一种新的DEPT 谱编辑方法

提出一种新的基于多元线性回归计算的无畸变极化转移增益法(DEPT)谱编辑方法．该方法使用多元线性回归对谱图中的杂信号进行拟合,获得最佳拟合系数,然后将拟合系数代入拟合公式,通过该公式对DEPT 子谱进行计算,去除杂信号,最终分别得到纯净的CH₃、CH₂、CH 子谱图．实验结果证明,使用新方法对DEPT 谱进行编辑能够很好地减少杂信号的干扰,得到只含有CH_n 信号的子谱．新方法为碳谱的解析尤其是复杂和密集的谱线的解析提供了方便．     

应用二维谱学技术归属泰妥拉唑的1H和13C NMR

应用DEPT（无畸变极化转移增强谱）、HMQC（异核多量子相干谱）、HMBC（异核多键相干谱）、¹H-¹H COSY（相关谱）、NOESY（核欧沃豪斯谱）和 TOCSY（全相关谱）谱学技术,对泰妥拉唑所有的氢进行了归属. 不对称硫原子引起邻接CH₂ 2个氢化学位移不等价;该2个氢相互偶合,其偶合常数为12.9 Hz;借助DEPT谱,2个甲氧基被区别;借助DEPT和TOCSY谱,另2个与碳相连的甲基被区分;利用HMBC谱,所有的碳峰可以归属.      

应用二维谱学技术归属泰妥拉唑的1H和13C NMR

应用DEPT（无畸变极化转移增强谱）、HMQC（异核多量子相干谱）、HMBC（异核多键相干谱）、¹H-¹H COSY（相关谱）、NOESY（核欧沃豪斯谱）和 TOCSY（全相关谱）谱学技术,对泰妥拉唑所有的氢进行了归属. 不对称硫原子引起邻接CH₂ 2个氢化学位移不等价;该2个氢相互偶合,其偶合常数为12.9 Hz;借助DEPT谱,2个甲氧基被区别;借助DEPT和TOCSY谱,另2个与碳相连的甲基被区分;利用HMBC谱,所有的碳峰可以归属.      

一对阻转异构体NMR谱的解析

本文报道一个孕甾生物碱-富贵草碱A的阻转异构现象,并报道利用无畸变极化转移增强(DEPT)技术、异核化学位移相关谱(HETCOR)、质子NOE谱(NOESY)这些核磁共振技术,对表富贵草碱A的一对阻转异构体的¹³C NMR化学位移数据,作了完整指定,表富贵草碱A为一对阻旋异构体的混合物,这是孕甾生物碱中的一个阻旋异构现象。     

掺杂LiF的ESR谱和ENDOR谱研究

LiF:Mg,Cu热释光(TL)磷光体在γ辐照后产生F⁰顺磁中心,其g因子为g_xx=2.0030,g_yy=2.0450,g_zz=2.0251,裂分为A_xx=511.04G,A_yy=505.42G,A_zz=507.26G。F⁰中心的浓度随Mg⁺⁺浓度的增加而下降。磷光体的ENDOR谱显示F⁰中心附近有铜核存在。照射前和照射后24h测量均未发现Cu⁺⁺的ESR谱,表明铜是以Cu⁺形式掺入的,照射并未引起Cu⁺离子化合价的改变。LiF:Mg,Cu,P在γ辐照前具有轴对称的Cu⁺⁺离子的ESR谱,辐照后产生了O^-空穴中心和PO₃^2-自由基,改变了Cu⁺⁺的环境,使Cu⁺⁺的谱发     

一对阻转异构体NMR谱的解析

本文报道一个孕甾生物碱—富贵草碱A的阻转异构现象,并报道利用无畸变极化转移增强(DEPT)技术、异核化学位移相关谱(HETCOR)、质子NOE谱(NOESY)这些核磁共振技术,对表富贵草碱A的一对阻转异构体的~(13)C NMR化学位移数据,作了完整指定,表富贵草碱A为一对阻旋异构体的混合物,这是孕甾生物碱中的一个阻旋异构现象。     

锡偶联无规溶聚丁苯橡胶13C NMR研究(Ⅰ)烷碳区谱峰归属

研究了锡偶联溶聚丁苯橡胶烷碳区¹³C NMR谱图,借助DEPT谱区分CH和CH₂,利用文献值和经验计算公式,对实验中观察到的24个谱峰进行了归属.     

