Review of Induced Gamma Emission and Gamma-Ray Laser Research

Induced gamma emission with the potential for substantial energy gain is an exciting area of research. This paper reviews related work done internationally, including some that has potential for a gamma-ray laser. This revised version was published online in August 2006 with corrections to the Cover Date.     

Non-Radiative Triggering of Long-Lived Nuclear Isomers

The triggering of long-lived isomeric nuclei by non-radiative excitation to a relatively short-lived mediating state is considered. Coulomb triggering in inelastic scattering of heavy ions, a transfer of triggering energy from resonant electron transitions of atomic shell (NEET) and triggering by capture of a free electron into a bound atomic state (NEEC) are discussed. Cross sections for the above processes of non-radiative triggering are presented and the relative efficiencies of these different triggering mechanisms are discussed. Numerical estimates are presented for the selected isomers. This revised version was published online in August 2006 with corrections to the Cover Date.     

利用双色激光感生光栅光谱法测定^127I的核自旋

本文利用ＮｄＹＡＧ激光倍频光５３２ｎｍ激光分成强度大致相等的两束激光作为泵浦光以２．７３°交叉于碘分子样品室中，两束泵浦光发生干涉在碘分子中选择激发形成了空间正弦分布的激光态分子光栅和基态耗尽型光栅。另一束窄线宽染料激光作为探索光射入到激光感生光栅上，沿着布拉格衍射的方向接收信号光。利用泵浦共振为３２－０Ｒ（５５），探索共振为１３－０Ｐ（５５），Ｒ（５５）和泵浦共振为３２－０Ｐ（５２），探索共振为１３－０Ｐ（５２），Ｒ（５２）的碘分子双色激光感生光栅光谱谱线强度测定了１２７Ｉ的核自旋，测定值为５／２。     

Exotic Isomers in Deformed Atomic Nuclei

Excited states of atomic nuclei can have long half lives, due to the angular-momentum couplings of unpaired nucleons. Such isomeric states provide opportunities for exploring novel nuclear physics, astrophysics and physics at the atomic/nuclear interface. This review focuses on the properties of isomers in deformed nuclei, and emphasises the importance of axial symmetry in preserving the integrity of the K quantum number. A region of neutron-rich nuclei around ¹⁸⁸Hf (Z=72, N=116) is predicted to have exceptional isomer properties, and experimental advances are now opening up this region to detailed investigation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nuclear Spin Maser Oscillation of 129Xe by Means of Optical-Detection Feedback

We have developed the nuclear spin maser oscillating at a low frequency of 34 Hz with highly polarized nuclear spins of the noble gas element ¹²⁹Xe. The system is advantageous for detecting a small frequency shift of the nuclear spin precession. We are thus planning to apply this system to the search for an atomic electric dipole moment of ¹²⁹Xe. We here report the development of the system and its performance.     

Nuclear Spin Alignment of 12,13B Produced in Heavy Ion Collisions

The nuclear spin alignments of the β-emitting fragments ¹²B(I ^π=1⁺, T _1/2=20.2 ms) and ¹³B(I ^π=3/2⁻, T _1/2=17.4 ms) produced in the 100A-MeV ¹³C, ¹⁵N + ⁹Be collisions respectively have been observed for the first time detecting asymmetric β-ray emission from these nuclei. By means of the spin manipulation technique based on the hyperfine interaction of B isotopes in TiO₂, both the polarization P and the alignment A were determined reliably. The obtained P and A were significantly smaller than the expectation from the kinematical model. From the fact that the quenching factors for P and A are almost the same, there may be some depolarization mechanism in the collision process itself. This revised version was published online in September 2006 with corrections to the Cover Date.     

Nuclear Spin Alignment and Alignment Correlation Terms in Mass A = 8 System

The pure nuclear spin alignments of ⁸Li and ⁸B were produced from the nuclear spin polarization applying the β-NMR method. The alignment correlation terms in the β-ray angular distribution were observed to test the G parity conservation in the nuclear β decay.     

The Gamma Resonance Problem of Long-Lived Nuclear Isomers

A review is given of the studies relating to the problem of γ-resonant (Mössbauer) excitation of long-lived nuclear isomers. The theoretical estimates of possible γ-line broadening are presented. Earlier experiments are described with ^107mAg and ^109mAg isomers using polycrystalline samples of pure Ag and Ag-Pd alloys. The results of these experiments did not contradict the theoretical predictions. The series of papers using Ag single-crystal γ-sources is reviewed. Their results were interpreted as indications of a rather small ^109mAg γ-line broadening, which cannot be explained by modern theory. The results of the last experiments by ITEP group with ^109mAg are also presented. These data may be coordinated with results of other research, if one takes into account the Zeeman splitting of the γ-spectra by Earth's magnetic field.     

Search for γ-Emission from Isomeric Nuclei Induced by MeV Electron Beams

In this paper we study the nuclear transitions induced by incident electrons having an energy of several MeV's. We measured the cross sections for the excitation of isomeric nuclear states by 7.7 MeV electrons. The cross sections were 1.2 μb for ^111m Cd, 5.5 μb for ^113m In and 7.0 μb for ^115m In. The peak activation rates were 1.8×10⁻¹² s⁻¹ for ^111m Cd, 8.1×10⁻¹² s⁻¹ for ^113m In and 1.0×10⁻¹¹ s⁻¹ for ^115m In, for a peak power of the electron beam of 1.8×10⁶ W cm⁻². Then we describe for the first time the results of a series of experiments in which samples containing the isomeric nuclei ^166m Ho and ^186m Re have been irradiated with MeV electron beams. An upper limit of 17 mb has been determined for the cross section of electron-induced γ-emission from ^166m Ho and an upper limit of 2.2 mb has been determined for the cross section of electron-induced γ-emission from ^186m Re. This revised version was published online in July 2006 with corrections to the Cover Date.     

