Magnetic field effect on highly excited states near ionization potential of nitric oxide

Fluorescence excitation spectra due to the A ²∑–X ²Π transition of gaseous nitric oxide (NO) were measured in magnetic fields, H; ranging from 0 ≤ H ≤ 10 T. Lines in the observed spectra were assigned by using quantum mechanical calculations. Based on the assignment, two-color resonance-enhanced multiphoton ionization spectra via a single Zeeman sublevel in the A state were measured to observe the effect of magnetic fields on electronic states near the ionization potential (IP). Complicated structures due to strong n- and l-mixing in highly excited Rydberg states were observed below the IP. It was found that new resonance appears above the IP for H ≤ 4T. By using a semi-classical calculation, this resonance was assigned to the quasi-Landau resonance, which was observed for the first time in molecules.

© 2003 Elsevier Ltd. All rights reserved.     

Associative ionization involving highly excited alkali metal atoms

Papers on collisional ionization of excited alkali metal atoms by atoms in their ground states are briefly analyzed. The main premises behind the theoretical models of the process and some experimental findings for a number of atoms during the optical excitation of an effusive atomic beam are described.Latvian University, Riga. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 5, pp. 655–657, May, 1992.     

Magnetic field intensity in near field zone of loop antenna for RFID systems

The structure of a loop antenna of electrically large diameter with the loop perimeter split by capacitors in the form of planar two-wire (PTW) lines is considered. The antenna characteristics are calculated for one- and two-sided arrangement of the PTW lines and the obtained data are compared to the results of measurements. It is shown that the arrangement of PTW lines significantly influences the distribution of current over the loop perimeter.     

Magnetic field effect on electron emission from plasma

The influence of external magnetic field on the significant parameters of electrons from laser induced plasma (LIP) is investigated. A Q-switched Nd:YAG laser (1064 nm, 9-14 ns, 10 mJ, 1.1 MW) is focused on annealed, 4N pure (99.99%) Silver target (2 × 2 × 0.2 cm³) for production of plasma under vacuum ∼10⁻³ torr. Temperature, density and energy measurements for electrons were made by self fabricated Langmuir probe both in the absence and presence of external magnetic field (∼1.2 T) at different positions. The signals are recorded on 200 MHz UTT 2202 digital storage oscilloscope. The results thus obtained reveal decrease in electron temperature, energy and density in presence of external magnetic field. Confinement of plasma is also observed.     

近场条件下视觉距离感知对响度的影响

文章研究了近场条件下,当声源距离改变时,视觉距离感知对响度的影响。在消声室中,使用球形声源在试听者的正前方发声。8位试听者分别在睁眼和闭眼的条件下,对3种中心频率(500 Hz、1 kHz和2 kHz)、8个距离(0.3～1.0 m,1.0 m为参考距离)的声信号进行了响度匹配。结果显示,随着声源距离的减小,睁眼时响度增加得要比闭眼时少一些。而闭眼时的响度匹配结果与封闭耳道口声压级的变化情况相一致。这说明闭眼时试听者根据耳道口的声压级来判断响度,而睁眼时视觉距离信息会对响度产生影响。结果还显示,对于频率越低的声信号,视觉距离感知造成的影响越大。     

Magnetic Aharonov-Bohm effect under time-dependent vector potential

A probability distribution for the scintillations caused by electrons hitting a screen after diffraction on a wire is calculated for the case when time-dependent vector potential is applied in the path of electron travel. Negative experimental results are explained and proper conditions for future experiments are proposed using the expression obtained.     

Magnetic shape memory effect and highly mobile twin boundaries

Abstract

The magnetic shape memory effect can be classified as an example of the multiferroic effect combining ferro-elasticity and (ferro)magnetism. After short overview of all known effects the focus is on magnetic field induced structure reorientation (MIR) in the martensite of Ni–Mn–Ga. In this material giant deformations of up to 12% have been observed in moderate magnetic fields. The phenomenology of the effect is first discussed and a model presented. The properties of Ni–Mn–Ga relevant to MIR are then considered. One necessary condition for MIR is a highly mobile twin boundary or interface between two differently oriented martensite variants (ferroelastic domains). In 10M modulated martensite, two types of mobile twin boundary (type I and type II) are observed with complex layered microstructures consisting of a hierarchy of twinning systems. The boundaries strongly differ according to the magnitude and temperature dependence of the twinning stress. Finally, the nature of these boundaries and their different behaviour is reviewed.     

Vacuum field correlations and three-body Casimir–Polder potential with one excited atom

The three-body Casimir–Polder potential between one excited and two ground-state atoms is evaluated. A physical model based on the dressed field correlations of vacuum fluctuations is used, generalizing a model previously introduced for three ground-state atoms. Although the three-body potential with one excited atom is already known in the literature, our model gives new insights on the nature of non-additive Casimir–Polder forces with one or more excited atoms.     

Magnetic field enhances the graphitized structure and field emission effect of carbon nanotubes

This study uses a low temperature thermal chemical vapor deposition with an applied external magnetic field to grow carbon nanotubes (CNTs) on Ni/Ag-printed glass substrates. A mixture of C₂H₂ and H₂ gas was used for the growth of the CNTs. A Ni catalyst layer was deposited on the Ag-printed glass substrate by pulse electroplating. Scanning electron micrographs as well as the presence of two sharp peaks at 1320 cm⁻¹ (D band) and 1590 cm⁻¹ (G band) in the Raman spectra indicate that the graphitized structure of CNTs synthesized under a magnetic field has higher quality (i.e., a D-band to G-band intensity ratio of 0.303) than CNTs synthesized without a magnetic field. Transmission electron micrographs show a fine Ni catalyst at the tip of the tube for CNTs synthesized under a magnetic field, exhibiting a CNT “tip-growth” model. The synthesis of CNTs in the presence of a magnetic field also generates better field emission properties and better lighting morphology than without a magnetic field.     

