱线强度参量 Ωt ( t=2,4,6)、自发辐射概率 Ar、辐射寿命 τr等.计算了Ho 3+的吸收截面 σa( λ)和受激发射截面 σe( λ).结果表明:碲酸盐玻璃中Tm 3+→Ho 3+正向能量传递系数大约是Tm 3+←Ho 3+反向能量传递系数的18倍.Ho 3+离子的 5I 7能级的寿命为3.9ms,2.0μm处的最大发射截面为9.15×10 -21cm 2.在0.5mol% Tm 2O 3和0.15mol% Ho 2O 3共掺的碲酸盐玻璃中能获得2.0μm的最大增益.通过比较氟化物、碲酸盐和镓铋酸盐重金属氧化物等玻璃中Ho 3+的量子效率 η, σe× τm值和增益系数 G( λ)等,发现Tm 3+/Ho 3+共掺碲酸盐玻璃是一种理想的2.0μm激光器用基质玻璃.
关键词:
2.0μm发光
能量传递
增益
碲酸盐玻璃 相似文献
5.
应用重整化群计算最短轨道模型的生长几率分布{ Pα,i}及其构型权重 Cα(2×2原胞和3×3原胞),从而得出多分形热力学的配分函数 Z( q, L),自由能 F( q, L),能量 E( q, L),比热 c( q, L)和广义维数 Dq,结果表明该模型在 q= qc≈0处发生相变,即当 q < qc时,生长几率分布{ Pα,i}不具有多分形性质。 相似文献
6.
用密度泛函理论的B3LYP方法,分别以6-311++g(df,3pd),6-311g(3d,3p)和6-311++g(3df,3pd)为基函数对NF分子、NF +和NF -离子基态进行几何优化和频率计算,并进行单点能扫描计算.用最小二乘法拟合得到NF X( X=-1,0,+1)分子离子基态的Murrell-Sorbie势能函数.利用得到的解析势能函数计算出的NF分子和NF +离子基态光谱常数( Be, αe, ωe, ωeχe)与实验值符合很好.首次得到NF -离子基态的光谱常数( Be, αe, ωe, ωeχe)和力常数( f2, f3, f4),为NF-离子基态的后期研究提供理论参考. 相似文献
7.
定义了一类相空间中的准几率分布函数系,这个准几率分布函数系直接建立在具有更加广泛意义的量子相空间Schr?dinger方程解的基础之上,其中定义 α= αp-i?q和 α=(1- α) q+i?p.发现了两个有趣的关系.(1)建立的量子相空间Schr?dinger方程的解实际上是对函数 φ(λ)exp[i(1- α) qp]做窗口Fourier变换.(2)这个窗口函数 g(λ)起着选择窗口形式的作用,而且不同的窗口对应着不同的分布函数.当 g(λ)是一个代表Gauss窗的Gauss函数的时候,准几率分布函数就是一个类似于Husimi的分布函数 fHLα( q, p);当 g(λ)是一个表示椭圆的复函数时,准几率分布函数就是一个椭圆分布函数 fEα( q, p);再在 g(λ)为复函数的基础上附加 α=0,就可得到标准序分布函数 fS( q, p)、反标准序分布函数 fAS( q, p)和Wigner分布函数 fW( q, p),此时 g(λ)表示高度为1/12π?而长度为λ的矩形窗.
关键词:
窗口Fourier变换
相空间
Wigner分布函数 相似文献
8.
报道了Tm 3+/Ho 3+共掺的镓铋酸盐玻璃14Ga 2O 3-25Bi 2O 3-20GeO 2-31PbO-10PbF 2玻璃1.47μm(S波段)发光和能量传递特征,应用Judd-Ofelt理论计算了玻璃的强度参数 Ωt( t=2,4,6),自发辐射概率 A、荧光分支比 β,荧光辐射寿命 τ等各项光谱参数以及有效荧光线宽Δ λeff和峰值发射截面 σpeake.通过测量荧光光谱和荧光寿命研究了Ho 3+离子掺杂浓度对Tm 3+离子1.47μm波段发光性能的影响,分析了Tm 3+和Ho 3+之间的能量传递过程.结果表明一定浓度内Ho 3+的共掺迅速降低了Tm 3+: 3F 4能级的粒子数,而对 3H 4能级粒子数影响不大,从而降低了 3F 4和 3H 4能级间布居数反转的难度,极大地提高了1.47μm发光效率.研究表明镓铋酸盐玻璃是适用于S波段光纤放大器的一种潜在基质材料,而掺杂一定浓度的Ho 3+离子有利于提高Tm 3+离子在1.47μm波段的发光效率.
