A STUDY ON ABSORPTION OF Na ATOMS ON Si(100) 2×1 SURFACES WITH DV-Xα METHOD

The Na absorption on Si(100) 2×1 surface is studied with quantum chemistry molecular cluster method. The calculated results show that the most favourable absorption site of Na is the cave site and the charge transfer of Na atom to Si is large when the Na coverage is smaller than 0.5 monolayer (ML). A Na chain is formed along the cave sites at the 0.5 ML Na coverage, the charge transfer then becomes small. The calculated density of states show that the Na atoms are metallic along the chain. At 1 ML coverage, the Na atoms occupy both the cave and pedestal sites and form a double-layer. There is a charge transfer of 0.5e from each Na atom to the Si surface. The calculated surface energy shows that the saturation absorption of Na on Si surface is 1 ML.     

碰撞诱导钠分子A1Σ+u→X1Σ+g的荧光光谱

用532.0 nm激光激发Na2分子到B1Πu电子态,记录了Na(3P)原子的跃迁和Na2分子的A1Σ+u-Χ1Σ+g的谱带.由Na与Na2激发态发射的光谱及其强度可以认定在Na-Na2系统中的碰撞过程,Na(3P)原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线.而A1Σ+u-Χ1Σ+g谱带是由B1Πu到21Σ+g的碰撞转移后再由21Σ+g到A1Σ+u的辐射而引起的.在360℃,根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ+g)碰撞转移率系数为7.1×10-10 cm3s-1,而B1Πu的预解离率为2.3×106 s-1.     

钠分子B^1∏u与2^1∑g^＋间的碰撞激发转移

The B 1pi(u) electronic state of Na2 was excited by the 441.6 nm He-Cd laser line. The Na atomic transitions and the A 1sigma(u)+ --> X 1sigma(g)+ band of Na2 were recorded. From the intensities and spectra of the Na and Na2 fluorescence several collisional processes in the excited sodium atom-dimer system were identified. The Na atomic lines are the result of collisional energy transfer from Na2 (B 1pi(u)) to Na(3P). Predissociation process may also contribute to atomic fluorescence. The A 1sigma(u)+ --> X 1sigma(g)+ band is interpreted through a populating mechanism involving collisional transfer from B 1pi(u) to 2 1sigma(g)+ followed by a radiative transfer to the A 1sigma(u)+ state. From the decay constants and fluorescence intensities, the rate coefficient at 360 degrees C for collisional energy transfer from Na2 (B 1pi(u)) to Na2 (2 1sigma(g)+) was found to be 5.7 x 10(-10) cm3 x s(-1). The predissociation rate of the B 1pi(u) is 2.7 x 10(6) s(-1).     

碲材料中钠,钾杂质成份的测定

本文揭示了钠、钾受基体元素碲干扰的现象和分析系统中酸度对钠、钾吸光度的影响,在理论上探讨了碲对钠、钾干扰的原因,利用加入盐酸和铝元素的方法分别排除碲对钾、钠的干扰,提出一个方便,实用的测定方法,回收率和RSD分别为95-102%和7.4%。     

A STUDY ON ABSORPTION OF Na ATOMS ON Si(100) 2×1 SURFACES WITH DV-Xα METHOD

The Na absorption on Si(100) 2×1 surface is studied with quantum chemistry molecular cluster method. The calculated results show that the most favourable absorption site of Na is the cave site and the charge transfer of Na atom to Si is large when the Na coverage is smaller than 0.5 monolayer (ML). A Na chain is formed along the cave sites at the 0.5 ML Na coverage, the charge transfer then becomes small. The calculated density of states show that the Na atoms are metallic along the chain. At 1 ML coverage, the Na atoms occupy both the cave and pedestal sites and form a double-layer. There is a charge transfer of 0.5e from each Na atom to the Si surface. The calculated surface energy shows that the saturation absorption of Na on Si surface is 1 ML.     

