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...     

Pressure Broadening of the Rotational Line of Oxygen at 425 GHz

The pressure broadening of the ¹⁶O¹⁶O rotational line (N, J)=(3, 2)-(1, 2) at 425 GHz by oxygen and nitrogen perturbers at room temperatures have been reported. A spectrometer with BWO and acoustic detector was employed with a double magnetically shielded cell. The signal-to-noise ratio on the line was about 200-250 for self-broadening and about 100 for broadening by N₂ measurements. The pressure-broadening parameters of the line at room temperature (23±0.5°C) were measured as 2.19±0.01 MHz/Torr for self-broadening and 2.215±0.02 MHz/Torr for broadening by nitrogen. Values of these parameters significantly (by about 25%) differ from ones previously measured by H. M. Pickett, E. A. Cohen, and D. E. Brinza, (Astrophys. J.248, L49-L51 (1981)). The results of the present work show the necessity for correction of broadening parameters of this line for the purpose of Earth atmosphere remote sensing. The central frequency of the transition (N, J)=(3, 2)-(1, 2) was measured as 424 763.023±0.020 MHz.     

Consequences of Inhomogeneous Broadening on Fluorescence Line Narrowing Spectra

Fluorescence line narrowing is a sensitive tool to monitor subtle changes in protein conformation. We restudied the consequences of inhomogeneous broadening on the observed spectra. Vibronic absorption bands of systems with weak electron-phonon coupling can be described by a lorentzian function with width of the order of a few centimeters. For an ensemble of molecules with closely spaced electronic transitions, a single laser frequency will excite many molecules through the broad base (tail) of the lorentzian function. This, along with excitation of low-frequency modes, contributes to the unresolved background observed in line-narrowed spectra. Examples are shown for Zn cytochrome c, a fluorescent derivative of Fe cytochrome c. Spectra are compared for the protein in two solvents: glycerol/water or trehalose. Two types of cytochrome, from horse and yeast, are also compared.     

The Nature of Line Broadening in Thermally Detected 57FeFe NMR

⁵⁷FeFe with isotopic concentrations from 15 to 95% is studied using NMR thermally detected by nuclear orientation. Lines are found to be consistently homogeneous. The contrast with previous inhomogeneous ⁵⁷FeFe lines from Mössbauer detected NMR is explained by differences in radio frequency field strength.     

Path Integral Formalism for Line Broadening in Plasmas: Lyman‐α case

Using the path integral formalism, the fine structure and dynamics effects are taken into account for the study of the spectral line broadening in plasmas. A compact expression of the dipolar autocorrelation function (DAF) for an emitter in the plasma is derived for Lyman alpha lines with fine structure. The expression of the DAF takes into account the dynamics effects, which are represented by the time autocorrelation function of the electric microfield. The spectral line for the Lyman‐alpha case has been obtained in a compact form and plotted in the quasi‐static approximation and compared to a line obtained by a simulation. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quantum Interference Line Shifts of Broad Dipole‐Allowed Transitions

High‐resolution laser spectroscopy serves the purpose of determining the energy difference between states of atoms and molecules with the best possible accuracy. Therefore, one may face the problem of finding the center of a symmetric line within a small fraction of the line width, or one needs to extract the energy difference from an asymmetric line without a uniquely defined center. Multiplets of atomic resonance lines are subject to mutual line pullings and give rise to asymmetric line distortions due to quantum interference. This paper reviews the treatment of these distortions for dipole‐allowed one‐photon transitions. Specific examples are given for hydrogen and helium spectroscopy.     