阿扑西林结构确证的谱学研究

对青霉素类抗生素阿扑西林的红外光谱（IR）、紫外光谱（UV）、核磁共振氢谱（¹H NMR）、氢氢相关谱（¹H-¹H COSY）、核磁共振碳谱（¹³C NMR）、DEPT谱、碳氢相关谱（HSQC）、质谱（MS）进行了解析,对其所有的NMR谱信号进行了归属,同时讨论了质谱的主要碎片离子的可能的裂解方式和红外特征吸收峰所对应的官能团的振动形式. 通过多种波谱技术确证了阿扑西林的结构.     

天然结晶辣椒碱的NMR谱研究

用一维¹H NMR谱、¹H-¹H COSY谱和一维¹³C NMR谱、DEPT谱研究辣椒碱分子和二氢辣椒碱分子及其混合物,得到¹H和¹³C的化学位移,采用¹H NMR谱测定天然辣椒碱中辣椒碱和二氢辣椒碱的相对含量.     

一种热转印色素的1H、13C NMR研究

报道了一种热转印色带用黄染料的¹H、¹³C NMR , 应用¹H NMR、¹³C NMR、定量碳谱、DEPT、¹H-¹H COSY、HMQC、HMBC等确定了其在氘代氯仿中的分子结构, 并对全部谱峰进行了归属, 探索了黄染料在氘代氯仿中的结构对¹³C、¹H NMR谱图化学位移及谱峰裂分的影响.      

J-modulation effects in DOSY experiments and their suppression: the Oneshot45 experiment

Diffusion-ordered spectroscopy (DOSY) is a powerful NMR method for identifying compounds in mixtures. DOSY experiments are very demanding of spectral quality; even small deviations from expected behaviour in NMR signals can cause significant distortions in the diffusion domain. This is a particular problem when signals overlap, so it is very important to be able to acquire clean data with as little overlap as possible. DOSY experiments all suffer to a greater or lesser extent from multiplet phase distortions caused by J-modulation, requiring a trade-off between such distortions and gradient pulse width. Multiplet distortions increase spectral overlap and may cause unexpected and misleading apparent diffusion coefficients in DOSY spectra. These effects are described here and a simple and effective remedy, the addition of a 45° purging pulse immediately before the onset of acquisition to remove the unwanted anti-phase terms, is demonstrated. As well as affording significantly cleaner results, the new method allows much longer diffusion-encoding pulses to be used without problems from J-modulation, and hence greatly increases the range of molecular sizes that can be studied for coupled spin systems. The sensitivity loss is negligible and the added phase cycling is modest. The new method is illustrated for a widely-used general purpose DOSY pulse sequence, Oneshot.     

DEPTQ: Distorsionless Enhancement by Polarization Transfer Including the Detection of Quaternary Nuclei

A pulse sequence DEPTQ yielding the signals and multiplicity information for all carbon types including the signals of quaternary carbons and encompassing all the known advantages of the basic DEPT experiment is proposed. Its behavior has been studied theoretically and experimentally and has been compared critically with alternative methods dedicated for the same purpose. Its marked insensitivity to experimental parameters and its potential for complete and efficient spectral editing makes DEPTQ the ideal experimental platform for a semi- or fully automated analysis of 1D¹³C spectra.     

Time-resolved spectral analysis of transient processes in Fabry-Perot interferometers

Parameters of a spectrochronograph that represents a Fabry-Perot interferometer combined with a spatial-time analyzer (a streak camera) are analyzed. Using numerical simulation, time scans of interferograms for bandwidth-limited and phase-modulated pulsed optical signals are obtained. The conditions are determined under which a Fabry-Perot interferometer represents a high-accuracy instrument for measuring the timeresolved spectral dynamics of short optical signals. In particular, an adequate representation of relatively smooth and monotone changes in amplitude and phase characteristics of an optical signal in a spectrochronograph requires that the mode lifetime in a Fabry-Perot interferometer be matched to the time scale of changes in the spectral structure of a pulse being studied. The character of distortions formed in the time-resolved spectral patterns in the case where these conditions are not fulfilled is qualitatively determined, and quantitative estimates of the distortions are presented. The results of the analysis and the numerical calculations show that a spectrochronogram obtained using a Fabry-Perot interferometer and a time analyzer (a streak camera) with parameters corresponding to the criteria formulated in the paper enable one to obtain information on the initial amplitude-phase pattern of a light pulse.     