高能诱发核反应中粒子产生的相对信息熵

在本实验中，引用了一个新的特征量，相对信息熵Ｒ，研究了能量为１４．６，６０，２００ＡＧｅＶ的氧离子和２００ＡＧｅＶ的硫离子诱发核反应的产生粒子多重数分布．在目前的能区中，Ｒ近似地能量无关．Ｒ对快度窗口大小依赖的饱和性，揭示了中心区的熵集中产生．实验结果与Ｌｕｎｄ模型的ＦＲＩＴＩＯＦ模拟计算的预言一致．     

NMR Nomenclature: Nuclear Spin Properties and Conventions for Chemical Shifts. IUPAC Recommendations 2001

A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the ¹H resonance of tetramethylsilane. The unified scale is designed to provide a precise ratio, Ξ, of the resonance frequency of a given nuclide to that of the primary reference, the ¹H resonance of tetramethylsilane (TMS) in dilute solution (volume fraction, <1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements. Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ, is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made. Standardised nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with non-zero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios, and receptivities, together with quadrupole moments and line-width factors (where appropriate).     

Effects of N/Z on Spin Distribution of Evaporation Residue Cross Section as a Probe of Nuclear Dissipation

The spin distribution of the evaporation residue cross section of nuclei ^194pb, ^200Pb, ^206Pb, and ^200 Os are calculated via a Langevin equation coupled with a statistical decay model. It is shown that with increasing the neutronto-proton ratio （N/Z） of the system, the sensitivity of the significantly. Moreover, for ^200Os this spin distribution is no spin distribution to the nuclear dissipation is decreased longer sensitive to the nuclear dissipation. These results suggest that to obtain a more accurate pre-saddle viscosity coefficient through the measurement of the evaporation residue spin distribution, it is best to yield those compound systems with low N/Z.     

Cascade of Magnetic Field Induced Spin Transitions in LaCoO_{3}

We present magnetization and magnetostriction studies of LaCoO_{3} in magnetic fields approaching 100?T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co^{3+} ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co^{3+} ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.     

Gamma Spectroscopy of Hf-178m2 Using Synchrotron X-Rays

Preliminary survey experiments have been performed to examine the triggering of gamma emission from the 31-year Hf-178m2 isomer using intense monochromatic synchrotron radiation from the X15A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. Initial studies were performed to probe incident photon energies over the L ₁, L ₂, and L ₃ X-ray edges of Hf and the 12–13 keV range. Resonances larger than the experimental minimum detectable level of 10⁻²⁵ cm² keV were not observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of the Mechanism of Photolysis of Methanol-d4 Solutions of Acetylpropionyl Peroxide with the Use of Chemically Induced Dynamic Nuclear Polarization

On the basis of the effects of chemically induced dynamic nuclear polarization of ¹H and ¹³C and the yields of reaction products, the photolysis of methanol-d₄ solutions of acetylpropionyl peroxide is investigated within the temperature interval 193–333 K. Polarization of all the protons of ethylethanoate is detected; it is shown that the latter is formed in several chemical reactions. The role of different excited states of the peroxide in the mechanism of its photolysis is discussed.     

Spin dynamics in magnetic materials investigated by muon spin relaxation

We present a quantitative analysis of the temperature dependence of the muon spin relaxation rate measured in simple magnets. We consider the low temperature, critical and high temperature regimes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Probing Shell Correction at High Spin by Neutron Emission of Doubly Magic Nuclei 208pb and 132Sn

Shell effects in particle emission for two doubly magic nuclei 132 Sn and 208 Pb were studied in the framework of Smoluchowski equation taking into account temperature and spin-dependent shell correction. It is shown that the shell effects in the enission of pre-scission neutrons are sensitive to the spin dependence of the shell correction at a moderate excitation energy. Therefore, we propose to use neutron multiplicity as an observable to probe the shell correction at high spins.     

Laser-Mössbauer Spectroscopy as a New Tool for Nuclear Transitions

New spectroscopic technique based on modification of Mössbauer spectra via optical coherent driving of atomic transitions is suggested. Possible experimental realizations are discussed.     

Electron Spin–Nuclear Spin Cross-Correlation Effects on Multiplet Splittings in Paramagnetic Proteins

The effects of cross-correlation between Curie spin–nuclear dipole and nuclear dipole–nuclear dipole interactions on the linewidths and resonance frequencies of the individual lines of anAXmultiplet in paramagnetic systems have been calculated. The implication of the relaxation-induced frequency shift of the lines (dynamic frequency shift) for the accurate measurement of residual dipolar couplings in field-oriented systems has been discussed. Our simulations indicate that these effects may play a role in the precise measurement of residual dipolar couplings in systems which belong to the small and intermediate tumbling regime, i.e., correlation times less than 5 ns.     

纳米管中的自旋极化

结构缺陷、掺杂等可以导致纳米管的自旋极化，而自旋极化的纳米管可以利用载流子的自旋状态作为信息载体，实现一维的自旋电子传输。具有不同自旋极化结构的纳米管，根据其电子结构、自旋极化性质和输运性质的不同，可以用于实现不同用途的自旋电子器件。很多有关自旋极化的纳米管的理论和实验工作已经展开，然而其中仍有很多物理问题有待深入研究。