Line shape analysis in nuclear quadrupole resonance spectroscopy (I=3/2)

Following the treatment of Vega (1973), the theoretical expressions for the second moments in nuclear quadrupole resonance (nqr) due to dipole-dipole interactions have been derived for the system containing the nuclei with spinI=3/2. Cases with the orientation of the static magnetic field and the interactions with the other magnetic nuclei are also dealt with.     

Hyperfine interactions of iron in ternary alloys with B82 type structures

The recoilless absorption spectra of iron in the ternary alloys CoFeGe, CoFeSb and FeMnGe, which possess B8₂ type structure, reveal the existence of different ordering temperatures of moments at 2(a) and 2(d) sites. Using the Einstein model to describe the second order Doppler shift, it has been found thatΘ _E appropriate to the thermal motions of iron atoms at 2(a) and 2(d) sites in CoFeGe are different, which is also suggested by the temperature dependences of the relative areas of the corresponding component spectra. In CoFeSb, on the other hand, relative areas of the component spectra are independent of temperature, and give the relative distribution of iron at the inequivalent sites. A large difference in the isomer shifts of 2(a) and 2(d) site spectra indicates a larger number of d-electrons in the atomi configuration for 2(a) atoms. The isomer shift change is negative for 2(a) site nuclei and positive for 2(d) site nuclei with increase in temperature. The magnetic fields at 2(d) site nuclei in CoFeGe and CoFeSb alloys indicate that the moments of the parent atoms are not much different from the value in iron metal.     

Magnetic moments of even-even nuclei (systematics)

Conclusion Magnetic moments of almost all nuclei are independent of excitation energy and level parity.Coupled neutrons and protons appear to be grouped into dipoles. The doubly magic²⁰⁸Pb nucleus and the neighbouring ones are found to be most complicated, for calculations, since their level magnetic structure is very unstable.Magnetic moments of all even-even nuclei known up to now may be described uniformly.It is necessary to introduce the effective magnetic moments (g-factors) for both protons and neutrons for a certain nucleus individually but according to uniform approach. These effective values are produced by all nucleons of a nucleus.It is possible to speak about transient properties of nuclei if there is a mutual compensation of the proton and neutron effectiveg-factors.The described method — from the experimental regularities via consideration of separate factors with the help of diagrams over the whole region of nuclei — is very convenient for distinguishing new regularities.     

Conformational and dielectric analysis of hydrogen bonded polar binary mixtures of propan-1-ol with propionaldehyde

The dielectric behaviour of polar liquids such as propan-1-ol, propionaldehyde and their equimolar binary mixture in non-polar solvent benzene is studied in the microwave frequency range using the cavity perturbation technique at 6.218 GHz (J band), 9.880 GHz (X band), 16.331 GHz (P band) and 24.951 GHz (K band). Ab initio geometry optimization is performed in the 6-31G (d) basis set using the Gaussian 94W program for both pure and binary systems of propan-1-ol and propionaldehyde. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the ab initio results. Conformational analysis of the formation of hydrogen bond between the propan-1-ol and propionaldehyde is supported by the FT-IR spectra. The average relaxation times are calculated from their respective Cole–Cole plots.     

Dynamic rotational characteristics of actinides on empirical approach

In the paper calculation of the moments of inertia for nuclei from the region 87 ≤ Z ≤ 100 and 130 ≤ N ≤ 156 was made in dependence on the angular momentum of their rotational states. The experimental values of the moments of inertia were calculated for rotational energy of the classic rotor in its quantum form, with the use of a simple formula. The moment of inertia term appearing in the formula was treated as a variable. The calculations were carried out on the basis of experimental data for the energies of the rotational levels for 51 bands built on ground states for even-even nuclei and for nuclei with odd mass number A. In addition, 30 rotational bands built on excited states were also analysed in the investigated region in case of even-even nuclei. For many bands and nuclei the considered dependence of the moment of inertia on angular momentum has been found in the analytical form by fitting polynomials to the experimental data. It turned out that obtained results for the moments of inertia made it possible to describe the energies of rotational levels with a relative deviation not greater or only slightly greater than 1%. In general, in the case of 12 bands of ground level the maximum relative deviation of obtained level energies is smaller than 1%.      