A "magic sandwich" pulse sequence with reduced offset dependence for high-resolution separated local field spectroscopy

A pulse sequence for high resolution separated local field spectroscopy based on "magic sandwich" elements is demonstrated on a single crystal sample. Simulations and experimental results show that this pulse sequence has a reduced frequency offset dependence compared to PISEMA (polarization inversion spin exchange at the magic angle). As a result, it has a larger effective range of homonuclear decoupling, reduced zero-frequency spectral distortions, and more reliable scale factors for individual resonances. In addition, it is easier to setup on commercial spectrometers.     

组合脉冲宽带激发2H-平均哈密顿理论计算研究

四级核回波实验通常需要射频脉冲能够激发谱宽超过100 kHz 的信号．在最近的研究中,作者发现组合脉冲COM-II (9018090135 45) 能够在氘核的四级核回波实验中实现宽带激发．此外,作者还结合了八步相位循环的方法,有效消除了由有限脉宽效应造成的谱图扭曲现象．利用了平均哈密顿原理,对该方法进行了理论计算研究．作者采用了自旋为1 的矩阵算符,通过计算解释了八步相位循环能够消除谱图扭曲的原因．     

Regularities of radio-pulse propagation in transparent dispersive media

The distortions of pulsed radio signals in passage through a dispersive medium with a quadratic phase function are examined. These distortions are determined quantitatively by the relative pulse broadening. Analysis shows that the degree of envelope distortion is determined by a single dimensionless parameter and is practically independent of the signal spectrum. This parameter, which is called dispersion disphasing over the spectral interval, is easily calculated and is very useful for estimation of the degree of radio-pulse broadening. An example of its use for the simple case of pulse propagation through a parabolic ionospheric layer is provided.Moscow Physicotechnical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 9, pp. 943–951, September, 1993.     

Spectral Artifacts Resulting from Multiple-Quantum Coherence Transfers by Spin Decoupling during Acquisition

Off-resonance coherent decoupling of spin X in a heteronuclear SX_N spin system can result in a multiplet with overlapping lines of spin Sand an overall shape similar to that of a doublet. Such lineshape distortions occur if certain multiple-spin coherences are present when the decoupler is switched on. The distortion could cause an apparent change in the multiplicity of an M + 1 multiplet of an SX_NY_M spin system when a selective decoupling of spins X is applied after a polarization transfer from spins X to spin S by INEPT or DEPT. Possibilities for suppressing the distortions are discussed.     

Investigation of the effect of a variety of pulse errors on spin I=1 quadrupolar alignment echo spectroscopy

We report on an analysis of a well known three-pulse sequence for generating and detecting spin I=1 quadrupolar order when various pulse errors are taken into account. In the situation of a single quadrupolar frequency, such as the case found in a single crystal, we studied the potential leakage of single and/or double quantum coherence when a pulse flip error, finite pulse width effect, RF transient or a resonance offset is present. Our analysis demonstrates that the four-step phase cycling scheme studied is robust in suppressing unwanted double and single quantum coherence as well as Zeeman order that arise from the experimental artifacts, allowing for an unbiased measurement of the quadrupolar alignment relaxation time, T(1Q). This work also reports on distortions in quadrupolar alignment echo spectra in the presence of experimental artifacts in the situation of a powdered sample, by simulation. Using our simulation tool, it is demonstrated that the spectral distortions associated with the pulse artifacts may be minimized, to some extent, by optimally choosing the time between the first two pulses. We highlight experimental results acquired on perdeuterated hexamethylbenzene and polyethylene that demonstrate the efficacy of the phase cycling scheme for suppressing unwanted quantum coherence when measuring T(1Q). It is suggested that one employ two separate pulse sequences when measuring T(1Q) to properly analyze the short time behavior of quadrupolar alignment relaxation data.     

New method of control over the phase of an ultrashort electromagnetic pulse under frustrated total internal reflection conditions

A new method of operational control over the phase of an ultrashort pulse in the range from 0 to π with insignificant phase distortions is proposed. The results of the experiment on control within 0.7 π over the phase of a terahertz pulse with a relative spectral width exceeding an octave are presented.