Parameters of the Water Vapor Line Contour at Helium Broadening

Optics and Spectroscopy - The method of medium frequencies has been applied to calculate the collisional half-widths of vibrational-rotational lines of a water molecule under helium pressure. The...     

红外光谱差减技术扣除水汽吸收干扰的局限性

红外光谱差减技术在扣除背景组份干扰方面得到广泛应用,但其扣除空气中水汽效果却不尽如人意。研究了不同湿度的水汽光谱与光谱差减效果的关系,以探究光谱差减技术在水汽扣除领域局限性的原因。结果表明：(1)相对湿度改变,水汽的红外光谱也发生变化,不管如何小心地选择比例系数f,从相对湿度x%的水汽光谱A_x,也不能完全扣除相对湿度为y%的水汽光谱A_y,即fA_x≠A_y。(2)相对湿度改变,水分子团簇(H₂O)_n的相对组成也会发生变化,这是导致光谱差减技术局限性的主要原因。(3)将湿度为x%和y%的两水汽光谱A_x和A_y进行线性组合,则可以高度近似地模拟出介于两者之间的湿度的水汽光谱。比如用40%水汽谱和30%水汽谱,可以模拟得到32%或35%或37%的水汽谱。实验结果表明这是扣除水汽干扰效果更好的路径。(4)论证了水汽补偿湿度滴定法具有高效性的原因。     

空气介质阻挡放电不同放电模式的光谱特性

采用光谱方法,研究了空气介质阻挡放电中流光向类辉光转变时电子能量的变化。利用氮分子第二正带系(C3Π_u→B3Π_g)的发射谱线,测量了氮分子(C3Π_u)的振动温度。通过考察氮分子离子391.4 nm谱线强度与氮分子337.1 nm谱线强度之比,研究了电子平均能量的变化。结果表明,流光向类辉光转变时,氮分子(C3Π_u)的振动温度激增,氮分子离子391.4 nm相对谱线强度突增,表明类辉光放电模式中电子能量比流光放电模式中电子能量高很多。实验还发现,气隙间距不同,这两种放电模式转变所对应的转变气压不同,但转变气压与气隙间距的乘积值保持不变。     

The Polarization Response Function and the Dielectric Permittivity of a Plasma

We give a simple direct derivation of the polarization response function h for linear electrostatic excitations of a plasma (without magnetic field) considering the effect of a percussion on the electrons. The physical meaning of the procedure is discussed, thus bringing into light basic facts of the plasma dielectric behavior. The result h = ?p2f0(x/t) (where f0 is the electron distribution function in velocity space and ?p the plasma frequency) is obtained without passing through the Vlasov-Poisson equations as in the standard theory. We show that the equivalence between the present method and the classic Landau analysis rests on properties of the Fourier transform applied on velocity space.     

Dependence of the Real Part of the Dielectric Permittivity of Freshwater Ice on the Temperature and Storage Time in the Centimeter Wave Range

Using a resonator at frequencies 6.1–6.4 GHz, we measure the real part of the dielectric permittivity of newly formed freshwater ice with different content of impurities. We study the dependence of this quantity on the temperature in the range from -10°C to -90°C as well as its temporal variation for an ice storage time of up to three weeks at a constant temperature. It is found that the dependence of the dielectric permittivity of newly formed ice on the temperature in the studied range can be represented as two straight lines with a kink in the vicinity of -30°C. For an ice storage time of up to three weeks, a significant change in the slope of this dependence at higher temperatures and the disappearance of the kink are observed. The possible mechanism of this phenomenon is related to the existence and metamorphism of liquid conducting water films.     

不同微场分布函数下的光谱线型

根据光谱学,总的光谱线型是各种加宽机制的卷积结果。考虑到等离子体中的离子碰撞,Stark加宽本质上是一种非对称的光谱线型, 其中微场分布函数对光谱线型起着非常关键的作用。该文利用不同的微场分布函数研究了微场分布函数对总的光谱线型的影响。研究结果表明,在电子加宽参数和离子加宽参数很小时,不同微场分布函数对整个光谱线型的影响基本相似,但随着离子加宽参数的增加,3种不同的微场分布函数对Stark光谱线型的影响逐渐增加; 随着电子加宽参数的增加,不同的微场分布函数对Stark光谱线型的影响也逐渐增加; 但总体上Holtsmark分布和Nearest-Neighbor场分布下的光谱线型差别较小,但是Mayer模型对光谱线型影响较大。特别是,当离子加宽参数较大时,Mayer模型对光谱线型的影响异常明显,这也正说明离子间碰撞剧烈时对光谱线型的影响很大。该结果对等离子体参数诊断有一定参考价值。     

