色散耦合道光学模型对28Si的核子散射数据分析

在光学势中引入色散关系, 相比于通常的耦合道光学模型, 极大地减少了光学势 参数的个数. 采用基于软旋转子模型的耦合道方法对较轻形变核²⁸Si核的中子和质子散射实验数据进行了计算分析, 拟合得到一组色散光学势参数. 计算的中子总截面、以及中子、质子的弹性与非弹性散射微分截面与实验数据有较好的符合.     

固态交叉极化魔角旋转NMR中的极化转移

在普通有机固体中,直接键合的S和I自旋之间的偶极相互作用强于SI_n基团和其它质子之间的I-I耦合。因此,SI_n子系统中的相互作用支配了交叉极化过程中的自旋动力学,在这一新概念的指引下,样品魔角旋转时极化转移的理论和技术有了飞跃发展,特别是,各种新技术涌现出来,以提高高速魔角旋转时极化转移的效率。这些新技术的共同特点是仅调制射频辐射的位相或幅度,而保持高速度的魔角旋转不变。一系列谱编辑方法也已发展起来,它能依据相连质子的个数,产生碳的4个子谱,即C,CH,CH₂和CH₃子谱,这个技术已被用于一组煤样,在煤的CPMAS谱中,4种类型的碳谱是完全互相交迭在一起的,该技术的应用,已取得了令人鼓舞的成果。     

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。     

~(129)Xe核自旋极化转移增强分子的核磁共振信号

激光极化的12 9Xe核具有极高的非平衡极化度和长的弛豫时间 ,这一特点使得它能够极化转移增强液体、固体或者固体表面分子中原子核自旋极化。因而 ,提高了它们的核磁共振探测灵敏度和扩展了在材料和表面科学研究中的应用。综述激光极化12 9Xe核与其它分子中原子核之间的极化转移研究与进展 ,介绍相关物理机制和参数的测量。     

LHC能量下D介子的核修正因子

高能质子-质子(p-p)和质子-原子核(p-A)碰撞过程中产生的D介子是分析碰撞后生成的饱和胶子性质的重要途经。考虑领头阶下的强耦合效应,在色玻璃凝聚理论(CGC)框架下研究了LHC(Large Hadron Collider, LHC)能量下p-p(p-A)碰撞过程中的D介子产生。采用由KLR-AdS/CFT色偶极模型通过傅里叶变换得到的偶极关联因子,同时利用Glauber模型考虑冷核物质效应,计算了质心能量为5.02 TeV时质子-铅核(p-Pb)碰撞中不同碰撞中心度下D介子的产生截面,并在此基础上研究了p-Pb碰撞中D介子产生及其半轻子衰变过程中的核修正因子。通过与大型强子对撞机(LHC)实验结果比较发现:考虑强耦合效应后的理论结果与ALICE和LHCb合作组的最新实验数据符合得更好。最后,本文对LHC碰撞质心能量为8.16 TeV时p-Pb碰撞中D介子产生的核修正因子给出了理论预言, 结果显示此能量下核修正因子理论值比5.02 TeV时略大。     

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。     

SHA+脉冲序列用于g-C3N4样品15N-15N相关性的固体核磁共振研究

利用固体核磁共振实验研究了15N标记的g-C3N4样品中的15N-15N空间相关性,在高场和魔角旋转条件下对比两种不同的脉冲序列PDSD和SHA+的实验效果。发现当某个氮上连有质子的时候,脉冲序列SHA+比PDSD可以更好地检测15N原子间的极化转移。该研究可以为材料科学领域,特别是含氮掺杂的碳材料,提供一种有价值的研究方法。     

129Xe核自旋极化转移增强分子的核磁共振信号

激光极化的129Xe核具有极高的非平衡极化度和长的弛豫时间,这一特点使得它能够极化转移增强液体、固体或者固体表面分子中原子核自旋极化。因而,提高了它们的核磁共振探测灵敏度和扩展了在材料和表面科学研究中的应用。综述激光极化129Xe核与其它分子中原子核之间的极化转移研究与进展,介绍相关物理机制和参数的测量。     

