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1.
The alignment correlation term in the β-decay angular distribution from purely nuclear spin aligned 20Na has been measured for the first time. The final objective is to test the G parity symmetry, one of the fundamental symmetry in the weak nucleon current. For artificial creation of the alignment, the
knowledge of the hyperfine interaction of 20Na implanted in a single-crystal ZnO was utilized.
*Research Abroad, Japan Society for the Promotion of Science 相似文献
2.
M. Keim U. Georg A. Klein R. Neugart M. Neuroth S. Wilbert P. Lievens L. Vermeeren B. A. Brown 《The European Physical Journal A - Hadrons and Nuclei》2000,8(1):31-40
The nuclear electric quadrupole moments of the isotopes 26Na, 27Na, 28Na and 29Na were measured by -NMR spectroscopy in single crystals of LiNbO3 and NaNO3. High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear
laser beam. The polarized nuclei were implanted into the crystals and NMR signals were observed in the -decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of 27-31Na and confirmed the spin I=3/2 for 31Na. The results are discussed in comparison with large-basis shell model calculations.
Received: 1 February 2000 / Accepted: 3 April 2000 相似文献
3.
Jyoti K Parikh 《Pramana》1976,6(1):42-58
The energy levels of21, 23Na,22, 23Ne,24, 28Mg and25, 29Al are obtained by mixing various bands using the projected deformed Hartree-Fock (DHF) method. Solutions having minimum energies
are found to be prolate for all the nuclei considered here. Higher bands are obtained either by considering particle-hole
excitations or oblate solutions. These various bands are mixed using the projection method and care has been taken to orthogonalize
the bands. The interactions used in this study are those given by Kuo, Preedom-Wildenthal (PW) and WHMK interactions. The
last one seems to give good results for most of the nuclei considered here. Not only are the lowest bands well-reproduced
but the second lowest bands agree reasonably well in most nuclei. The third lowest ones obtained in some nuclei are not yet
observed as complete bands. However, K obtained for the third band seems to be correct. A comparison with shell model calculations—which
are numerically exhausting—shows similar results for the lowest band. However, the agreement of the second band varies from
nucleus to nucleus. A comparison between matrix elements of the interactions is made to analyze the results. 相似文献
4.
T. Pietraß R. Seydoux A. Pines 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,133(2):299-303
The surface proton spin polarization created by the spin-polarization-induced nuclear Overhauser effect from optically polarized xenon can be transferred in a subsequent step by solid-state cross polarization to another nuclear spin species such as29Si. The technique exploits the dipolar interactions of xenon nuclear spins with high γ nuclei such as1H, and is experimentally simpler than direct polarization transfer from129Xe to heteronuclei such as13C and29Si. 相似文献
5.
Abstract The optical properties of nominally pure and Er3+- or Pr3+ -doped yttria-stabilized zirconia single crystals were investigated under UV light excitation. In the excitation spectra of both types of doped crystals, a broad UV band is observed. Under excitation with light of different wavelengths inside this band, the luminescence features of the doped crystals are different. YSZ: Pr3+ samples exhibit the characteristic 4f → 4f emission of the Pr3+ ions. In YSZ: Er3+ crystals, both the Er3+ ion and the intrinsic luminescence are observed. Host to Er3+ ion radiative energy-transfer is also demonstrated. No dependence of the transfer process with the excitation wavelength was found. These results suggest that the UV band in Er3+ -doped crystals is associated with the lattice-dopant ion interaction rather than with the 4f5d interconfigurational band of the Er3? ions. 相似文献
6.
The nuclear quadrupole interaction of 204mPb in lead oxides has been measured by γ–γ time differential perturbed angular correlation. Ab-initio calculations of the electric field gradients and X-ray diffraction allowed the assignment of the detected nuclear quadrupole
interactions to the different Pb sites in the PbO phases litharge and massicote as well as in Pb3O4. The TDPAC probe 204mPb was produced with a 204Bi/204mPb-generator at the home laboratory at the University of Leipzig. The use of a high performance liquid chromatography system
increased significantly the yield, the specific activity of 204mPb, and reduced the acidic concentration of the eluate. 相似文献
7.