Coupling of NRD-Guide Filled with Low Permittivity Dielectric Between Waveguides

A new version of NRD-guide coupling structure is proposed in which a low permittivity dielectric is filled between the coupling waveguides. It takes full advantage of the common NRD-guide with more flexibility. The choice of different dielectric materials can optimize the required performance. The corresponding coupling characteristics are analyzed. Some examples are given to show the new coupling characteristics. An important feature is the enhanced coupling between the waveguides and increased attenuation in the transverse direction, and this implies a size reduction and enhanced EMC capability. Furthermore, the filling of the low dielectric material between the coupling waveguides makes the structure an integrated unit and especially suitable for realization by micro-electromechanical system (MEMS) or by microwave integrated circuits.     

介质阻挡放电中体放电和沿面放电的光谱线形研究

在放电间隙较大的介质阻挡放电中,利用高速照相机,同时观察到了体放电(VD)和沿面放电(SD)。采用光谱法,研究了VD和SD的光谱线形随放电参数的变化。在氩气介质阻挡放电中,测量了VD和SD的Ar Ⅰ(2P₂→1S₅)谱线展宽和频移随气压及放电间隙的变化。结果发现：SD的展宽和频移均比VD的大,说明SD的电子密度高于VD的电子密度;随着压强从40 kPa增大到60 kPa,VD和SD的谱线展宽及频移均增加,表明它们的电子密度均随压强的增大而升高;随着d值从3.8 mm增大到4.4 mm,VD和SD的谱线展宽也增加,反映它们的电子密度均随d值的增大而增加。     

Weak Line Water Vapor Spectrum in the 11 787-13 554 cm Region

Long-pathlength Fourier transform spectra of water vapor recorded previously by Schermaul et al. (J. Mole. Spectrosc.211, 169 (2002)) are analyzed in the range 11 787-13 554 cm⁻¹. Wavenumbers, absolute intensities, and self-broadening coefficients, with associated uncertainties, are presented for 2137 lines. Analysis of these lines using variational linelists has been conducted leading to the assignment of 1906 of the new lines to 23 different upper vibrational states in the 3ν+δ, 4ν, and 4ν+δ polyads, a further 19 lines are ascribed to H₂¹⁸O. Comparisons are made with the HITRAN database.     

Weak Line Water Vapor Spectra in the Region 13 200-15 000 cm

New Fourier transform spectra of water vapor are presented in the range 6500-16 400 cm⁻¹ obtained using pathlengths of up to 800 m and long integration times. These spectra have a significantly higher signal-to-noise than previous measurements in this wavenumber range. Wavenumbers, absolute intensities and self-broadening coefficients, all with associated uncertainties, are presented for 3604 lines in the region 13 200-15 000 cm⁻¹. Analysis of these lines using variational linelists, along with other unassigned lines from previous studies, has been conducted. This leads to 952 new line assignments to transitions involving 35 different vibrational states of H₂¹⁶O. A smaller number of lines are assigned to H₂¹⁸O and H₂¹⁷O.     

不同微场分布函数对Stark线型的影响

利用不同的微场分布函数研究了其对Stark加宽光谱线型的影响.根据Stark加宽理论,考虑到等离子体中的离子碰撞,Stark加宽本质上是一种非对称的光谱线型,其中微场分布函数对光谱线型起着非常关键的作用.研究结果表明,总体上Holtsmark分布和Nearest-Neighbor场分布下的Stark光谱线型差别不太大,但是Mayer模型对Stark加宽光谱线型影响较大.并且随着离子加宽参数的减小,三种不同的微场分布函数对Stark光谱线型的影响逐渐减小;随着电子加宽参数的减小,不同的微场分布函数对Stark光谱线型的影响也逐渐减小;同时发现,当离子加宽参数减小到一定程度时,不同微场分布函数对整个光谱线型的影响基本相似,这也正说明离子间碰撞剧烈时对光谱线型的影响很大.     