利用光学-光学双共振研究谱线的碰撞增宽

利用光学-光学双共振光谱技术研究了NaK分子21Σ＋→６1Σ＋跃迁线的碰撞增宽。一台单模半导体激光器实现11Σ＋(v″,J″)→21Σ＋(v′,J′)的跃迁,另一单模半导体激光器激发21Σ＋(v′,J′)能级到６1Σ＋的振转能级,二激光束反向平行通过样品池。谱线总线宽与K原子密度成线性关系,由其斜率得到增宽速率系数k_br＝(1.4±0.7)×10-8 cm3·s-1。同时研究了21Σ＋(v＝8,J＝12)→21Σ＋(v＝8,J＝13,14)转动能级间的碰撞激发转移,测量谱线的相对强度,由速率方程得到碰撞转移速率分别为6.1×106和5.2×106 s-1。     

二价钐离子谱线的非均匀加宽、荧光窄化和永久性光谱烧孔

基于光谱烧孔在高密度光存储中的可能应用,研究了谱线非均匀加宽、荧光谱线窄化、高温永久性光谱烧孔、烧孔机理、烧孔动力学过程和光谱孔的热稳定性。在国际上率先设计并研制出二价钐离子掺杂碱土金属氟卤化物混晶高温光谱烧孔体系,实现了室温永久性光谱烧孔,获得了室温寿命300h的光谱孔。利用时间分辨光谱分离出非均匀线形内的各局域组态,比较烧孔前后光谱再分布证实了三价钐离子的电子陷阱作用。利用Block理论分析了烧孔动力学过程。     

Degrees of Freedom of a K-User Interference Channel in the Presence of an Instantaneous Relay

In this paper, we study the degrees of freedom (DoF) of a frequency-selective K-user interference channel in the presence of an instantaneous relay (IR) with multiple receiving and transmitting antennas. We investigate two scenarios based on the IR antennas’ cooperation ability. First, we assume that the IR receiving and transmitting antennas can coordinate with each other and that the transmitted signal of each transmitting antenna can depend on the received signals of all receiving antennas, and we derive lower and upper bounds for the sum DoF of this model. In an interference alignment scheme, we divide receivers into two groups called clean and dirty receivers. We design our scheme such that a part of the messages of clean receivers can be de-multiplexed at the IR. Thus, the IR can use these message streams for an interference cancellation at the clean receivers. Next, we consider an IR, the antennas of which do not have coordination with each other and where the transmitted signal of each transmitting antenna depends only on the received signal of its corresponding receiving antenna. We also derive lower and upper bounds for the sum DoF for this model of IR. We show that the achievable sum DoF decreases considerably compared with the coordinated case. In both of these models, our schemes achieve the maximum K sum DoF if the number of transmitting and receiving antennas is more than a finite threshold.     

Interference of Two-Component Bose-Einstein Condensates with a Coupling Drive in Presence of Dissipation

The interference of the two-component Bose-Einstein condensates with a coupling drive in the presence of the dissipation is studied. We find that when the two-component Bose-Einstein condensates are initially in the coherent states, for the smaller dissipation parameters compared with that of the rf frequency ωrf, the interference intensity exhibits damply oscillation behavior, whereas when the dissipation parameters are larger than that of the ωry, the interference intensity exhibits a fast attenuation behavior. As a comparison, the interference intensity in the absence of the dissipation is also studied. We conclude that the dissipation of the system can be evaluated by selecting the ωrf experimentally.     

Interference of Two-Component Bose-Einstein Condensates with a Coupling Drive in Presence of Dissipation

The interference of the two-component Bose-Einstein condensates with a coupling drive in the presence of the dissipation is studied. We find that when the two-component Bose-Einstein condensates are initially in the coherent states, for the smaller dissipation parameters compared with that of the rf frequency ωrf, the interference intensity exhibits damply oscillation behavior, whereas when the dissipation parameters are larger than that of the ωrf, the interference intensity exhibits a fast attenuation behavior. As a comparison, the interference intensity in the absence of the dissipation is also studied. We conclude that the dissipation of the system can be evaluated by selecting the ωrf experimentally.     

Numerical Analysis of Emission Line Broadening under Coulomb Interaction in an Electron–Hole System

A numerical analysis of the energy spectrum of an ensemble of interacting particles in a two-dimensional system has been performed by means of direct solution of the microparticle Schröedinger equation. Comparison of the numerical calculations of the form factor of the homogeneous broadening of spectral lines with the results obtained according to perturbation theory has been made. The range of applicability of the universal relation between the amplification and emission spectra is discussed.     

