Double resonance NMR/ON of185IrNi and188IrFe

In order to establish small quadrupole splittings the double resonance NMR/ON method was applied to¹⁸⁵IrNi and¹⁸⁸IrFe at 7 and 8.6 mK, respectively. With r.f. power applied at the strongest resonance frequency, a second frequency was used to simultaneously investigate the second resonance component, where the splitting is caused by an electric quadrupole interaction. Enhanced quadrupole subresonances were observed. In these experiments we have demonstrated the powerful capability of the double resonance NMR/ON method to observe a small quadrupole interaction when the resulting subresonances are well resolved.     

Low temperature nuclear orientation and its application to magnetic systems

This article contains an outline of the basic principles of low temperature nuclear orientation LTNO and of nuclear magnetic resonance on oriented nuclei NMR/ON. A summary is given of the experimental requirements and constraints of these methods followed by a survey of their applications to the study of magnetism in solids. More detailed consideration is given to relaxation topics, including fast passage and pulsed RF techniques, and to the variety of methods now available, based on nuclear orientation and resonance, for the separate extraction of magnetic dipole and electric quadrupole interaction strengths when they occur together.     

The extraction of weak nuclear electric quadrupole splittings of dilute impurities in ferromagnets using modulated Adiabatic Passage NMR/ON

A novel extension of the Single or Adiabatic Fast Passage NMR/ON technique is described. Its principal advantages in extracting the mode magnitudes and distribution widths of weak nuclear electric quadrupole splittings much less than the magnetic inhomogeneous broadening are its simplicity and generality requiring no assumptions on the degree of adiabaticity of the nuclear spin motion during sweep through the quadrupolar split subresonances. The technique is applied to a concentrated single crystal sample of⁶⁰CoFe which failed to yield a well resolved mid passage signal to conventional single passage NMR/ON. The result is an asymmetric frequency distribution of quadrupole frequencies with a mode value of P=3e²qQ/4I (2I-1)=+4.5 ±1.0 kHz and half maxima of +2.5 kHz and +7.0 kHz.     

Nuclear spin-lattice relaxation in ferromagnetic amorphous alloys Fe81Co3B16 andFe70Co10B20 measured by NMR and Nuclear orientation

The nuclear spin-lattice relaxation of⁵⁹Co in amorphous Fe-Co-B alloys was studied by NMR andthe results were compared with nuclear orientation measurements. The NMR relaxation rates were evaluated taking into account the electric quadrupole interaction. Then the results of both methods are in good agreement. It was confirmed that the spin-lattice relaxation is independent of the external magnetic field in the magnetically saturated samples andit was found that it does not depend on Co concentration.     

Irreducible spin precession theory applied to some topics in atomic and nuclear radio-frequency spectroscopy

Several problems from radio-frequency spectroscopy of atoms and nuclei are treated with irreducible spin precession theory. In the first part, effective field techniques are used to derive analytically single and multiple quantum double resonance lineshapes for atoms with a hyperfine structure in a high magnetic field. In the second part (as an extension to previous work), nuclear resonance signals are calculated for oriented nuclei subject to an electric hexadecapole interaction. Lineshapes of acoustically driven hexadecapole transitions are derived in closed form and compared to experiment. Further, multiple quantum NMR transitions within a hexadecapole shifted nuclear Zeeman structure are calculated, and some distinct features of hexadecapole effects on NMR lineshapes are pointed out. This last case is of current interest due to recent progress in NMR-line narrowing techniques. — In the Appendix, we give lineshape equations for single and double quantum NMR transitions on oriented (I=1)-nuclei subject to an electric quadrupole interaction; these equations are also being used in the atomic rf-spectroscopy calculations. The equations are exact to all orders of the interaction with the external fields.     

Site-selective electron nuclear double resonance in the exchange-narrowed regime of the ESR in conducting solids

Electron nuclear magnetic double resonance on conduction electrons reveals the hyperfine interaction hidden by the fast electron spin exchange. We used the Overhauser shift technique to investigate the electron spin density of the conduction band of gallium oxide, beta-Ga(2)O(3). Due to the monoclinic structure, the conduction band of beta-Ga(2)O(3) is anisotropic and it is dominated by contributions from the two nonequivalent Ga sites. The large quadrupole couplings of the two gallium isotopes (69)Ga and (71)Ga (both with I = 3/2) are completely resolved in our double-resonance experiments. This resolved quadrupole interaction allows the determination of the electric field gradients at both gallium sites with high precision and high sensitivity. The resolved quadrupole splitting is the key to the site-selected determination of the hyperfine interaction. The concepts behind these double-resonance techniques are rather general and should be applicable in similar semiconductor systems.     

Numerical solutions for single passage NMR on nuclei experiencing small electric quadrupole interactions

The adiabatic rapid-passage NMR equations are numerically solved for a small additional quadrupole interaction. The full range of the ratio of rf interaction strengths to quadrupole interactions strengths is considered for any electric field gradient orientation. The results forI=1 are particularly easy to describe and are used to predict the single-passage results for different orientations of the electric field gradient with respect to the static magnetic field.     

