CHCl3电子吸附速率常数的离子迁移谱

利用电晕放电离子迁移谱, 使用高纯氮气作为载气和迁移气体, 研究了电场强度在200～500 V/cm变化时CHCl₃的解离电子吸附速率常数, 得到样品所对应的电子吸附速率常数为1.26×10^-8～8.24×10^-9 cm³/(molecules s)．利用该装置测量了固定电场下,样品的电子吸附速率常数与样品浓度之间的关系．此外利用所获得的离子迁移谱图得到了不同电场强度下Cl^-与CHCl₃之间的离子分子反应速率常数.     

用云母弯晶谱仪探测Z箍缩等离子体X射线光谱

 为了研究Z箍缩等离子体辐射的X射线光谱,研制了可用于“阳”加速器上探测宽频谱范围的X射线椭圆弯曲晶体谱仪。该谱仪晶体分析器采用云母材料,椭圆焦距为1 350 mm,离心率为0.948 5,覆盖布拉格范围为30°~60°,可探测X射线波长范围为0.10~1.73 nm(0.86~1.00 nm除外),用X射线胶片接收光谱信号。探测实验在中国工程物理研究院“阳”加速器上进行,实验结果表明:谱仪获取了氩的类氢共振线L_ya及其伴线、类氦共振线(1s2p¹P₁-1s2¹S₀)w线及磁四级M₂2跃迁(1s2p³P₂-1s²¹S₀)x线、互组合跃迁(1s2p³P₁-1s²¹S­₀)y线、禁戒谱线(1s2p³S₁-1s²¹S₀)z线和K­_-a线,谱线分辨率达到564。实验证明弯晶谱仪适合于Z箍缩等离子体X射线光谱学诊断。     

在等离子体中镁离子谱线MgⅡλ4481?的宽度和位移

本工作测量了MgIIλ4481?(3²D—4²F)在电子数密度为7×10¹⁶—3.1×10¹⁷电子数/cm³范围内的谱线轮廓和位移。采用振荡型电容放电作为光谱光源。在光源中引入水汽,由测量H_β谱线宽度来定电子数密度。观测结果指出,H_β的实验轮廓和Griem-Kolb-Shen的计算结果符合颇好。实验发现MgIIλ4481?谱线向紫方位移,并正比于微观电场的平方;由此定出一个经验上的二级斯塔克效应常数C₄=5.0×10^-14cm⁴/sec。该谱线的轮廓宽度和标准微观电场之间也有平方正比的关系。发现在本实验条件范围内,宽度和位移的比值γ/△保持为常数,其值为γ/△=10.4±0.6。由于谱项4²D的二级斯塔克效应的干扰而产生上能级4²F位移的理论计算虽能说明谱线位移和微观电场间的平方正比关系,但数值偏小于实验结果,指出还有电子贡献的部分。把光谱线的宽度和Lindholm理论公式及Griem等的近似公式作了比较;简单的估计指出,实验结果和后者符合较好。     

1.315μm附近CO2的高分辨率吸收光谱

 利用可调谐激光长程吸收光谱测量系统，记录到1.315μm附近高气压（80kPa和40kPa）CO₂的高分辨率吸收光谱，拟合分析获得谱线参数，结果与HITRAN 2k的数据基本一致。用程差法测量了绝对吸收，氧碘激光频率(7 603.138 5cm^-1)的总吸收截面为(0.23~0.29)×^-24cm²。仅计算谱线吸收的吸收截面为0.18×10^-24cm²。在1.315μm波段COCO₂存在连续吸收，吸收截面为(0.05~0.11)×10^-24cm²。还讨论了测量误差问题。     

Al激光等离子体电子温度的时间分辨诊断

 将门控分幅相机与平面晶体谱仪耦合，构成时间分辨光谱测量系统，对Al激光等离子体的K壳层发射谱进行测量，获得了相对入射激光延迟约1ns，积累时间约200ps的光谱信号。利用稳态碰撞-辐射平衡（CRE）近似条件下的等离子体光谱辐射动力学模型，给出了Al激光等离子体Ly-β线与He-β线强度比以及Ly-γ线与He-γ线强度比与电子温度的函数关系。在此基础上，根据实验谱线强度比，得到激光强度为2.319×10¹⁴，1.937×10¹⁴和3.946×10¹⁴ W/cm²时，等离子体冕区电子温度分别为1.190(1±27%)，1.165(1±27%)和1.525(1±27%)keV。     

