Direct conflict of Marcus theory with the law of conservation of energy

Marcus theory is a well‐known kinetic theory developed by Rudolph A. Marcus in 1956 for outer sphere electron transfer reactions according to the solvent polarization, which has been extensively used to describe the kinetics of various chemical reactions. However, when Marcus theory was examined with scientific principles, it is found that Marcus theory directly conflicts with the law of conservation of energy. Copyright © 2013 John Wiley & Sons, Ltd.     

Amplitude to phase conversion of InGaAs pin photo-diodes for femtosecond lasers microwave signal generation

When a photo-diode is illuminated by a pulse train from a femtosecond laser, it generates microwaves components at the harmonics of the repetition rate within its bandwidth. The phase of these components (relative to the optical pulse train) is known to be dependent on the optical energy per pulse. We present an experimental study of this dependence in InGaAs pin photo-diodes illuminated with ultra-short pulses generated by an Erbium-doped fiber based femtosecond laser. The energy to phase dependence is measured over a large range of impinging pulse energies near and above saturation for two typical detectors, commonly used in optical frequency metrology with femtosecond laser based optical frequency combs. When scanning the optical pulse energy, the coefficient which relates phase variations to energy variations is found to alternate between positive and negative values, with many (for high harmonics of the repetition rate) vanishing points. By operating the system near one of these vanishing points, the typical amplitude noise level of commercial-core fiber-based femtosecond lasers is sufficiently low to generate state-of-the-art ultra-low phase noise microwave signals, virtually immune to amplitude to phase conversion related noise.     

High-frequency properties of Fe/Cr superlattices with thin Cr layers in the millimeter-wavelength range

Microwave properties of Fe/Cr multilayer nanostructures with thin chromium layers (with thickness t _Cr < 1 nm) are analyzed. Experiments are performed by the method of penetration of microwaves in the frequency range from 26 to 38 GHz. The dependence of the transmission coefficient for microwaves on the constant magnetic field strength exhibits the microwave magnetoresistive effect and magnetic resonance. The resonance spectrum is reconstructed from measurements at various frequencies. The results of microwave measurements are analyzed together with the results of magnetic and magnetoresistive measurements.     

Analysis of the role of M-type hexaferrite-based materials in electromagnetic interference shielding

M-type hexaferrite has attracted much attention for its large magneto-crystalline anisotropic energy, exceptionally good chemical stability, corrosion resistance, high Curie temperature, and high coercivity. In this review paper, our goal is to examine the microwave absorption properties and related studies of M-type hexaferrite-based materials. The microwave absorption properties of hexaferrite-based materials in the S, X, and Ku-band are discussed with their corresponding reflection losses. Complementarity between magnetic loss and dielectric loss is found to have a great impact on the proper absorption of microwaves. The mechanisms corresponding to the microwave absorption in different morphologies and structural adaptations of hexaferrite have been elaborated in the article. The ongoing trends and future perspectives of these materials are also outlined.     

S波段长脉冲相对论返波振荡器实验研究

从物理机制上定性地分析了导致脉冲缩短的主要原因,给出了长脉冲重复频率运行下的相对论返波振荡器(RBWO)设计原则。结合传统谐振式返波振荡器的基本设计理论,设计和模拟优化了工作在S波段的长脉冲RBWO,并利用本实验室现有长脉冲脉冲功率驱动源开展了S波段长脉冲RBWO的实验研究。实验结果表明:在单次运行条件下,微波输出功率达到约2 GW、脉宽约90 ns;在10 Hz重复频率运行条件下,输出微波功率达到约1 GW、脉宽约100 ns。器件产生的微波频率为3.6 GHz,输出模式为TM01模,效率约20%。对实验结果分析表明,器件截止颈和第一个慢波结构结合处的爆炸发射是导致脉冲缩短的主要原因之一。     

Model of a microwave beam coupling to CO2 laser plasma

We have designed a transmission line model of the microwave coupling mechanism for a microwave pumped CO₂ laser. The model is a total loss ridge waveguide transmission line having nonuniform impedance. The laser plasma is modeled as a frequency-dependent lossy dielectric and acts as a distributed resistance in the length of the microwave cavity. The coupling structure of the microwaves is designed not to be resonant at the microwave source frequency of 2.45 GHz at 1 kW and propagating the total microwave field energy to be absorbed without internal reflection. An exact solution to this general transmission line propagation constant for a shunt resistance along length of the guide is found. The measurements and predictions of the parameters of the plasma conductivity as a function of the attenuation constant agree closely.     

Potential Advantages for Millimeter-Wave Heating of Powdered Metals

Based on electromagnetic induction heating, an interaction model of microwaves with powdered metal has been established. The formulae of attenuation coefficient, heating rate and heating conversion efficiency are obtained and analyzed. The results of calculations show that millimeter waves may be able to overcome the obstacle caused by smaller skin depth and have strong advantages for the microwave heating of powdered metals. Experiments are done for comparison with present theory.     