Mark Augath Patrick Heiler Stefan Kirsch Lothar R. Schad 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):134-136
The maintenance of a gradient of potassium and sodium ions across the cell membranes is essential for the physiological function of the mammal organism. The measurement of the spatial distribution of pathologically changing ion concentrations of 23Na and 39K with magnetic resonance imaging offers a promising approach in clinical diagnostics to measure tissue viability. Existing studies were focused mainly on 23Na imaging as well as spectroscopy with only one post-mortem study for 39K imaging. In this paper a triple resonant RF coil setup for the rat head at 9.4 T is presented for imaging of both nuclei (23Na and 39K) and the acquisition of anatomical proton images in the same experiment without moving the subject or the RF coil. In vivo MR images of 39K and 23Na in the rat brain were acquired as well as anatomical proton images in the same scanning session. 相似文献
8.
M. Assié F. de Oliveira Santos T. Davinson F. de Grancey L. Achouri J. Alcántara-Núñez T. Al Kalanee J.-C. Angélique C. Borcea R. Borcea L. Caceres I. Celikovic V. Chudoba D.Y. Pang C. Ducoin M. Fallot O. Kamalou J. Kiener Y. Lam A. Lefebvre-Schuhl G. Lotay J. Mrazek L. Perrot A.M. Sánchez-Benítez F. Rotaru M.-G. Saint-Laurent Yu. Sobolev N. Smirnova M. Stanoiu I. Stefan K. Subotic P. Ujic R. Wolski P.J. Woods 《Physics letters. [Part B]》2012
The unbound nucleus 18Na, the intermediate nucleus in the two-proton radioactivity of 19Mg, was studied by the measurement of the resonant elastic scattering reaction H(17Ne,p)17Ne performed at 4 A.MeV using a radioactive beam from the SPIRAL Facility. Spectroscopic properties of the low-lying states were obtained in an R-matrix analysis of the excitation function. 相似文献
9.
The alkaline-earth fluorohalide crystals MFX, where M=Ca, Sr, Ba, Pb and X=Cl, Br, I, form an important class of materials crystallizing in the PbFCl-type tetragonal structure which is also called the matlockite structure. These compounds have long been of interest because of the various defect species which can be detected by spin resonance and associated techniques. The crystals were prepared by slow cooling of the melt of a stoichiometric mixture of BaF 2 and the corresponding chloride or bromide under 0.2 bar of ultrapure argon (5N5), often slightly fluorinated. We have studied the mechanoluminescence (ML) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals. It is seen that after the impact of a moving piston, initially the ML intensity increases with time, attains a maximum value and then it decreases with time up to a particular minimum value, and then it increases again, attaining a peak value and finally disappears. The first peak lies in the deformation region and the second peak lies in the post-deformation region. The ML intensity of the BaFCl:Sm 2+ crystal is much higher than the ML intensity of the BaFBr:Sm 2+ crystal. For different impact velocities, the ML intensity increases with velocity; and the total ML intensity attains a saturation value for higher impact velocities. The total ML intensity increases with the increase in the applied load. It is suggested that the moving dislocation produced during deformation of crystals captures holes from hole-trapped centers (like H centers), and the subsequent radiative recombination of the dislocation holes with electron gives rise to ML. Thermoluminescence (TL) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals was studied after exposure to ultraviolet rays with the help of a TLD reader. The peak of TL for the BaFBr:Sm 2+ crystal is found at ~247°C and for BaFCl:Sm 2+ crystals at 283°C. The TL intensity initially increases with increase in the UV radiation and then it attains saturation for higher values of UV exposure. The absorption spectrum was recorded with the help of a UV–visible spectrophotometer (Shimadzu). The band found at 275 nm was attributed to H centers. 相似文献
10.
We have investigated the photoluminescence (PL) and photostimulated luminescence (PSL) spectra at 300 K to study the effect
of isoelectronic impurities K+ and I− on the formation and energy structure of Eu2+-VCs isolated dipole centers and aggregate centers in the form of single crystals of CsEuBr3 in CsBr:Eu2+ single crystals. We have shown that K+ and I− impurities in a concentration of 5 mol% do not have a substantial effect on the energy spectrum of isolated dipole centers
in CsBr:Eu2+ single crystals and the processes for the formation of such centers during growth of CsBr:Eu single crystals from the melt
by the Bridgman method. We have established that in Cs0.95K0.05Br:Eu2+, more favorable conditions are realized for the formation of aggregate centers than in CsBr:Eu2+ and CsBr0.95K0.05Br:Eu2+ single crystals. So in order to improve the storage properties of phosphors based on CsBr:Eu2+, in particular for increasing the efficiency of PSL excitation, it is expedient to dope them with K+ impurity in a concentration up to 5 mol%.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 627–630, September–October, 2007. 相似文献
11.