Competition of Short-Range and Long-Range Mechanisms of Spectral Line Broadening in Emission of Atomic and Molecular Gases

An analogy is shown for broadening the spectral line of atoms in the case of competition between the short-range Doppler broadening mechanism and the long-range impact mechanism in atomic gases, as well as for the absorption band of a molecular gas in the infrared (IR) region of the spectrum, where the longrange part of the spectrum is also determined by the impact mechanism of the broadening. The long-range part in the pedestal region of the absorption band is associated with the distribution of molecules over the rotational states, and, in the range of wings of the absorption band, it is due to a finite time of collisions between emitting and perturbed molecules. The flux of resonant radiation produced by an excited atomic gas is estimated using the concepts of the spectral absorption band and a large optical thickness of the gas. These concepts are used for a molecular gas where, in the framework of the regular model (the Elsasser model), expressions are given for the absorption coefficient related to a specific spectral absorption band, separately in the pedestal region and for wings of the absorption band. As a demonstration of the possibilities of these concepts, the IR flux is calculated on the surface of Venus from its atmosphere, which includes seven vibrational transitions of the carbon dioxide molecule and amounts to 26% of the total flux of IR radiation emitted by the Venus surface. An analysis of the Venus energy balance leads to the conclusion that the main part of IR radiation of the Venus atmosphere falling on its surface is formed by a microscopic dust in the Venus atmosphere. This channel of the Venus energy balance is realized if the mass of a microscopic dust in the Venus atmosphere is seven orders of magnitude less than the mass of atmospheric carbon dioxide.     

Line Broadening and Enthalpy: Some Empirical Calibrations of Solid Solution Behaviour from IR Spectra

Following recent developments in the application of autocorrelation analysis of line broadening in powder absorption IR spectra, the possibility that elastic strain heterogeneities are responsible both for such broadening and for enthalpy variations in solid solutions has been explored systematically. Recent data for five silicate solid solutions, augite-jadeite, almandine-grossular, albite-anorthite, anthophyllite-grunerite and clinoenstatite-clinoferrosilite, are reviewed. Variations in the autocorrelation parameter for line broadening, j corr, scale linearly with calorimetric data for enthalpy variations, j H , associated with cation substitutions and ordering in these systems. It is proposed that, while there may not be a universal calibration of j H in terms of j corr for all structures, it should be possible to produce empirical calibrations for groups of solid solutions with the same basic structure. Variations in j corr at different phonon frequency ranges provide additional insights into the structural mechanisms by which ordering, mixing, displacive and reconstructive processes occur in silicate solid solutions.     

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference (CQI) was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken, from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.     

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference （CQI） was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken,from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.     

用迈克尔逊干涉仪测量金属的线膨胀系数

将迈克尔逊干涉仪的精确测量和金属线膨胀系数的PID温度控制测量方法相结合,被测金属样品被加热后会发生长度的变化,从带动镜面产生微小移动,进而引起迈克尔逊光路中两束光的光程差的改变,通过干涉条纹记录温度变化时干涉条纹的变化数量,以实现对金属热胀系数的精确测量。     

差分吸收大气CO2激光雷达的大气压力增宽修正算法

CO2作为温室气体主要成分对全球气候有重要的影响。现有的被动观测设备都只能获得单点上空的CO2浓度值,而差分吸收激光雷达在探测CO2方面具有巨大优势,可以获得较高的时空分辨率。然而,在利用差分吸收激光雷达探测CO2浓度时,其中的压力增宽有不可忽视的重要影响。基于此着重对压力增宽进行分析,提出新的修正算法,新方法同经典算法相比较,减小了反演过程中的误差。实验中分别对一例仿真信号和实测信号进行反演,最终获得了CO2浓度垂直廓线分布较为理想的结果,验证了新修正算法的可行性。