ICP-AES测定野生羌活药材中K、Na和Al

利用电感耦合等离子体-原子发射光谱法（ICP-AES）测定不同采收时间（5、6、7、8月和9月）野生羌活药材中K、Na、Al 3种金属元素的含量,应用SPSS16.0分析软件对结果进行统计分析。研究结果表明,5—9月野生羌活药材中均以K元素含量最高;K和Na、Na和Al的含量呈负相关,K和Al的含量呈正相关;K元素的含量在5月到6月增加,6月到8月呈下降趋势,8月到9月急剧升高;Na元素的含量呈先上升（5—6月）后下降（6—9月）的趋势;Al元素的含量呈先降低（5—6月）再升高（6—9月）的趋势。     

硅酸盐玻璃中的Na,Mg K-边XANES谱研究

本文利用同步辐射的NaK 边X 射线近边结构 (XANES)谱研究了含Na玻璃 (Na2 O SiO2 P2 O5和Na2 O SiO2 )的NaK 边的特征 ,同时建立了含磷 (P)的钠玻璃中NaK 边的能量 ,其能量位置随着P的含量增加 ,而增大其能量位置。CaMgSi2 O6(Di) NaAlSi3 O8(Ab)玻璃中MgK 边XANES的能量和Mg—O的键长有关系。在Di Ab玻璃中的Mg—O键距是 2± 0 0 4 。表明本方法可以作为研究含Mg玻璃的配位与局部结构新方法     

On the temperature dependence of Na migration in thin SiO2 films during ToF-SIMS O2 depth profiling

The detection of Na in insulating samples by means of time of flight-secondary ion mass spectrometry (ToF-SIMS) depth profiling has always been a challenge. In particular the use of O₂⁺ as sputter species causes a severe artifact in the Na depth distribution due to Na migration under the influence of an internal electrical filed. In this paper we address the influence of the sample temperature on this artifact. It is shown that the transport of Na is a dynamic process in concordance with the proceeding sputter front. Low temperatures mitigated the migration process by reducing the Na mobility in the target. In the course of this work two sample types have been investigated: (i) A Na doped PMMA layer, deposited on a thin SiO₂ film. Here, the incorporation behavior of Na into SiO₂ during depth profiling is demonstrated. (ii) Na implanted into a thin SiO₂ film. By this sample type the migration behavior could be examined when defects, originating from the implantation process, are present in the SiO₂ target. In addition, we propose an approach for the evaluation of an implanted Na profile, which is unaffected by the migration process.     

Absolute quantification of Na+ bound fraction by double-quantum filtered 23Na NMR spectroscopy

A method is described for the absolute quantification of double-quantum filtered spectra of spin-3/2 nuclei ((23)Na). The method was tested on a model system, a cationic exchange resin for which the number of Na(+) binding sites was quantitatively controlled. The theoretical and experimental approaches were validated on samples with different Na(+) concentrations. An excellent agreement between the results obtained by double-quantum and single-quantum acquisitions was found. This method paves the way for absolute quantification of both bound and free fractions of Na(+), which are determining factors in the characterization of salted/brined/dried food products.     

Optical polarization of 24Na nuclei in a trap based on photoinduced drift

The results of experiments on the polarization of nuclei of the 24 Na radioactive isotope in a gas trap are presented. The action of the trap is based on the effect of the photoinduced drift of atoms caused by laser radiation. The anisotropy of γ-radiation emitted by ²⁴Na during the illumination of sodium vapor in the trap by circularly polarized laser radiation is measured and its dependence on the temperature of the trap walls is analyzed. A degree of polarization of ²⁴Na nuclei of 62 ± 2% is attained at temperatures above 1300 K, for which a rapid desorption of Na atoms from the walls and the decomposition of Na-based compounds take place.     

Strongly enhanced magnetic moments of vanadium impurities in thin films of sodium and potassium

Thin quench-condensed films of Na and K are covered with 1/100 of a monolayer of V. Then the impurities are covered with several atomic layers of the host. The magnetization of the films is measured by means of the anomalous Hall effect. For V impurities on the surface of Na and K, a magnetic moment of 7 Bohr magnetons is observed. After coverage with the host, the V moment became 6.5 mu(B) for the Na host. These results contradict the favored atomic model (predicting 3/5 mu(B)) and the resonance model. A polarization of the alkali host appears to be the only resolution.     