Experimental results from a tandem BWO-TWT system used to generatehigh-power microwaves

A relativistic backward wave oscillator (BWO) in tandem with a traveling wave tube (TWT) amplifier has been used to generate relatively long pulses of high-power X-band microwaves. In these experiments, a BWO is used to modulate the annular relativistic electron beam, which subsequently drives a TWT producing high-power microwave radiation. A special RF sever located between the two structures cuts off microwaves generated in the BWO from the TWT. Peak powers in excess of 100 MW are observed with overall beam-to-microwave efficiencies as high as 35%. By operating the BWO below saturation levels, pulse-shortening effects are minimized so that microwave pulses of duration comparable to that of the beam (100 ns) are possible. The operating frequency of the tandem system is tuned from 11 to 12 GHz by varying the effective energy of the beam     

2D Periodic Structure for Acoustic and Electromagnetic Radiation

The propagation of microwaves in the frequency range from 8.5 to 12GHz and acoustic radiation in the frequency range from 8.5 to 14 kHz in the same 2D periodic crystal formed by cylindrical spiral coils has been investigated. The frequency ranges in which the effective refractive index n_ef of the crystal is close to zero are found. In these ranges, microwaves are collimated and concentrated in a narrow lobe with an FWHM of about 9?. Focusing of divergent microwave and acoustic beams by a flat periodic structure has been observed in the frequency range where the effective refractive index of this structure is negative.     

Generation of acoustic waves by power microwave pulses with the use of thin metal films

We study the features of excitation of acoustic waves by high-power microwave pulses in thin metal films bordering on liquid. Aluminum films with thicknesses 1–10 nm deposited onto a quartz substrate were used in experiments. It is shown theoretically that the absorption coefficient of microwaves is maximum for film thickness from 2 to 3 nm and the value of this maximum is determined by the dielectric permittivity of the bordering liquid. Theoretical calculations and experiments are performed for water and ethyl alcohol. The sound generation in a layered system quartz-aluminum film-liquid is analyzed with the help of the step-by-step approach. At the first step, microwave energy is absorbed in the film and heat is released. Then heat almost instantly diffuses into a liquid whose thermal expansion creates an acoustic signal. Profiles of acoustic signals excited in aluminum films by microwave pulses with a 5-ns duration and an energy of up to 1 mJ are experimentally detected. The most efficient transduction was observed for an aluminum film 3.5 nm thick.     

微波大气击穿阈值的理论研究

本文通过对使用有效场强(或均方根场强)得到的微波大气击穿阈值表达式进行讨论, 指出其推导中所做的假设及这些假设应用到微波大气击穿过程中存在的问题. 然后分别使用解析理论和数值模拟对微波大气击穿过程中的有效电子温度变化过程和击穿阈值进行研究, 并将其与直流电场进行比较. 分析发现在高气压下, 电子能量转移频率高, 有效电子温度随电场大幅振荡, 由于电离频率随有效电子温度的增长率大于电子能量损失随有效电子温度的增长率, 因此在高气压时, 微波大气击穿阈值低于使用有效场强的击穿阈值. 通过大量分析, 给出了理论推导和数值模拟得到的微波大气击穿阈值拟合表达式.     

A Radially and Axially Extracted Virtual-Cathode Oscillator (Vircator)

Experiments are described in which a 5-? 1-MeV pulser drives virtual-cathode systems optimized to emit microwave radiation in the X band. Radiation is extracted both axially in TM modes and radially in TE modes. The threshold for microwave emission is found to be several times the space-charge limited current. The radiating frequency is approximately proportional to the electron beam plasma frequency with a proportional constant of (27?)1/2. Anode/cathode spacing is varied to demonstrate the frequency tunability of the virtual cathode as a microwave source. The radiation is broad band and frequency chirping is observed. Radiation patterns of the axially extracted radiation are described. The instantaneous efficiency of energy conversion from electrical to microwaves is ~2 percent. External excitation from an external source does not alter microwave generation.     

Diffusion-controlled processes among partially absorbing stationary sinks

A general linear response theory is presented to calculate the zero-wavevector and zero-frequency reaction rate coefficient for particles diffusing into absorbing spheres. Allowance is made for possible incomplete particle absorption. A Faxén-like theorem for chemical reactions is derived. The problem is solved completely for a simple regular array of sinks. Exact analytic expressions for the rate coefficient as a function of sink volume fraction are obtained for the sc and fcc lattices. The case of a disordered array of sinks is also considered and the leading order nonanalytic density dependence of the rate coefficient is calculated. In both cases an increase in the rate coefficient with sink density in a local region of the system is found. The general formalism is extended to examine the modification to the particle diffusion coefficient due to the presence of the spheres. For regular arrays of spheres, the mean field result is reproduced.Research supported in part by a grant from the National Research Council of Canada.     