质子辐照电荷耦合器件诱导电荷转移效率退化的实验分析

开展了电荷耦合器件（CCD）质子辐照损伤的实验研究. 分析了质子辐照CCD后电荷转移效率的退化规律,阐述了质子辐照诱导电荷转移效率退化的损伤机理,比较了不同能量质子对电荷转移效率的损伤程度. 通过开展辐射粒子输运理论计算,分析了不同能量质子对电荷转移效率损伤差异的原因. 关键词： 电荷耦合器件 质子 辐照效应 电荷转移效率     

选择性1NEPT技术及其在FX—90Q仪器上的应用

本文介绍一种~1H—~(13)C远程极化转移的脉冲序列.在JEOL FX—90QNMR波谱仪上实现了这种技术.对一些典型化合物的测定表明,选择性非灵敏核的远程极化转移增强法(SEL1NEPT)在测定季碳原子和进行谱带归属中,是一个有力的工具.     

Determination and assignment of heteronuclear long-range coupling constants. Methods based on semiselective INEPT

One-dimensional methods for the determination and assignment of heteronuclear ¹H-X (X = rare spin-z) coupling constants based on the semiselective polarization transfer via INEPT pulse sequence are proposed. Here the selectivity of the polarization transfer plays a positive role with respect to the sensitivity of the measurement and purity of the observed multiplets. In nonrefocused experiments the acquired antiphase multiplets enable an unambiguous assignment of long-range couplings of a preselected proton. The analysis of such multiplets is also discussed. In the refocused version the purging pulse (INEPT+) was used to provide pure in-phase multiplets. The spectral editing technique DISCO was applied to simplify the spectra and to extract the couplings from complex multiplets. Finally, the modified INEPT experiments which combine semiselective polarization transfer with selective proton decoupling are proposed.     

Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2

We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.     

Inverse polarization transfer for detecting in vivo 13C magnetization transfer effect of specific enzyme reactions in 1H spectra

The wide chemical shift dispersion and long T(1) of (13)C have allowed determination of in vivo magnetization transfer effects caused by aspartate aminotransferase and lactate dehydrogenase reactions using (13)C magnetic resonance spectroscopy. In this report, we demonstrate that these effects can be observed in the proton spectra by transferring the equilibrium magnetization of (13)C via the one-bond scalar coupling between (13)C and (1)H using an inverse insensitive nuclei enhanced by polarization transfer-based heteronuclear polarization transfer method. This inverse method allows a combination of the advantages of the long (13)C T(1) for maximum magnetization transfer and the high sensitivity of proton detection. The feasibility of this in vivo inverse polarization transfer approach was evaluated for detecting the (13)C magnetization transfer effect of aspartate aminotransferase and lactate dehydrogenase reactions from a 72.5-microl voxel in the rat brain at 11.7 T.     

Coulomb effects in polarization transfer in elastic antiproton and proton electron scattering at low energies

The influence of Coulomb distortion on the polarization transfer in elastic proton and antiproton electron scattering at low energies is calculated in a distorted-wave Born approximation. For antiproton electron scattering Coulomb effects reduce substantially the polarization transfer cross-section compared to the plane-wave Born approximation, whereas for proton electron scattering they lead to a dramatic increase for kinetic proton lab energies below about 20keV.     

Proton transport in ordered hydrogen-bonded solids

The proton transfer is considered in hydrogenbonded chains with asymmetric double-minimum potentials for proteons. The transport is described by the kinksoliton propagation in an energetically asymmetric double-well potential for a proton. The asymmetry can be caused by the spontaneous polarization in hydrogenbonded ferroelectrics, medium polarization in nonferroelectric hydrogen-bonded solids, crystallographic structure, geometry of the proton neighbourhood and internal electric field in biological macromolecules. The soliton dynamics of the system is analytically studied including the influence of a constant external electric field and damping mechanism. The velocity, energy, momentum and mobility of kinks are calculated.     