14N chemical shifts and quadrupole coupling constants of inorganic nitrates

The isotropic chemical shift and the nuclear quadrupole coupling constant for (14)N were obtained for 14 inorganic nitrates by solid-state MAS NMR measurements at two different field strengths, 9.4 and 11.7 T. The compounds studied were polycrystalline powders of AgNO(3), Al(NO(3))(3), Ba(NO(3))(2), Ca(NO(3))(2), CsNO(3), KNO(3), LiNO(3), Mg(NO(3))(2), NaNO(3), Pb(NO(3))(2), RbNO(3), Sr(NO(3))(2), Th(NO(3))(4)center dot4H(2)O, and UO(2)(NO(3))(2)center dot3H(2)O. Even though the spectra show broadening due to (14)N quadrupole interactions, linewidths of a few hundred hertz and a good signal-to-noise ratio were achieved. From the position of the central peaks at the two fields, the chemical shifts and the nuclear quadrupole coupling constants were calculated. The chemical shifts for all compounds studied range from 282 to 342 ppm with respect to NH(4)Cl. The nuclear quadrupole coupling constants range from 429 kHz for AgNO(3) to 993 kHz for LiNO(3). These data are compared with those available in the literature.     

Ab initio study of the EFG at the N sites in imidazole

We study the nuclear quadrupole interaction at the nitrogen sites in the molecular and crystalline phases of the imidazole compound. We use PAW which is a state-of-the-art method to calculate the electronic structure and electric field gradient at the nucleus in the framework of the density functional theory. The quadrupole frequencies at both imino and amino N sites are in excellent agreement with measurements. This is the first time that the electric field gradient at crystalline imidazole is correctly treated by an ab initio theoretical approach.     

Electric quadrupole interactions measured by nuclear orientation and NMR on oriented nuclei

A review is given of the situations in which low temperature nuclear orientation and NMR of oriented nuclei have been applied in recent years to the measurement of electric quadrupole interactions in metals and in dielectric crystals. The review is concerned with the variety of methods by which quadrupole interactions have been measured. Illustrative examples are given for each technique, but no attempt is made to give a full bibliography of work. As regards nuclear orientation, pure quadrupole algnment is discussed (although in non-cubic metals rather than in dielectric crystals), followed by outlines of work on mixed magnetic dipole and electric quadrupole hfi when these interactions are (a) co-axial and (b) mutually perpendicular. The sensitivity of nuclear orientation to small quadrupole interactions is shown to be improved in the second case.For NMR on oriented nuclei the review centres upon the small quadrupole effects detected in dilute ferromagnetic alloys both by direct observation of resonance line structure and by interpretation of signals following adiabatic fast passage.Republished from the XVIIth Winter School on Physics (Hyperfine Interactions) held from February 19-March 3, 1979 in Bielsko Biala (Poland), with the kind permission of the Editors.     

Magnetic hyperfine field at caesium in iron

We report temperature dependence of nuclear orientation (NO), and the first observation of NMR/ON on Cs in iron.^{132, 136}Cs were implanted at room temperature into polycrystalline and single crystal iron. NO values for the (average) magnetic hyperfine field B_hf (CsFe) are close to 34T, intermediate between the value of 40.7T found in on-line samples made at mK temperatures and the NMR/ON value of 27.8 (2)T. The latter studies. The site/field distribution is briefly discussed. ISOLDE Collaboration, CERN     

Quadrupole moment of the doubly closed shell +1 nucleon nucleus41Sc(Iπ=7/2−)

The nuclear electric quadrupole moment of⁴¹Sc(I^π=7/2⁻) was experimentally determined by use of the NMR detection in which the asymmetric β-ray distribution from spin polarized nuclei was monitored. The magnetic interaction of the state with high external magnetic field and the nuclear quadrupole interaction with the electric field gradient obtained in TiO₂ crystal were studied. The field gradient seen to the implanted⁴¹Sc was measured independently by the high field NMR detection on the stable isotope⁴⁵Sc located in the equivalent⁴¹Sc site with. |Q(⁴¹Sc;I^π=7/2⁻)|=(0.120±0.006) b was determined.     

Nuclear level mixing resonances on low temperature oriented nuclei

The angular distribution of gamma radiation emitted from oriented nuclei can show resonance signals under the influence of combined magnetic and electric quadrupole interactions acting as an intermediate state perturbation. An exploratory experiment shows the feasibility of this method. Perspectives of using these level mixing resonances on oriented nuclei (LMR/ON) are also discussed.     

Optical polarization of neutron-rich sodium isotopes and β-NMR measurements of quadrupole moments

The nuclear quadrupole moments of neutron-rich sodium isotopes are being investigated with the help of in-beam polarization by optical pumping in combination with-NMR techniques. First measurements have yielded the quadrupole splittings of NMR signals in the lattice of LiNbO₃ for the isotopes²⁶Na,²⁷Na and²⁸Na. Interaction constants and ratios of the electric quadrupole moments are derived. In view of future experiments,-decay asymmetries for the sequence of isotopes up to theN=20 neutron shell closure,^26–31Na, have been measured.     