New microwave system to determine the complex permittivity of small dielectric and semiconducting samples

This paper describes the new microwave bridge system with dielectric antennas of very small transverse dimensions (smaller than 10 mm) convenient for measurements of the complex dielectric permittivity of slab materials. The system enables (i) to measure by nondestructive way the complex permittivity of dielectric and semiconducting samples the dimensions of which are comparable or smaller than the wavelength of probing microwaves, (ii) to detect the material inhomogeneities. This system was verified at the frequency 37·5 GHz. In this paper measurements of the resistivity of the Si samples are given. Results obtained are in good agreement with the theory.     

A new reactor for process intensification involving the simultaneous application of adjustable ultrasound and microwave radiation

Ultrasound (US) and Microwaves (MW) are effective methods for processes intensification. Their combined use in the same reactor can lead to remarkable results. Recently there has been a resurgence of interest in this field for new synthetic applications using reactors based upon existing technologies. We describe here a new type of apparatus in which the thermal energy is continuously removed from the system making possible the use of high power and adjustable ultrasonic and microwave densities throughout the process. The installation consists of a glass reactor located in a monomode applicator which is immersed at the same time in an ultrasonic device which can be operated at different frequencies and powers. A liquid, transparent to microwaves, was used to couple ultrasonic energy to the reactor and to remove the heat generated. Comsol software was used to get information about the distribution of ultrasonic and microwave energy between the reactor liquid and the coupling fluid. The performance was assessed using the conversion of p-nitrophenol into 4-nitrocatechol as a chemical dosimeter and a transesterification.     

X波段新型低阻抗高功率微波源的模拟研究

提出了一种新型低阻抗高功率微波源,能在单个器件内产生两束锁相的相干高功率微波,对两束相干微波进行功率合成有望在单个高功率微波器件中实现更高的功率输出.粒子模拟结果显示,在电压687 k V、磁场0.8 T时,该微波源整体阻抗36?,两束微波的频率都为9.72 GHz,输出功率分别为1.20 GW和2.58 GW,功率效率分别为28%和30%;两束输出微波之间频率抖动小于±3 MHz,相位差抖动小于±3?.     

Dielectric polarization in the Planck theory of sonoluminescence

Sonoluminescence observed in the cavitation of liquid H2O may be explained by the Planck theory of SL, which treats the bubbles as collapsing miniature masers having optical waves standing in resonance with the dimensions of the bubble cavity. Microwaves are shown to be created from the Planck energy of the standing waves, provided the bubble wall can be treated as a perfect blackbody surface. Liquid H2O is strongly absorbent in the ultraviolet and there the bubble approaches a Planck blackbody enclosure. The microwaves are created at frequencies proportional to the bubble collapse velocity only to be promptly absorbed by the rotation quantum states of the H2O and other bubble wall molecules. The microwaves are absorbed discretely at rotation line frequencies, or continuously by dipole rotation at frequencies from 1 to 30 GHz. In the liquid state, molecular rotation of the H2O molecule is hindered and the microwave energy is rapidly turned into bending energy by intermolecular collisions. Subsequently, the bubble wall molecules may thereby ionize and produce visible photons. The microwaves create intense electrical fields in the bubble wall by dielectric polarization. If the gases adjacent to the bubble wall undergo electrical breakdown, free electrons are created, thereby providing sonoluminescence with a magnetic field effect.     

Mechanism and properties of thermally biological effect of Micro waves

水在生命体中是大量存在的,它是维持生命的必要物质.它能促进细胞的繁殖和血液的循环,促进和参与生物化学反应,为生物大分子的功能发挥提供适当条件.由于它是具有一定偶极矩的微观小分子,其转动频率是处在微波范围内,所以我们判定生物体中的液态水能吸收一定频率和强度的微波,并可以将所吸收的微波能量转化为水分子无规运动的热能,使水温升高.我们的实验结果应证了这个机制,从而可导致血液循环,细胞繁殖和一些生化反应的加快和增强DNA,蛋白质和酶的生物活性等生物功能.这就是毫米波的生物热效应的机理和特性.     

Unusual microwave response of dirac quasiparticles in graphene

Recent experiments have proven that the quasiparticles in graphene obey a Dirac equation. Here we show that microwaves are an excellent probe of their unusual dynamics. When the chemical potential is small, the intraband response can exhibit a cusp around zero frequency Omega and this unusual line shape changes to Drude-like by increasing the chemical potential |mu|, with width linear in mu. The interband contribution at T=0 is a constant independent of Omega with a lower cutoff at 2mu. Distinctly different behavior occurs if interaction-induced phenomena in graphene cause an opening of a gap Delta. At a large magnetic field B, the diagonal and Hall conductivities at small Omega become independent of B but remain nonzero and show a structure associated with the lowest Landau level. This occurs because in the Dirac theory the energy of this level, E0 = +/-Delta, is field independent in sharp contrast to the conventional case.     

矩形孔缝耦合特性实验研究

 对矩形孔缝在微波频率为2～18GHz范围内的耦合系数进行了实验研究；建立了实验方法和实验装置。实验结果表明：对于矩形孔缝，当入射电场方向垂直于孔缝长边时，在微波波长约等于2倍孔缝长度时，发生共振效应，在该频率附近一定带宽内耦合系数最大，并且在共振频率处存在着场增强效应。