温度和压强的变化对谱线线型峰值的影响

谱线线型是用于气体浓度测量中的一个重要参数。本文基于温度(压强)变化会引起相应压强(温度)的变化这一点,考虑温度和压强同时变化对气体线型峰值的影响。通过分析氟化氢的吸收谱线,发现可用Lorentzian线型来计算峰值吸收系数的温度和压强范围都扩大,而Gaussian线型在绝大数情况下不能用来计算峰值吸收系数;在一定的温度范围和压强范围内,如果只考虑压强或温度的变化,由此计算的三种线型峰值(Gaussian,Lorentzian和Voigt)的相对误差大于0.1。因此,在计算线型峰值时,需考虑压强和温度同时变化对线型峰值的影响。最后分别讨论了甲烷、二氧化碳、一氧化碳及一氧化氮,得到与氟化氢结论相似的结论,结论的不完全相同是由于每种气体在波数、压力展宽系数、相对分子质量及温度系数上的不同而导致。     

精确测量石英晶体旋光率的光谱分析法

提出一种精确测量石英晶体旋光率的光谱分析法。利用光学矩阵方法对测量原理进行了分析,指出通过测量由两个平行放置的偏光镜和石英晶体所组成系统的透射曲线就可以精确计算出石英晶体的旋光率;并利用分光光度计设计实验,验证了该方法的正确性。对实验数据进行了处理,拟合出了旋光色散方程,对比Lowry的公式,所得出的公式在可见光范围内的更为精准。对实验数据进行了误差分析, 结果表明：选取厚的石英晶体,长的测量波段、低的扫描速度、小的狭缝宽度都有利于提高测量精度。     

Water Vapor Measurements between 590 and 2582 cm: Line Positions and Strengths

This study involves measurements of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O vapor spectra for the region between 590 and 2582 cm⁻¹. The parameters derived from the data include line positions, energy levels, and linestrengths. The study involves high-resolution line-position measurements with samples at room temperature in the (000)–(000), (010)–(010), and (010)–(000) bands. The experimental frequencies were used along with microwave, far-infrared, and hot water emission measurements in an analysis to obtain high-accuracy rotational energy level values in the (000), and (010) vibrational states of H₂¹⁶O forJ≤ 20. The experimental linestrengths were fitted by least squares to a model in which the dipole moment was represented as a series expansion containing up to 19 dipole moment matrix elements. The measurements in this work were more extensive than reported in prior studies by this author for the (010)–(000) band.     

Orientational Ordering of Tree Elements in the Dielectric Permittivity Model of a Forest Stand

Russian Physics Journal - The dielectric characteristics of trees are studied for a dielectric permittivity model of a forest stand of L1 band signals of navigation satellites. The contribution of...     

介质阻挡放电中不同厚度气隙内微放电通道的光谱特性研究

采用发射光谱法,研究了具有三层介质的介质阻挡放电中不同厚度气隙内微放电通道的等离子体参量的变化规律。与在传统的具有双层介质的介质阻挡放电系统中所产生的微放电通道不同,三层介质系统内微放电通道在光谱特性方面展现了完全不同的性质以及变化规律。实验发现,微放电通道在不同的放电气隙中具有不同的发光强度。利用氮分子第二正带系(C3Π_u→B3Π_g)的发射谱线以及对氮分子离子391.4 nm谱线强度与氮分子394.1 nm谱线强度之比的考察,实验进一步测量了氮分子(C3Π_u)的振动温度以及电子平均能量分别随氩气含量以及在不同电压下的变化规律。结果表明,当外加电压一定时,厚气隙内形成的微放电丝在分子振动温度以及电子平均能量上均低于薄气隙微放电丝。并且它们都随着氩气含量的增加而降低。随着电压的逐步升高,厚气隙内的微放电丝在以上两种参量上均基本保持不变,而薄气隙内微放电丝则出现较为明显的升高。这表明具有三层介质的介质阻挡放电中薄气隙较厚气隙对电压更为敏感且在相同电压浮动内电场变化范围更大。     

Measuring the Dielectric Permittivity of Sapphire at Temperatures 93–343 K

We consider a method for measuring the elements of the dielectric-permittivity tensor of a slightly lossy uniaxial anisotropic dielectric using the spectrum of resonance frequencies of a metal-dielectric resonator in the form of an axially anisotropic cylindrical specimen with endface metal mirrors. Measurements of both elements of the dielectric-permittivity tensor of sapphire at temperatures 93–343 K are performed using the spectrum of symmetric E modes. To avoid the influence of the residual gaps between the specimen and the mirrors, the endface surfaces of the specimen are metallized. We performed independent measurements of the axial and transverse elements of the permittivity tensor at room temperature from the spectra of azimuthal E modes and symmetric H modes. The values of the axial and transverse elements of the dielectric-permittivity tensor of sapphire in the range 93–343 K are presented with a spacing of 10 K.