The temperature dependence of quadrupole interactions at cadmium impurities in Arsenic metal

We have performed time differential perturbed angular correlation measurements over a temperature range from 77 K to 763 K to investigate the static electric quadrupole interaction of¹¹¹Cd in rhombohedral Arsenic metal. The observed quadrupole interaction frequency decreases with increasing temperature and is consistent with the well knownT ^3/2 relation, valid for metals.     

Recent developments and new trends in NMR on oriented nuclei

Recent developments in nuclear magnetic resonance on oriented nuclei (NMR-ON) are reviewed with the following main topics: (i) Measurement of magnetic moments. In this context the resonance shift of NMR-ON resonances with an external magnetic field is discussed critically. (ii) Resonance techniques for the measurement of electric quadrupole moments. It is shown that — with hcp-Co as host matrix — the techniques QI-NMR-ON (quadrupole-interaction-resolved NMR-ON) and MAPON (modulated adiabatic passage on oriented nuclei) have a tremendous potential for the measurement of quadrupole moments of radioactive nuclei. Data are presented for medium (Zr, Nb) and heavy elements (Ir, Pt, Au, Hg). With results on the 11/2^– isomers in Au it is shown that MAPON yields highly precise quadrupole moments of states with half-lives of the order of seconds, for which no other technique with comparable precision exists up to now. In the case of⁹⁰Nb it is demonstrated that MAPON allows also the measurement of very small quadrupole moments with high precision. (iii) Electric field gradients in cubic Fe, fcc-Co and Ni. MAPON experiments show a strong magnetic-field dependence of the effective quadrupole interaction; the implications are discussed. (iv)-decay-induced lattice site change identified by a double-resonance NMR-ON measurement. The resulting change of the hyperfme interaction has severe consequences for the interpretation of time-integral and even time-differential nuclear orientation measurements on nuclei far off stability. (v) Spin-lattice relaxation for nuclei on non-substitutional lattice sites. Recent experiments support the global character of the spin-lattice relaxation, in contrast to the local character of the static magnetic hyperfine interaction. (vi) Magnetic-field dependence of the spin-lattice relaxation. Recent experiments with hcp-Co as host lattice strongly support the so-called enhancement factor model and disfavour the one-, two- or three-magnon processes postulated in the literature.     

兰州彭宁阱核心电极的最优电压幅值计算

彭宁阱是用于直接测量原子核质量的精确设备。为了保证彭宁阱的测量精度,需在阱中心产生精准的四极静电场,而四极静电场是通过对彭宁阱的核心电极施加合适的电压产生的。采用公式推导法和最小二乘法两种方法计算得到了LPT核心电极需加电压幅值。对于公式推导法,电压值完全从理论出发,经公式推导后计算得到;最小二乘法的出发点是使取样偏差的平方和最小,且通过仿真模拟考虑了电极的实际几何形状。由这两种方法得到的非四极项系数C4 和C6,可用于估算因偏离理想四极电场所产生的实验误差。虽然这两种方法的出发点不同,但都可以在阱中心产生需要的四极电场。Penning trap mass spectrometry is one of the direct methods and maybe the most accurate tool for atomic mass measurements. The quadrupole electric eld produced in the trap should be very accurate in order to ensure the precision of measurements. The optimal amplitudes for the key electrodes of the Lanzhou Penning Trap(LPT) have been calculated by two methods|formula derivation and least-squares tting. For formula derivation method, the optimal values are based on the theory and deduced from the formulas. Least-squares tting method is to minimize the quadratic sum of sampling deviations, where the actual geometry of the electrodes has been considered by the simulation. The obtained C4 and C6 values can be used to estimate the experimental error produced by the deviation from the ideal quadrupole electric eld. The expected quadrupole electric led could be gotten by both methods.     

73Ge NMR spectra in germanium single crystals with different isotopic composition

We have studied the influence of isotopic disorder on the local deformations in Ge single crystals from both experimental and calculation points of view. The nuclear magnetic resonance (NMR) spectra of⁷³Ge nuclei (the nuclear spin equals 9/2) in perfect single crystals of germanium with different isotopic content were measured at temperatures 80, 300 and 450 K. Abnormal broadening of the spectrum was found to occur when the magnetic field was aligned along the [111] axis of a crystal. The observed specific angular dependence of the quadrupole broadening was attributed to isotopic disorder among atoms of germanium sited around the⁷³Ge NMR probe. Local lattice deformations in germanium crystal lattice due to isotopic impurity atoms were calculated in the framework of the adiabatic bond charge model. The results obtained were applied to study random noncubic crystal field interactions with the nuclear quadrupole moments and corresponding effects in NMR spectra. Simulated second and fourth moments of resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions agree qualitatively with the experimental data.