Various phenomena: hyperfine shift of 209Bi82+, nuclear decay of 229Th and 169Yb69+ are considered as cross-invariant channels of the internal conversion process from the viewpoint of testing QED. The way
of accelerating nuclear decay in laser field via merging the nuclear and laser photons is discussed. Discovering this fundamental
process would give a convincing test of both QED along with our experimental abilities. 相似文献
12.
通过在稳定连续波运转的Yb:YAG 激光器中插入不同掺杂浓度的新型钠、镱共掺的氟化钙晶体的对比性实验,证明了镱、钠共掺的氟化钙晶体在1050nm具有明显的可饱和吸收作用,从而解释了该晶体作为增益介质在该波段总是趋于自调Q运转的原因.Yb3+离子是该晶体可饱和吸收作用的主要因素,但是共掺入适当的Na离子可以明显改善晶体的调Q效果.优化共掺镱、钠离子的浓度和比例后的氟化钙晶体能够作为1050nm波段激光器的被动Q开关.
关键词:
镱、钠共掺氟化钙
可饱和吸收体
调Q 相似文献
13.
Ag-impurity effects on the first- and second-order quadrupole interaction (QI) at 23Na site in an isomorphic mixed system, Na1−xAgxNO2 (x=0, 0.0084, 0.026, 0.079, 0.094, 0.16), have been investigated by employing 23Na (I=3/2) magic angle spinning nuclear magnetic resonance (MAS NMR) technique. The central transition (CT) and satellite transition (ST) are simultaneously observed with this system. From the spectral analysis, the quadrupole parameter and its distribution width are obtained as a function of Ag concentration. From the intensity loss of CT MAS centerband and of the envelope function of ST MAS sidebands due to impurities, the range of their influence on the second- and first-order QI is estimated. The estimated ranges contain the second and first neighbouring Na sites from the resonating 23Na nucleus for the first- and second-order QI, respectively. 相似文献
14.
采用完全对角化方法,以尖晶石结构的ZnAl2O4:Cr3+,ZnGa2O4:Cr3+和MgAl2O4:Cr3+系列晶体为例,联系晶格局域结构,对三角对称下3d3离子2E态g因子性质进行了研究.研究中考虑了包括自旋与自旋相互作用、自旋与另一轨
关键词:
2E态g因子')" href="#">2E态g因子
3离子')" href="#">3d3离子
尖晶石结构
磁相互作用 相似文献
15.
OH−- and Cu+-codoped NaCl crystals are colored electrolytically by using a pointed anode and a flat cathode at various temperatures and under various voltages. Absorption and fluorescence spectral properties of colored crystals are investigated. Absorption, excitation and fluorescence spectra reveal existence of V2, V2m, V3, OH−, U, UA, O2−–Va+, O2+, Cu+, Cu0, Cu− and OH−-perturbed Cu+ color centers in colored crystals. Formations of color centers are explained. 相似文献
16.
Fluorescence spectra of LiYF4:Pr3+ have been measured between 12,000 and 22,000 cm−1 under pressures up to 10 GPa. In total, 25 crystal field energy levels were obtained and used for the determination of free-ion and crystal field parameters under pressure. According to the nephelauxetic effect, the free-ion parameters decrease with increasing pressure. The relative decrease is larger for the Slater than for the spin-orbit coupling parameter. This behavior is consistent with former studies on Pr3+ in different crystals and can be explained by a special covalency model. According to an effective D2d symmetry, five crystal field parameters B02(f,f), B04(f,f), B44(f,f), B06(f,f), and B46(f,f) are non-zero. The pressure-induced changes of these parameters have been determined up to the maximum pressure of 10 GPa. In order to improve the calculation of the crystal field levels, the configuration interactions with the 4f16p1 configuration have been taken into account. The effect of these interactions are also analyzed under pressure and distinct improvements of the energy level calculations have been obtained. 相似文献
17.