在J/ψ衰变与ρ→π+π–π0衰变中的ρ–ω干涉

通过分析J/ψ→π⁺π^-π^{0π0来研究ρω干涉.利用描述J/ψ衰变的一般的唯象模型对PDG-2002关于J/ψ衰变到PP和PV的实验数据做了拟合(P表示赝标介子,V表示矢量介子) ,得到ρ0→π+π-π0反常大的分支比～10-3—10-2.理论的分析结果也与这一反常大的分支比相符合.同时,得到了合理的ηη′混合角和组分夸克质量比:θ=-19.68°±1.49°,m_u/m_s≈0.6 .}     

高性能MgB2长线材制备及性能表征

采用原位粉末装管工艺，分别以Mg粉(99.5%)，无定形B粉(99.9%)为原料，以纳米SiC(10—30nm)作为掺杂材料制备铁基MgB₂线.首先将已混合的原料在丙酮介质中球磨，真空干燥后，将粉末填入铁管内，然后通过孔型轧制、旋锻和拉拔等冷加工工艺得到11m长外径Ф1.75mm铁基MgB₂超导线.用扫描电镜，电子能谱，X射线衍射仪和超导量子干涉仪测试发现，样品微观结构整齐，晶粒大小均匀，内部仅含微量MgO，T_C(onset)=35.1K，ΔT_C＝5.3K.纳米SiC掺杂后，其中C造成MgB₂晶格畸变，形成有效磁通钉扎中心，C元素在MgB₂中分布均匀.标准四引线测试结果表明，11m线均分10段后，各点的J_c(4.2K,10T)均超过1.0×10⁴A/cm^{2，最高值达到1.2×104A/cm2.在10—18T范围各点临界电流值分布均匀，变化率小于10%.}     

电子通量对ZnO/K2SiO3热控涂层光学性能的影响

 研究了电子通量对ZnO/K₂SiO₃热控涂层光学性能的影响。分别采用通量为5×10¹¹/cm²·s，8×10¹¹/cm²·s，1×10¹²/cm²·s 和5×10¹²/cm²·s的电子对试样进行辐照。电子辐照下涂层的光学性能发生了退化，并且发现了退化涂层在空气中的“漂白”现象。分析了ZnO/K₂SiO₃热控涂层光学性能的退化机制，同时讨论了电子通量对太阳光谱吸收系数的影响。实验结果发现，在5×10¹¹～1×10¹²/cm²·s的电子通量范围内，电子通量对ZnO/K₂SiO³热控涂层光学性能的影响相同。因此在这个电子通量范围内，采用加速地面试验来模拟空间的电子辐照效应是有效的。     

87Rb D1线法拉第反常色散光学滤波

为了得到在高背景噪音下对弱信号光的提取,实验研究了基于⁸⁷Rb D₁线5S_1/2F=2→5P_1/2 F'=1跃迁的795 nm法拉第反常色散光学滤波器.充铷的样品池所含⁸⁷Rb的比例高于自然铷,样品池处在均匀的磁场中并且夹在两个相互正交的偏振片之间.入射的探测光通过样品池,与原子相互作用,由于法拉第旋转效应实现滤波功能.改变实验条件,透射结果随之明显变化.当温度从340 K升高到360 K,透射谱的变化情况被细致记录,并且分析了导致透射情况变化的原因.在适当的工作温度以及磁场条件下,得到线宽为约220 MHz的超窄带透射谱线,谱线透过率约为48%.⁸⁷Rb D₁线的实验结果优于⁸⁵Rb的吸收线.     

空气放电非平衡等离子体的模拟计算

 基于空气放电非平衡等离子体动力学,对空气放电进行了数值计算,分析了放电后等离子体中的主要粒子（N₂(v6),N₂(A3),O₂(a1),O和O₃）数密度随起始温度、电子数密度和约化场强的变化趋势。计算结果表明,随着初始温度的升高,空气放电产生的粒子数密度增加。温度为300 K时,放电产生的O原子数密度最大值约为4.90×⁷ cm^-3,而当温度升高到400 K和500 K时,O原子数密度的最大值则相应地增加到5.2×10¹⁰ cm^-3和5.51×10¹⁰ cm^-3。约化场强的影响与温度类似,其中氮气的振动激发态N₂(v6)数密度随约化场强的变化幅度不明显。电子数密度增加,粒子数密度大幅增加,氮分子的激发态N₂(A3)粒子数密度与电子数密度保持严格的线性关系。     

Anomalous Phases in Cavity-Free 240 GHz Pulsed ENDOR Spectra of 1.44 GeV Xe-Irradiated LiF

