Scapolite中S2-中心的电子顺磁共振研究

对发光的天然晶体Scapolite中S2-分子中心进行了顺磁共振研究。仔细地测量了共振g-张量主值的角度变化,从而使我们能够确定S-S键轴和p-函数方向在晶体中的取向。超精细线和超超精细线的研究表明晶体中S2-中心的存在以及S2-中心的电子自旋和两个近邻Cl-离子核自旋的相互作用。     

DFT study of sulfur centred radicals formed in 5-methylcytosine hemihydrate crystal doped with 5-methyl-2-thiocytosine

Two 5-methyl-2-thiocytosine (5-MTC) radical species formed in 5-methylcytosine hemihydrate crystal lattice have been investigated by means of g-tensor and spin density distribution calculation using the B3LYP density functional. Theoretical values have been compared with experimental data for g-tensor eigenvectors. In model structures containing more molecules, significant difference of spin density localization on 5-MTC has been found for radical cation (radical I) in comparison to neutral radical of cationic origin (radical II). The structure of the radical centre as well as the mechanism of charge transfer and radical stabilization on 5-MTC in this system has been proposed.     

Structural models of radiational paramagnetic centers in alkali-tellurite glasses

The nature of the radiational ESR centers in binary alkali-tellurite glasses is discussed, and the most likely models of the molecular structure and the energy levels of the centers are given. It is shown that the paramagnetic properties of the centers (g-tensor symmetry, values of the g-tensor components as a function of the glass composition and the phase state of the system) are satisfactorily described if the centers are taken to be the inorganic radicals TeO ₂ ^– and TeO ₄ ^3– .Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 15–21, December, 1976.     

Theoretical prediction of intrinsic self-trapping of electrons and holes in monoclinic HfO2

We predict, by means of ab initio calculations, stable electron and hole polaron states in perfect monoclinic HfO2. Hole polarons are localized on oxygen atoms in the two oxygen sublattices. An electron polaron is localized on hafnium atoms. Small barriers for polaron hopping suggest relatively high mobility of trapped charges. The one-electron energy levels in the gap, optical transition energies and ESR g-tensor components are calculated.     

Electron spin-relaxation via vibronic level of nickel (I) and nickel (III) cyanide complexes in NaCl single crystals

Electron spin-lattice relaxation rates for the low spin [Ni(CN)(4)](1-) and [Ni(CN)(4)](3-) complexes in NaCl host lattice were measured by the inversion recovery technique in the temperature range 7-50K. The data for both paramagnetic species fit very well to a relaxation process involving localized anharmonic vibration modes, also responsible for the g-tensor temperature dependence.     

Modulation effects of rotating radiofrequency field in forward nuclear scattering of synchrotron radiation

The quantization of a nuclear angular momentum in the rotating hyperfine (HF) field of any frequency is theoretically studied in resonant forward scattering of synchrotron radiation (SR). The adiabatically slow rotation of the quantization axis does not perturb the multilevel structure of nuclear states created by the static hyperfine interaction. It follows directly from the pattern of quantum beats of a resonant response (RR) to an SR pulse. When the rotation frequency is of the order of the Larmor frequencies, determining the stationary HF sublevels, the pattern of quantum beats of an RR is formed by the nuclear resonant transitions between quasienergy levels. At the rotation frequency much larger than the Larmor frequencies the multilevel structure of nuclear states results from the quadrupole interaction only. This revised version was published online in August 2006 with corrections to the Cover Date.     

Temperature dependence of17O and14N NQR frequencies in commercial TNT

The temperature dependence of the¹⁷O nuclear quadrupole resonance (NQR) frequencies has been measured in commercial trinitrotoluene by highly sensitive nuclear quadrupole double resonance techniques. The¹⁴N NQR frequencies have been measured in the same sample for comparison. In contrast to the¹⁴N quadrupole coupling constant, the¹⁷O quadrupole constant increases with increasing temperature.     

The nuclear spin interaction with paramagnetic impurities in antiferromagnets

The influence of paramagnetic impurities on the relaxation frequencies of the nuclear subsystem in antiferromagnets is investigated. In the framework of the spin operator diagram technique the nuclear spin-spin as well as spin-lattice relaxation rates are calculated. The correlation effects due to indirect spin-spin interaction via magnons both in nuclear and impurity subsystems are taken into account.     

Temperature dependence of chlorine NQR in 2-chloro 5-nitrobenzoic acid and 4-chloro 3-nitrobenzoic acid

Temperature dependence of chlorine nuclear quadrupole resonance in 2-chloro 5-nitrobenzoic acid and 4-chloro 3-nitrobenzoic acid has been investigated in the region 77° K to room temperature. No phase transition has been observed. The results are analysed to obtain the torsional frequencies and their temperature dependence. A nonlinear temperature dependence is obtained for the torsional frequencies.     