Magnetic moment predictions of odd-A nuclei with the Bayesian neural network approach

The Bayesian neural network approach has been employed to improve the nuclear magnetic moment predictions of odd-A nuclei. The Schmidt magnetic moment obtained from the extreme single-particle shell model makes large root-mean-square (rms) deviations from data, i.e., 0.949 \begin{document}$ \mu_\mathrm{N} $\end{document} and 1.272 \begin{document}$ \mu_\mathrm{N} $\end{document} for odd-neutron nuclei and odd-proton nuclei, respectively. By including the dependence of the nuclear spin and Schmidt magnetic moment, the machine-learning approach precisely describes the magnetic moments of odd-A nuclei with rms deviations of 0.036 \begin{document}$ \mu_\mathrm{N} $\end{document} for odd-neutron nuclei and 0.061 \begin{document}$ \mu_\mathrm{N} $\end{document} for odd-proton nuclei. Furthermore, the evolution of magnetic moments along isotopic chains, including the staggering and sudden jump trend, which are difficult to describe using nuclear models, have been well reproduced by the Bayesian neural network (BNN) approach. The magnetic moments of doubly closed-shell \begin{document}$ \pm1 $\end{document} nuclei, for example, isoscalar and isovector magnetic moments, have been well studied and compared with the corresponding non-relativistic and relativistic calculations.     

Electronic structure and magnetism of R(Fe,Si)12 (R = Y, Nd)

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)₁₂ compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic moments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total magnetic moments of RFe₁₀Si₂ (R = Y, Nd) are larger than those of RFe₁₀ M ₂ (M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the magnetic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduction of Si atoms according to spin fluctuation of DOS at Fermi level.     

Deformation constrained relativistic mean-field approach with fixed configuration and time-odd component

Deformation constrained relativistic mean-field (RMF) approach with fixed configuration and timeodd component has been developed and applied to investigate magnetic moments of light nuclei near doublyclosed shells. Taking 17O as an example, the results and discussion are given in detail.     

Deformation constrained relativistic mean-field approach with fixed configuration and time-odd component

Deformation constrained relativistic mean-field (RMF) approach with fixed configuration and time-odd component has been developed and applied to investigate magnetic moments of light nuclei near doubly-closed shells. Taking ¹⁷O as an example, the results and discussion are given in detail.     

NMR frequency and magnetic dipole moment of (3)He nucleus

We present new gas-phase NMR spectra which relate the resonance frequency of (3)He nucleus to the resonance frequency of the proton in tetramethylsilane (TMS). We discuss the dependence of (3)He resonance frequency on the density of the solvent gas, and we consider in detail the absolute shielding scales of both nuclei. Finally, we analyse the accuracy of the results, using the relationship between the resonance frequencies, absolute shielding constants and magnetic dipole moments of (1)H and (3)He nuclei.     

用BCS理论计算稀土核转动惯量的奇偶差

用BCS理论计算了稀土区偶偶核和奇A核的转动惯量.计算结果表明,尽管转动惯量的计算值系统地小于实验值,但实验上观测到的转动惯量奇偶差的大幅度变化能够用BCS理论定性地描述. 这个结论与人们普遍认为的BCS理论给出的奇A核转动惯量应比相邻的偶偶核基态转动惯量大15%的看法相悖,但却证实了20多年以前Gregory和Volkov等人得出的结论,有助于人们在BCS平均场理论框架下理解正常形变核中出现全同带的现象.     

Magnetic dipole moments of collective quadrupole excited states

Magnetic dipole moments for low-lying collective quadrupole excitations are studied in heavy and medium-heavy nuclei within the framework of the Interacting Boson Model (IBM-2). In the present study, we concentrate mainly on the fully symmetric representations of the U(6) group and their magnetic dipole moments. We shortly discuss the lowest non-symmetric 1⁺ level. Comparison with other collective model calculations of g_R and microscopic studies as well as with experimental data is performed.The authors are most grateful to A.E.L.Dieperink and coworkers for the generous help and permission to quote largely from their recent results on magnetic dipole moments in nuclei.They are also indebted to A.Richter,O.Scholten and Iachello for many stimulating discussions. They thank the NFWO,IIKW and the IWONL for financial support.     

Spectral line shapes of collision-induced light scattering (CILS) and collision-induced absorption (CIA) using isotropic intermolecular potential for H2–Ar

Quantum mechanical line shapes of collision-induced light scattering at room temperature (295 K) and collision-induced absorption at T = 195 K are computed for gaseous mixtures of molecular hydrogen and argon using theoretical values for pair-polarisability trace and anisotropy and induced dipole moments as input. Comparison with other theoretical spectra of isotropic and anisotropic light scattering and measured spectra of absorption shows satisfactory agreement, for which the uncertainty in measurement of its spectral moments is seen to be large. Ab initio models of the trace and anisotropy polarisability which reproduce the recent spectra of scattering are given. Empirical model of the dipole moment which reproduce the experimental spectra and the first three spectral moments more closely than the fundamental theory are also given. Good agreement between computed and/or experimental line shapes of both absorption and scattering is obtained when the potential model which is constructed from the transport and thermo-physical properties is used.     