Silvia Olt Eva Krtz Ewald Komor Markus Rokitta Axel Haase 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,144(2):297
23Na NMR microimaging is described to map, for the first time, the sodium distribution in living plants. As an example, the response of 6-day-old seedlings of Ricinus communis to exposure to sodium chloride concentrations from 5 to 300 mM was observed in vivo using 23Na as well as 1H NMR microimaging. Experiments were performed at 11.75 T with a double resonant 23Na–1H probehead. The probehead was homebuilt and equipped with a climate chamber. T1 and T2 of 23Na were measured in the cross section of the hypocotyl. Within 85 min 23Na images with an in-plane resolution of 156 × 156 μm were acquired. With this spatial information, the different types of tissue in the hypocotyl can be discerned. The measurement time appears to be short compared to the time scale of sodium uptake and accumulation in the plant so that the kinetics of salt stress can be followed. In conclusion, 23Na NMR microimaging promises great potential for physiological studies of the consequences of salt stress on the macroscopic level and thus may become a unique tool for characterizing plants with respect to salt tolerance and salt sensitivity. 相似文献
18.
Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO
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The local structure distortion, the spin Hamiltonian (SH)
parameters, and the electric fine structure of the ground state for
Mn2+(3d5) ion in ZnO crystals are systematically
investigated, where spin--spin (SS), spin--other--orbit (SOO) and
orbit--orbit (OO) magnetic interactions, besides the well-known
spin--orbit (SO) coupling, are taken into account for the first
time, by using the complete diagonalization method. The theoretical
results of the second-order zero-field splitting (ZFS) parameter
D, the fourth-order ZFS parameter (a-F), the Zeeman
g-factors: g// and g⊥, and the energy differences of
the ground state: \delta1 and \delta2 for Mn2+ in
Mn2+: ZnO are in good agreement with experimental measurements
when the three O2- ions below the Mn2+ ion rotate by
1.085o away from the [111]-axis. Hence, the local structure
distortion effect plays an important role in explaining the
spectroscopic properties of Mn2+ ions in Mn2+: ZnO
crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals
that although the SO mechanism is the most important one, the
contributions to the SH parameters, made by other four mechanisms,
i.e. SS, SOO, OO, and SO~SS~SOO~OO mechanisms, are
significant and should not be omitted, especially for calculating
ZFS parameter D. 相似文献
19.
P. Deepa R. Vijay Solomon S. Angeline Vedha P. Venuvanalingam 《Molecular physics》2014,112(24):3195-3205
R22(8), a commonly occurring motif in organic crystals, has been examined here through ab initio and density functional theory (DFT) methods. The 11 R22(8) motifs reported by Allen et al. have been classified into five types; their structural features, hydrogen-bonding patterns and the kind of interactions stabilising these motifs have been studied. Results reveal that the electronegativity of donor atoms plays a major role in directing the hydrogen bonds, whereas their positions in the motif have been found to be less important. Quantum theory of atoms in molecules (QTAIM) and reduced density gradient-based non-covalent-interaction analyses have been used to understand the weak interactions between monomers. Homonuclear interactions within the motifs have been found to be stronger with higher covalent character at the bond critical points than heteronuclear interactions. In addition, a localised molecular orbital energy decomposition analysis (LMOEDA) has been accomplished to provide useful insight into various long- and short-range interactions that contribute to the total stabilisation energies. The stabilising n → σ* interactions have been explained using natural bond orbital (NBO) analysis. Overall, this study provides the essential criteria for an organic crystal to be in an R22(8) motif and further discusses the different combinations of hydrogen-bonding features within the R22(8) motifs. 相似文献
20.
The relative nuclear resonance fluorescence (NRF) yield of 1.37 MeV quantas, emitted from Mg24-recoils, was determined in a scattering experiment. In single crystals of Na and NaCl, which were doped with Mg24, a dependence of the NRF yield on the direction of the emitted gamma quantas relative to the orientation of the crystals, was observed. The effect can be explained by taking into account the anisotropic deceleration of the Mg24-recoils in the single crystals. The deceleration was calculated by using Born-Mayer potentials. Results of the calculations of the anisotropic NRF yields are presented and discussed. 相似文献