Optical ac Stark Effect in ~(23)Na NMR Spectra

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Electrical detection of coherent nuclear spin oscillations in phosphorus-doped silicon using pulsed ENDOR

We demonstrate the electrical detection of pulsed X-band electron nuclear double resonance (ENDOR) in phosphorus-doped silicon at 5 K. A pulse sequence analogous to Davies ENDOR in conventional electron spin resonance is used to measure the nuclear spin transition frequencies of the (31)P nuclear spins, where the (31)P electron spins are detected electrically via spin-dependent transitions through Si/SiO(2) interface states, thus not relying on a polarization of the electron spin system. In addition, the electrical detection of coherent nuclear spin oscillations is shown, demonstrating the feasibility to electrically read out the spin states of possible nuclear spin qubits.     

核磁共振实验原理及数据分析

从量子角度阐明了核磁共振的基本原理,测定了水和聚四氟乙烯的核磁共振频率,计算了对应样品的旋磁比。     

Application of field-cycling NMR relaxometry to the study of ultrasound-induced effects in the molecular dynamics and order of mesomorphic materials

A salient characteristic of nuclear magnetic resonance (NMR) techniques is the possibility to scan nuclear spin evolutions within a broad Larmor frequency range. Special instrumentation was developed to extend nuclear spin relaxation studies up to proton Larmor frequencies in the sub-kilohertz regime, a technique known as field-cycling NMR relaxometry. This article refers to an experimental version where the sample under study is selectively subjected to ultrasonic irradiation. The fact that ultrasound couples selectively to the collective dynamics of liquid crystals, offers new insights for the study of the molecular dynamics in these materials using NMR relaxation.     

Manifestations of Electron–Nuclear Interactions in the High-Frequency ENDOR/ODMR Spectra for Triplet Si–C Divacancies in 13C-Enriched SiC

JETP Letters - The frequencies of electron–nuclear interactions with 13C and 29Si nuclei on remote coordination spheres are determined in triplet spin centers in the form of neutral...     

Volume variation of nuclear Grüneisen parameter for equation of state studies

The method of first principle pseudopotential is used to simulate the volume variation of nuclear Grüneisen parameter. The elements Al and Be, for which Neal’s experimental data exist are investigated. The nuclear Grüneisen obtained from the details of phonon frequencies are in better agreement with the experimental data as compared to those obtained from approximate Slater and Dugdale-MacDonald methods, often used in shock wave studies.     

Semiclassical description of isoscalar giant multipole resonances

The scaling approximation in a semiclassical theory of nuclear collective motions based on the Vlasov equation is applied to the study of isoscalar giant resonances. Analytic forms are obtained for the frequencies of any multipolarity, expressed just in terms of local density distributions, using realistic nuclear effective forces. The importance of non local interactions and diffuse surfaces is clearly shown. The limits of the scaling picture in describing high multipolarity resonances are finally discussed.     

On the theory of mixing-frequency electron spin-echo envelope modulation spectroscopy

It has recently been stated that the parametrization of the time variables in the one-dimensional (1-D) mixing-frequency electron spin-echo envelope modulation (MIF-ESEEM) experiment is incorrect and hence the wrong frequencies for correlated nuclear transitions are predicted. This paper is a direct response to such a claim, its purpose being to show that the parametrization in 1- and 2-D MIF-ESEEM experiments possesses the same form as that used in other 4-pulse incrementation schemes and predicts the same correlation frequencies. We show that the parametrization represents a shearing transformation of the 2-D time-domain and relate the resulting frequency domain spectrum to the HYSCORE spectrum in terms of a skew-projection. It is emphasized that the parametrization of the time-domain variables may be chosen arbitrarily and affects neither the computation of the correct nuclear frequencies nor the resulting resolution. The usefulness or otherwise of the MIF parameters |ψ| > 1 is addressed, together with the validity of the original claims of the authors with respect to resolution enhancement in cases of purely homogeneous and inhomogeneous broadening. Numerical simulations are provided to illustrate the main points.     

Connection between Zero-Sound Excitations in Symmetric and Asymmetric Nuclear Matter

Physics of Atomic Nuclei - A method for calculating frequencies of zero-sound excitations in symmetric and isospin-asymmetric nuclear matter is presented. In asymmetric matter, three branches of...     

Electronic structure and lattice dynamics of domeykite Cu<Subscript>3</Subscript>As according to nuclear quadrupolar resonance of<Superscript>75</Superscript>As and<Superscript>63,65</Superscript>Cu

The temperature dependences of nuclear quadrupole resonance (NQR) frequencies, the line width and nuclear relaxation of⁷⁵As and^63,65Cu, as well as the electrical resistivity in domeykite Cu₃As are studied in the temperature range of 4.2-300 K. The comparison of the calculated with the measured lattice contribution to the NQR frequencies points at a substantial role played by the conduction electrons in creating the electric field gradient at the nuclei sites. The temperature dependence of the copper and arsenic nuclear spin-lattice relaxation linear at 4.2<T<200 K and that of the electric resistivity (30<T<200 K) prove the metallic character of the conductivity of domeykite. The enhancement of nuclear relaxation, the narrowing of copper and arsenic NQR line widths are considered as arising due to the ionic movement starting beyond 200 K. This movement influences the electric resistivity, most likely due to the inreasing density of states at the Fermi surface.