铯原子里德堡态Stark能量及电偶极矩的测量和理论计算

里德堡原子由于具有体积大、寿命长、易极化及在外电场中能级易于操控等特点, 已经成为了目前物理学领域研究的热点之一. 本文在磁光阱中实验测量了铯原子15P_3/2和16P_3/2态的Stark光谱,根据光谱给出了15P_3/2和16P_3/2|m|=1/2 Stark态在0-1400 V/cm场强范围适用的Stark 能量和偶极矩的经验性解析表达式; 用数值方法求解薛定谔方程获得了这些态的Stark能量、偶极矩和电子几率密度分布. 电子几率密度分布定性说明了计算的偶极矩矢量的方向是正确的. 计算的Stark能量、偶极矩与实验结果相一致.     

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.     

The moment method for boundary layer problems in Brownian motion theory

We apply Grad's moment method, with Hermite moments and Marshak-type boundary conditions, to several boundary layer problems for the Klein-Kramers equation, the kinetic equation for noninteracting Brownian particles, and study its convergence properties as the number of moments is increased. The errors in various quantities of physical interest decrease asymptotically as inverse powers of this number; the exponent is roughly three times as large as in an earlier variational method, based on an expansion in the exact boundary layer eigenfunctions. For the case of a fully absorbing wall (the Milne problem) we obtain full agreement with the recent exact solution of Marshall and Watson; the relevant slip coefficient, the Milne length, is reproduced with an accuracy better than 10^–6. We also consider partially absorbing walls, with specular or diffuse reflection of nonabsorbed particles. In the latter case we allow for a temperature difference between the wall and the medium in which the particles move. There is noa priori reason why our method should work only for Brownian dynamics; one may hope to extend it to a broad class of linear transport equations. As a first test, we looked at the Milne problem for the BGK equation. In spite of the completely different analytic structure of the boundary layer eigenfunctions, the agreement with the exact solution is almost as good as for the Klein-Kramers equation.     

Effective charges for 88Sr and 90Zr closed-shell cores

Effective charges are calculated for protons and neutrons in the region of mass 90. It is found that their magnitudes differ appreciably depending on whether the proton p _1/2 shell is empty or full. The calculated values are compared with values deduced from nuclei with simple configurations, and from a fit to N=50 data. The empirical values are used in shell-model calculations of quadrupole moments of N=50-58 nuclei. Received: 16 February 1998     

The systematics of (n, α) reaction cross-sections at 14.5 MeV neutron energy

A comprehensive review of the experimental data for 14.5 MeV neutron induced reaction crosssections for (n, α) reaction has been made for the isotopes having Z up to 82. Two different parameter groups have been considered by the classification of nuclei into odd-mass and even-even nuclei. The empirical formulae with two parameters for the evaluation of (n, α) reaction cross-sections are discussed in the present study. The odd-even effects have been observed as the cross-sections of odd-mass nuclei are higher as compared to their neighboring even-even nuclei. The shell effects have also been established at magic nucleon numbers for these reaction cross-sections.     

Description of the Superdeformed Bands of the Odd-Odd Nuclei in A～150 Region

With the supersymmetry scheme including many-body interactions, the global property and the ΔI=4 bifurcation in the superdeformed (SD) bands of odd-odd nuclei in A～150 mass region are investigated systematically. Good results for the γ-ray energies, the dynamical moments of inertia, and energy differences ΔE_γ-ΔE_γ^ref are obtained. It shows that this approach is quite powerful in describing not only the SD bands in even-even and odd-A nuclei but also those in odd-odd nuclei in the mass region.     

Moment Systems Derived from Relativistic Kinetic Equations

In this paper, we are interested in the derivation of macroscopic equations from kinetic ones using a moment method in a relativistic framework. More precisely, we establish the general form of moments that are compatible with the Lorentz invariance and derive a hierarchy of relativistic moment systems from a Boltzmann kinetic equation. The proof is based on the representation theory of Lie algebras. We then extend this derivation to the classical case and general families of moments that obey the Galilean invariance are also constructed. It is remarkable that the set of formal classical limits of the so-obtained relativistic moment systems is not identical to the set of classical moments quoted in Ref. 21 and one could use a new physically relevant criterion to derive suitable moment systems in the classical case. Finally, the ultra-relativistic limit is considered.