关键词:
重金属氧化物玻璃
光谱性质
3+/Ho 3+离子')" href="#">Tm 3+/Ho 3+离子
能量传递 相似文献
9.
在扩散限制凝聚模型基础上,采用Monte Carlo方法模拟了磁耦合作用随粒子间距离幂次变化的磁性粒子动力学凝聚过程.重点研究了在不同幂指数 α值下团簇在生长过程中,即随着粒子数 N的增加,团簇平均耦合能 Ec( N)的演化过程.模拟结果表明:对于 α≥5时, Ec( N)随着粒子数 N的增加变化较小;当 α=2时, E
关键词:
扩散限制凝聚模型
幂次相互作用
耦合能 相似文献
10.
对铀原子和氮原子分别使用相对论有效原子实势和6-311+G(d)基组, 采用优选的密度泛函B3P86方法, 研究了铀本身产生自辐射场(-0.005–0.005 a.u.)作用下UN 2基态分子的能隙 Eg和谐振频率 ν. 结果表明: UN 2分子在自辐射场中反对称伸缩振动频率 ν3( σg)和对称伸缩振动频率 σ1( σg)与实验值1051.1 cm -1和1008.3 cm -1 基本符合; Eg随自辐射场场强的增大而趋于减少, 占据轨道的电子容易被激发至空轨道而形成激发态; UN 2分子在自辐射场中趋于不稳定, N 2, O 2等更容易扩散到表面内层而腐蚀铀表面, 加剧了铀在自辐射场中的腐蚀. 相似文献
11.
用传统量子力学方法研究了横截面为正三角形的腔内氢负离子光剥离, 得到了光剥离截面随能量变化的解析表达公式. 该公式还给出了剥离截面的阈值行为. 进一步研究发现, 当氢负离子处于正三角形一角附近时, 用量子力学方法得到的结果与氢负离子处于60°角域内时使用闭合轨道理论得到的结果一致. 相似文献
12.
A method for internal calibration of ESCA (XPS ) spectra is described that permits the use of a simple relation between binding energy ( Eb) and atomic charge ( q) : Eb = kq + Eb0. This relation has been shown to hold for a large number of elements. So far the relation for carbon has, however, not been very well established. A method is now described that allows the use of carbon charges determined from Eb, vs. q correlations for other elements and has also made it possible to establish a linear relation for carbon. The method does not use carbon charges determined directly from quantum chemical calculations. As an essential part of this procedure we investigated empirically the possible relation between the difference between the gas phase calibration standard and that for the same element in the solid state, “a”, and the molar polarizability of the substance, P. It was found that “a” decreases with increasing polarizability, tentatively as a=4.15+8.30 P−1/3. Therefore, knowledge of the polarizability of carbon-containing molecules from the literature made it possible to determine “a” and then the charge of all other atoms in the molecule. In this way a set of Eb and qc date was obtained. These data were complemented by another set using theoretical qc snd solid state Eb of phenyl compounds previously made. The results of the investigation show a linear relation between Eb(Cls) and qc valid for the solid state: Eb,(Cls) = 4.68 qc + 286.2 eV with a correlation coefficient of 0.945. This brings the previously obtained k value for carbon, which seemed anomalously high, down to a value of similar magnitude as for other light elements. 相似文献
13.
The classical Hamiltonian H = p2/2 m + ε( q2/2)Σδ[ s-( t/ T)] has an integrable mapping of the plane, [ qn+1, pn+1]= [ qn+1+ pn, qn+2 pn], as its equations of motion. But then by introducing periodic boundary conditions via (mod 1) applied to both q and p variables, the equations of motion become the Arnol'd cat map, [ qn+1, pn+1] = [ qn + pn, qn + 2 pn], (mod 1), revealing it to be one of the simplest fully chaotic systems which can be derived from a Hamiltonian and analyzed. Consequently, we here quantize the Arnol'd cat and examine its quantum motion for signs of chaos using algorithmic complexity as the litmus. Our analysis reveals that the quantum cat is not chaotic in the deep quantum domain nor does it become chaotic in the classical limit as required by the correspondence principle. We therefore conclude that the correspondence principle, as defined herein, fails for the quantum Arnol'd cat. 相似文献
14.