Incorporating homonuclear polarization transfer into PRESS for proton spectral editing: illustration with lactate and glutathione

A proton spectral editing pulse sequence for the detection of metabolites with spin systems that involve weak coupling is presented. The sequence is based on homonuclear polarization transfer incorporated into the standard PRESS (Point RESolved Spectroscopy) sequence, which is a volume-selective double spin echo method, to enable spatial localization. All peaks in the region of interest are initially suppressed whether they are peaks from the target metabolite or from contaminating background. The target signal is then restored by polarization transfer from a proton that has a resonance outside the suppressed region and to which the target spins are weakly coupled. This is achieved by the application of a 90 degrees hard pulse with phase orthogonal to that of the PRESS excitation pulse at the location of the first echo in PRESS and by optimizing the two PRESS timings, TE(1) and TE(2), for most efficient yield. Background signal not coupled to any protons outside the initially saturated region remains suppressed. The advantage of this sequence compared to multiple quantum filters is that signal from singlet peaks outside the suppressed area are preserved and can thus be used as a reference. The efficacy of the sequence was verified experimentally on phantom solutions of lactate and glutathione at 3.0 T. For the AX(3) spin system of lactate, the sequence timings were optimized by product operator calculations whereas for the ABX spin system of the cysteinyl group of glutathione numerical calculations were performed for sequence timing optimization.     

Angular Dependence of the Polarization Transfer to the Proton in the $$e\vec {p} \to e\vec {p}$$ Process

JETP Letters - The dependence of the longitudinal polarization transfer to the proton in the $$e\vec {p} \to e\vec {p}$$ process on the proton scattering angle has been numerically analyzed for the...     

Conformal couplings and “azimuthal matching” of QCD pomerons

Using the asymptotic conformal invariance of perturbative QCD we derive the expression of the coupling of external states to all conformal spin p components of the forward elastic amplitude. Using the wave function formalism for structure functions at small x, we derive the perturbative coupling of the virtual photon for , which is maximal for linear transverse polarization. The non-perturbative coupling to the proton is discussed in terms of “azimuthal matching” between the proton color dipoles and the configurations of the photon. As an application, the recent conjecture of a second QCD pomeron related to the conformal spin-1 component is shown to rely upon a strong azimuthal matching of the component in –proton scattering. Received: 25 October 1999 / Revised version: 19 January 2000 / Published online: 14 April 2000     

Evaluation of a Shuttle DNP Spectrometer by Calculating the Coupling and Global Enhancement Factors of l-Tryptophan

A liquid state shuttle dynamic nuclear polarization (DNP) spectrometer is presented, featuring several technical modifications that increase stability and improve reproducibility. For the protons of l-tryptophan, the signal enhancement and the DNP spin properties, such as relaxation, were measured and compared with each other. The calculated coupling factors suggest that the proton accessibility for the polarizer molecule has an important influence on the DNP enhancement. In general, short proton spin longitudinal relaxation times without radical reduce the detectable enhancement by decreasing the leakage factor and increasing the relaxation losses during the course of the sample transfer. The usage of a global enhancement factor gives a more complete overview of the capabilities for the described experimental setup. Global enhancements of up to ?4.2 for l-tryptophan protons are found compared to pure Boltzmann enhancements of up to ?2.4.     

A study of coupled-reaction channel effects in the36S +37Cl system,hybridization between single particle orbits

Elastic and inelastic scattering as well as transfer transitions involving a valence proton in thesd- andfp- shell orbits are studied in the interaction of³⁷Cl +³⁶S at E_CM=50 MeV. Experimental angular distributions of single particle states of³⁷Cl (elastic and inelastic transfer) are presented with a CRC analysis. In the CRC calculations the effects of inelastic and transfer couplings are studied using known spectroscopic information. In the CRC analysis six single particle bound states and the collective 2⁺ excitation of³⁶S are included in the coupling scheme. Higher order coupling effects are found to be important. A distinct effect, the mixing of single particle states (of different parity) due to direct and transfer interactions is observed to produce an enhancement of the transfer cross section to the low lying states. This feature is due to a change of the asymptotically defined single nucleon orbits via polarization in the field of the other nucleus, an effect which is analogous to hybridization, known from atomic physics.