Paramagnetic centers generated by swift heavy ion irradiation of LiF crystals could be identified as electrons trapped at regular anion vacancy sites (F centers). Well-resolved electron-nuclear double resonance (ENDOR) spectra resulting from the hyperfine interaction with ⁷Li and ¹⁹F nuclei located in six different shells could be recorded. In order to preserve the millimeter-sized crystals, a cavity-free setup was used for the ENDOR experiments at an electronic Larmor frequency of 240 GHz. Apparently even under conditions of extremely high local energy loss in the ion track, the local density of persistent F centers is still sufficiently low to prevent distortions of the ionic crystal. The spread of hyperfine coupling constants was less than 5 %. Neither in electron paramagnetic resonance (EPR) nor in ENDOR spectra there was evidence for different types of paramagnetic centers. When performing ENDOR by applying the radiofrequency pulse directly after the 3-pulse Mims-type microwave sequence, an anomalous ENDOR effect was observed. The observed “positive” and “negative” ENDOR response can be attributed to efficient hole and anti-hole formation in the inhomogeneously broadened EPR spectrum and can be used to determine the sign of hyperfine coupling constants.     

Crystal field effects on the magnetic and hyperfine properties of Yb3+ in ytterbium ethylsulfate

The magnetic and hyperfine properties of Yb³⁺ in Yb(C₂H₅SO₄)₃·.9H₂O have been studied using the crystal field (CF) obtained from an analysis of the observed absorption spectra of the crystal. The principal magnetic susceptibilities are in reasonable agreement with those observed both at liquid oxygen and liquid helium temperatures. The observed reversal of magnetic anisotropy at 17.7K is also corroborated. The Schottky heat capacity shows a peak at around 40K. The magnetic hyperfine field due to the 4f electrons at the nucleus is found to be 1.79MG. The hyperfine heat capacity C_N has a Schottky anomaly at about 25 mK. Above 1K, in the liquid helium range, C_N follows a simple T^?2 law as observed by Cooke et al. It is concluded that in the rare earth ethylsulfates a single suitable CF gives a good account of the various properties from room temperature down to liquid He temperatures.     

Temperature Dependence of Hyperfine Interaction for 15N Nitroxide in a Glassy Matrix at 10–210 K

Principal ¹⁵N hyperfine interaction (hfi) values in ¹⁵N-substituted nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl dissolved in nematic liquid crystal 4-pentyl-4′-cyanobiphenyl (5CB) were measured in a wide temperature range of 10–210 K, for 5CB frozen to a glassy state. X-band continuous-wave electron paramagnetic resonance (CW EPR) and pulse X- and Q-band ¹⁵N electron-nuclear double resonance (ENDOR) techniques were employed. To avoid microwave saturation at low temperatures in CW EPR studies, a holmium complex Ho(Dbm)₃Bpy (where Dbm is dibenzoylmethane and Bpy is 2,2′-bipyridine) was added. X- and Q-band ¹⁵N-ENDOR data have shown that the nitroxide hfi tensor is axially symmetric. The combination of data from all techniques allowed us to obtain the temperature dependence of isotropic and anisotropic parts of the nitroxide hfi tensor. Above ~100 K, a linear dependence of the anisotropic hfi value was observed, whereas below 30 K it was found to be nearly temperature independent. Such a behavior can be interpreted using the model of restricted orientational motions (librations) of a spin probe in a glassy matrix, with quantum effects occurring at low temperature (“freezing” of the librations). The energy quantum for the libration motion estimated from the temperature dependence of hfi of the spin probe is 84 cm^?1. Low-frequency Raman spectra of 5CB were also obtained, which provided the mean vibrational frequency of 76 cm^?1 for glassy 5CB.     

束缚施主电子与Si29核超精细作用的各向异性

本文利用Si中浅能级施主的有效质量波函数,计算了束缚施主电子与Si²⁹核超精细作用的等效自旋哈密顿量。超精细作用中不同谷的Bloch函数之间,相干效应非常明显,超精细作用的各向异性主要是由谷间相干效应决定的。在强场近似下求出了Si²⁹核的核磁共振频率的表示式,定量地解释了Feher的实验结果,并且可以由实验定出谷间磁偶极相互作用矩阵元。从正交干面波的观点出发进行了计算,与实验结果比较定出了导带底布洛赫函数中2P心态波函数的组合系数的大小为0.20。指出了利用双共振方法及其压力效应有可能测定导带底的波矢及有效质量波函数的各向异性分布。     

Study of combined magnetic and electric hyperfine interactions for cadmium in Dysprosium by time differential perturbed angular correlations

The combined magnetic and electric hyperfine interaction at the site of a¹¹¹Cd impurity in magnetically ordered Dysprosium has been investigated as a function of temperature by time differential perturbed angular correlation measurements. Three different phases have been found in metallic Dy with transition temperatures of 85 and 179 °K in agreement with the results of bulk material measurements. In the paramagnetic phase above 179 °K a pure electric quadrupole interaction has been observed. The various contributions to the electric fieldgradient are analyzed and it is shown, that the dominant contribution comes from the conduction electrons. In the ferromagnetic phase which extends from 0 to 85 °K the magnetic hyperfine field at the site of¹¹¹Cd has the same temperature dependence as the spontaneous magnetization. The value of the hyperfine field at 4.2 °K is ¦H _eff¦=(221 ± 4) kG. At 85 °K a transition to the antiferromagnetic phase of Dy occurs, which shows a hysteresis of the transition temperature. In the antiferromagnetic phase the temperature dependence of the hyperfine field deviates considerably from the magnetization curve. It is suggested that this deviation might be due to a temperature dependence of thes-f exchange interaction.     