Quasiclassical trajectory (QCT) calculations have been performed for the abstraction reaction, D' +DS( v = 0, j = 0)→D'D+S on a new LZHH potential energy surface (PES) of the adiabatic 3A' electronic state [Lü et al. 2012 J. Chem. Phys. 136 094308]. The collision energy effect on the integral cross section and product polarization are studied over a wide collision energy range from 0.1 to 2.0 eV. The cross sections calculated by the QCT procedure are in good accordance with previous quantum wave packet results. The three angular distribution functions, P( θr), P(φ r), and P( θr,φ r), together with the four commonly used polarization-dependent differential cross sections ((2π/σ)(ds 00/dω t), (2π/σ)(ds 20/dω t), (2π/σ)(ds 22+/dω t), (2π/σ)(ds 21-/dω t)) are obtained to gain insight into the chemical stereodynamics of the title reaction. Influences of the collision energy on the product polarization are exhibited and discussed. 相似文献
15.
The momentum transfer dependence ( q=0.20−0.59 fm −1) of the recently discovered M1 transition from the Jπ=1 + state at Ex=5.846 MeV to the ground state of 208Pb has been studied with high-resolution inelastic electron scattering. The experimental data are compared to results of RPA calculations which include tensor correlations. The influence of these correlations and of the interference of proton and neutron contributions on the M1 transition will be discussed. 相似文献
16.
提出两差分格式求解时间分数阶亚扩散方程.两个格式都是绝对稳定的,收敛阶均为 O( τq+ h2),其中 q( q=2- β或2)与方程解的光滑性有关, β(0 < β < 1)是分数阶导数的阶、 τ和 h分别是时间和空间方向步长.数值实验验证了理论结果的正确性,并与其他方法进行比较,显示了本文方法的有效性和精确性. 相似文献
17.
The reaction e + p → e + π 0 + p was measured near the one pion threshold, detecting the final electron and proton in coincidence for values of q2 = 0.2, 0.4 and 0.6 GeV 2. The slope of the cross section at threshold is determined. The data are compared with those of the e + p → e + π + + n reaction, measured simultaneously, and with the results of pseudovector Born approximation and with dispersion theoretical calculations. 相似文献
18.
采用分子动力学模拟计算方法,考察具有较高层错能的Al纳米线沿不同晶向的力学行为和变形机制。在相同计算条件下与具有较低层错能的Ni、Cu、Au和Ag等FCC金属纳米线进行比较。结果表明:在力学行为方面,Al纳米线的弹性模量呈现明显的结构各向异性,满足 E[111] > E[110] > E[100]的关系,这一关系在FCC金属纳米线中普遍成立;Al纳米线的屈服应力随晶向呈现 σy[100] > σy[111] > σy[110]的关系,这一关系在具有较低层错能的FCC金属纳米线中不具有普遍性,这与体系中位错形成机制密切相关。根据拉伸变形过程微观结构的演变规律,阐明Al纳米线不同晶向的变形机制,并与具有较低层错能的Ni、Cu、Au和Ag等FCC金属纳米线的变形机制进行比较。结果表明,对于尺度较小的高层错能Al纳米线,Schmid因子和广义层错能均难以准确预测其变形机制。 相似文献
19.
The spectra of electrons scattered inelastically from 4He have been measured at incident energies from 150 MeV to 400 MeV for scattering angles from 38° to 90°. Through the use of a liquid 4He target, a high momentum resolution (≈0.25%) was obtained, and the 20 MeV 0 + state of the -particle was observed for the first time in electron scattering. The excitation energy and the total width of this state were determined and are in good agreement with the results from other experimental methods. It was found that the total disintegration cross section appears be smaller than 2(σ p+σ n) by more than an order of magnitude at the lowest q2(≈ 0.33 fm −2). In earlier work the assumption of a total cross section of 2(σ p+σ n) was found to be quite accurate for higher q2. As a new result, the partial radiative width for the 0 + state is determined to be Γ rad = 1.1±0.3 meV. 相似文献
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