Classification and supermultiplet structure of doubly excited states

Based upon the analysis of electron correlations in hyperspherical coordinates for two-electron atoms for arbitrary L, S and π states, a classification scheme for all doubly excited states is presented. A new set of correlation quantum numbers K, T and A, is introduced. Here (K, T) describes wave functions in hyperspherical coordinates, it is shown that states with identical (K, T)^A have isomorphic correlations. This isomorphism is shown to be the origin of the supermultiplet structure of doubly excited states.     

Ageing and field effect studies on discontinuous silver films at near liquid nitrogen temperatures

The post deposition resistance changes in discontinuous silver films deposited in a vacuum of 2 × 10^–6 torr on glass substrates maintained at near liquid nitrogen temperatures have been studied. Reduced agglomeration rates in comparison with films studied at room temperature were obtained, supporting the thermally assisted mobility coalescence model explaining the post deposition resistance increase. The non-linearI-V characteristics of one of the films followed by observations of resistance changes before and after field effect measurements on the other films have been explained as arising due to field-induced structural changes. The investigations of the variation of film resistance with temperature revealed a transition temperature. A fall in resistance with increasing temperature below the transition temperature has been explained by an increase in the number of thermally charged islands. The increase in resistance with temperature above the transition temperature is due to an increase in the thermally assisted mobility coalescence.     

室温磁致冷最新进展

在回顾了磁致冷工质发展进程的基础上，介绍了室温磁致冷工质研究中具有突破性的最新进展。指出类钙钛矿化合物作为室温磁致冷工质具有很好的应用前景。     

Upper critical field and isotope effect in the oxide superconductors

In a model for which the pairing is due mainly to an electronic mechanism supplemented by a small phonon contribution, we study the isotope effect exhibited by the upper critical magnetic field H _c2 and compare with the critical temperature. When paramagnetic impurities are added, we find very different behaviours from that predicted in a pure phonon model. The alignment of the paramagnetic spin by the external magnetic field as well as Pauli limiting is neglected in our calculations.     

The effect of electric field on nonpolar liquids not contacting with potential electrodes

It is experimentally established that a contactless exposure of liquids representing the homologous series of alkanes to a high-strength electric field leads to the appearance of an optical anisotropy. The effect, related to a field-induced partial ordering (orientation) of extended molecules, is more clearly manifested in the liquids possessing higher molecular masses (longer molecules).     

Simultaneous velocity and temperature measurements in gaseous flowfields using the vibrationally excited nitric oxide monitoring technique: a comprehensive study

The performance of the vibrationally excited nitric oxide monitoring (VENOM) technique for simultaneous velocity and temperature measurements in gaseous flowfields is presented. Two different schemes were investigated, employing different methods to "write" a transient NO grid in the flow using the 355 nm photolysis of NO(2), which was subsequently probed by planar laser induced fluorescence imaging to extract velocity maps. We find that only one scheme provides full-frame temperature maps. The most accurate velocity measurement was attained by writing an NO pattern in the flow using a microlens array and then comparing the line displacement with respect to a reference image. The demonstrated uncertainty of this approach was 1.0%, corresponding to 7 m/s in a 705 m/s uniform flow. We found that the uncertainty associated with the instantaneous temperature measurements using the NO two-line thermometry technique was largely determined by the shot-to-shot power fluctuations of the probe lasers and, for the flows employed, were determined to range from 6% to 7% of the mean freestream temperature. Finally, simultaneous and local velocity/temperature measurements were performed in the wake of a cylinder in a uniform Mach 4.6 flowfield. The mean and fluctuation velocity and temperature maps were computed from 5000 single-shot measurements. The wake temperature and velocity fluctuations, with respect to the freestream values, were 15% to 30% and 5% to 20%, respectively. The spatial distributions agree with the results of computational fluid dynamics (CFD) simulations. Our results suggest that the VENOM technique holds promise for interrogating high-speed unsteady flowfields.     

二甲基硅酮的分子激发态和离解产物

用SAC-CI/6-311g方法计算了二甲基硅酮[DMS,(CH3)2SiO]的单重态和其激发态,得到基态为X1A1,其3个低激发态依次为1A2、1A1和1B1,其电子光谱都出现在紫外可见区,这是二甲基硅酮(DMS)的独特之点.根据群的对称性原理,指出在二甲基硅酮[DMS,(CH3)2SiO]中(图1),同时离解5H和8H,是对称性最许可的.计算出同时离解3C-5H和4C-8H时的离解能和同时离解键1Si-3CH3和1Si-4CH3时的离解能,由基H和CH3会发生自由基反应,这与脉冲辐射的紫外可见光谱无结构[3]的实验相合.可以预计在离解气体产物中,甲烷CH4成分最多,其次为H2,乙烷C2H6最少,文献[1]的实验正是如此.     

The effect of magnetic field on domain electroluminescence in barium titanate crystals near the ferroelectric phase transition

By measuring electroluminescence (EL) in barium titanate crystals exposed to a pulsed electric field in combination with a magnetic field, we have studied the dependence of a shift in the temperature of maximum EL on the magnetic field strength and on the mutual orientation of the electric and magnetic fields. The possible mechanisms of the observed effects are discussed.     

Surface ionization properties of alkali metal oxide bronze

The process of selective ionization of a nitro compound (trinitrotoluene) on the surface of poly- and single-crystalline samples of sodium-vanadium oxide bronze has been studied in air at atmospheric pressure.     

Magnetic field sensor based on compensated silicon

The phenomenon of negative magnetoresistance in compensated silicon doped with manganese has been studied. The possibility of using this effect in magnetic field sensors is assessed.