High-field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions

In this work D-band pulsed electron paramagnetic resonance was used to record the field-sweep spectra of several Gd³⁺ complexes in glassy water-methanol solutions. These spectra were analyzed by a specially developed stochastic superposition model that predicted the essential features of the distribution of the crystal field interaction (CFI) parameters in glassy systems. As a result of this analysis, the CFI distributions for the studied complexes were evaluated. The D-band Mims¹H electron-nuclear double resonance spectra were free from CFI-related distortions, which allowed us to accurately determine the hyperfine interaction (HFI) parameters for water ligand protons and to unequivocally establish that the HFI distribution is solely related to the distribution of the Gd?H distances.     

Characterization of electron spin exchange interactions in cellulose chars by means of ESR,1H NMR,and Dynamic Nuclear Polarization

Cellulose chars heat treated under nitrogen atmosphere for six hours over a range of heating temperatures from 250 to 1000°C were studied by ESR, broadline¹H NMR, and Dynamic Nuclear Polarization (DNP). Chars heated below 450°C exhibited DNP enhancements predominantly due to the solid state effect resulting from static electron-nuclear spinspin interactions, while chars heated at higher temperatures exhibited Overhauser enhancements, which result from time dependent interactions. It was found that, while the maximum number of unpaired electrons was obtained at a heating temperature of 700°C, the maximum Zeeman and rotating-frame¹H relaxation rates were achieved at much lower temperatures. Moreover, small Overhauser enhancements were observed even at the lower heating temperatures, where the time dependent electron-nuclear interactions are expected to be minimal, and the solid state enhancements decrease more rapidly than expected for samples heated above 350°C. These effects are explained in terms of a distribution of rates of electron-electron spin-exchange interactions. The charred and carbonized cellulose samples provided a set of solids in which the number of unpaired electrons varied over a large range and exhibited a broad distribution of spin-exchange rates. It was shown that DNP-NMR is a powerful method for probing this distribution, and for detecting small fractions of rapidly exchanging and static electrons.     

Theory of cyclotron resonance width for electrons inelastically scattered by phonons

The cyclotron resonance width for a semiconductor under extreme high fields is calculated with the assumptions that electrons are scattered by acoustic phonons inelastically. The numerical results are in very good agreement with the recent experiments on Ge by Miura et al. (T ～ 300 K, B ～ 97 tesla). The energy-dependent widths arising from the relaxation processes with absorption and emission of a phonon show quite distinctive behaviors at low electron energies. At extreme low temperatures when few phonons are present, the width arising from the zero-point motion of the lattice is finite but very small. The charged-impurity scattering with the density as low as 10¹² cm^?3 numerically dominate the width due to the electron-phonon interaction below 10 K. The present theory supplements the previous work by Suzuki et al. where the elastic-scattering and high-temperature approximation were used.     

Temperature dependence of the spectral width in the intermediate valence compound CeAl3

We report measurements of the quasi-elastic spectral component of the compound CeAl₃ in the temperature range 60 mK < T < 125 K. At low temperatures, below ? 1 K, the quasi-elastic spectral width is effectively constant but increases as T^{$\text{1}\text{2}$} at higher temperatures. One possible interpretation of this behaviour is that it reflects the transformation of the f electrons from a Fermi liquid at low temperatures to a classical liquid at higher temperatures.     

Shallow Donors and Deep-Level Color Centers in Bulk AlN Crystals: EPR, ENDOR, ODMR and Optical Studies

The results of studies of shallow donors and deep-level color centers in bulk AlN crystals are presented. Two shallow donors (presumably oxygen located on the nitrogen site and carbon located on the aluminum site) are suggested to exhibit the DX-relaxation. Third shallow donor (presumably silicon on the Al site) shows the shallow donor behavior up to the room temperature and can be observed without light excitation at temperatures above 200 K. The values of the Bohr radius of the shallow donors are estimated. The structure of deep-level color centers (neutral nitrogen vacancy V _N) in bulk AlN crystals is determined and analyzed by electron paramagnetic resonance, electron-nuclear double resonance, optical absorption and thermoluminescence induced by X-ray irradiation. Spin-dependent recombination processes in AlN crystals are studied by means of optically detected magnetic resonance.