Anomalous conductivity effects in (Na,K) mixed crystals of the β-Al2O3 type

Anomalous behavior has been observed in the ionic conductivity of (Na,K) mixed crystals of the alkali gallates and aluminate of the β-Al₂O₃ type fast ion conductors. The conductivity goes through a minimum at some intermediate composition as a consequence of a maximum in the activation energy, and is most pronounced in the (Na,K)-β-gallate, followed by (Na,K)-β-Al₂O₃ and (Na,K)-β“-gallate. The effect is similar to the well-known “mixed alkali effect” in glasses. A second anomaly consisting of a pronounced increase in conductivity over about a 70° temperature range, without any permanent change in activation energy, was observed for some compositions of (Na,K)-β“-gallate.     

不同海水浓度灌溉菊芋的营养元素测定

利用原子吸收分光光度法分析了不同海水浓度灌溉不同年份采摘的菊芋中多种微量元素的含量。方法灵敏度高,精密度好,相关系数(r)在0.997 1～0.999 7之间。实验中比较其差异性,结果表明：菊芋是典型的高钾低钠食品,其含量K＞Mg＞Na＞Fe＞Ni＞Zn＞Cu＞Mn＞Cd,Pb,Cr含量极少。不同年份和不同海水浓度对其有一定的影响。此法有一定应用价值。     

23 Na磁共振成像的初步实验研究

介绍了用于²³Na磁共振成像实验的收发一体表面线圈的设计、制作原理与实际制作. 用制作的²³Na表面线圈在Bruker Biospec 47/30磁共振成像仪上采集了不同浓度NaCl溶液,盐腌制鹌鹑蛋和大鼠头部的²³Na密度像,为深入开展23Na磁共振成像的生物医学应用研究奠定基础.     

Controlling Population Transfer and Dissociation Rate of Na2 Molecules with Ultra-Short Intense Laser Pulses

A scheme used for controlling the population transfer and the dissociation rate of Na2 molecules is described by using the quantum wavepacket dynamical method. It is theoretically shown that the population transfer and the dissociation rate of Na2 molecules can be controlled by pump and probe laser pulses with appropriate widths of pulses, sequence and intensities.     

Na-doped optical Germanium bulk crystals

In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 10¹⁵ cm^?3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5?10¹³ to 4?10¹⁴ cm^?3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.     

Cs(8D,9D)+Na(3S)碰撞激发转移过程

此文报道异核Cs(8D,9D)+Na(3S)→Cs(6P)+Na(3P)的碰撞能量转移过程.两步激发Cs原子到9D3/2(8D3/2)态.应用双调制技术探测Na(3PJ)原子发射的荧光,基态Na原子密度用光学吸收方法测量.得到了REP率系数,讨论了其它过程对率系数的影响.     

氦喷嘴激光离子源离线系统的实验结果

简要介绍了建立在清华大学的氦喷嘴激光离子源离线系统.并给出了在氦喷嘴出口处激光直接共振电离喷束中的钠原子的实验结果.此结果表明,在氦喷嘴出口处,用激光在束电离钠原子是可行的.由此出发可设计具有Z选择性、效率高、可测同位素寿命下限低又能适用于高温难熔元素的激光离子源.     

若干钠锗酸盐晶体和熔体的温致结构变化及其锗配位数的拉曼光谱研究

本文测定了Na4GeO4、Na2GeO3、Na2Ge4O9和Na4Ge9O20等晶体从273K到1413K升温及熔体的拉曼光谱,结合分析金红石型GeO2的相关结构和光谱,研究了其微结构单元在升温过程中的变化、熔体中的形态和锗的氧配位数及其温致变化。Na4GeO4和Na2GeO3晶体结构单元为GeO4四面体,在升温过程及其熔体中锗维持四配位。Na2Ge4O9和Na4Ge9O20晶体结构单元为GeO4四面体和GeO6八面体共存,升温过程中,GeO6八面体将发生结构转变,在熔融状态全部转变为GeO4四面体,并产生与钠离子等摩尔分数的非桥氧,在熔体中锗的氧配位数为4。研究还表明,桥氧的对称弯曲振动模可以反映不同微结构单元间的连接,并且随着温致结构的变化而产生特征性的变化。     

Luminescence in ZnSe with Na and Al doping

Photoluminescence of ZnSe doped with Na and Al has been studied. A broad band in the blue region of the spectrum has been observed at temperatures below 150 °K. This band is apparently due to donor-acceptor pair transitions involving Al donors and Na acceptors. Temperature dependence of the luminescence indicates that the Na-acceptor level is relatively shallow.