Nuclear electric quadrupole interaction of 182Re (64h) and 183Re recoil-implanted into graphite

Abstract

The technique of static low-temperature nuclear orientation has been used to investigate the nuclear electric quadrupole interaction of implanted ¹⁸²Re (64h) and ¹⁸³Re in thin foils of highly oriented pyrolytic graphite (HOPG) at temperatures down to 5 mK. The isotopes were recoil-implanted at a temperature of 700°C in order to limit the amount of lattice damage. The fraction of nuclei experiencing a large electric field gradient was considerably improved after two successive annealing sessions at 1200°C, from 1.0(0.6)% before annealing to 4.5(0.8)% after 6h and to 11.3(2.0)% after 162 h annealing. The electric field gradient for Re in HOPG is deduced to be V_zz = +5.4(2.6)·10²²V/m².     

Static electric quadrupole interaction of Ce and Pb ions in lead titanate

The static electric quadrupole interaction of¹⁴⁰Ce and²⁰⁴Pb has been studied in polycrystalline PbTiO₃ at the lead site with the time-differential perturbed angular correlation (TDPAC) method. The interaction frequencies areω _Q(2083 keV;¹⁴⁰Ce)=2.11 (17) MHz andω _Q(1274keV;²⁰⁴Pb)=3.60(3) MHz. The results are compared with the electric field gradient calculated in a point charge model. Under the assumption that the covalent contributions for Ce and Pb are equal, one can derive the quadrupole moment of the 1274 keV state of²⁰⁴Pb to be ¦Q¦=0.68 b.     

Nuclear orientation and quadrupole interaction

In quadrupole-interaction nuclear-orientation experiments (QI-NO) the quadrupole interaction frequency V_Q=e²qQ/h is determined from the angular distribution of -rays emitted in the decay of radioactive nuclei oriented at low temperatures as impurities in noncubic single-crystal matrices. This means that either the spectroscopic quadrupole moment Q of radioactive isotopes or the crystal electric field gradient eq can be determined from QI-NO experiments. Recent developments in QI-NO are discussed, especially with regard to the investigation of nuclei far from stability, with the following main topics: (1) Experimental aspects; (2) Quadrupole moments of short-lived nuclei; (3) Systematics of electric field gradients; (4) QI-NO with new host lattices, such as dichalcogenides; (5) Resonance techniques.     

Nuclear quadrupole interaction of199mHg-ferrocenethiol complexes

We determined the^199mHg nuclear quadrupole interaction (NQI) by time differential perturbed angular correlation in the following ferrocenethiol complexes with mercury: ferrocenethiol (v _Q =1253(4) MHz, =0); 1,1-ferrocenedithiol (47%v _Q =1555(8) MHz, =0.13(2); 25%v _Q =726(19) MHz, =0.81(2); rest unspecific); 2-ferrocenyl-ethanethiol (v _Q =1306(6) MHz, =0.17(1)); and a 1, 1-bis (2-mercapto-propylthio)ferrocene oligomer (v _Q =1411(5), =0). All NQIs are rather large with small asymmetry parameters, indicating essentially linear S-Hg-S bonds. The only exception is the minority fraction in 1,2-ferrocenedithiol which suggests the formation of a 1,3-dithia-2-mercura[3]ferrocenophane.     

Nuclear electric quadrupole interactions in liquids entrapped in cavities

Liquids entrapped in cavities and containing quadrupole nuclei are considered. The interaction of the quadrupole moment of a nucleus with the electric field gradient is studied. In such a system, molecules are in both rotational and translational Brownian motions which are described by the diffusion equation. Solving this equation, we show that the intra- and intermolecular nuclear quadrupole interactions are averaged to zero in cavities with the size larger than several angstroms.     

Nuclear quadrupole interaction in the low dimensional hf-trichalcogenides

We report on Time Differential Perturbed Angular Correlation measurements of the nuclear quadrupole interaction of¹⁸¹Hf(β⁻)¹⁸¹ and its temperature dependence in the low dimensional Hf- trichalcogenides HfS₃, HfSe₃ and HfTe₃. In HfS₃ the temperature dependence of the precession frequency is a slowly decreasing function with a negative curvature, the deviation from axial symmetry of the electric field gradient is practically temperature independent. In HfSe₃ the NQI shows a peculiar behaviour; between 10K and 300K the quadrupole frequency and the asymmetry parameter increase, between 300K and 400K the frequency decreases while the deviation from axial symmetry increases, indicating a structural phase transition near room temperature. In HfTe₃ the quadrupole frequency is practically temperature independent below 600K and increases linearely at higher temperatures, the asymmetry parameter increases steadily in the temperature range from 10K to 600K and then decreases. There is a strong correlation between the strength and the asymmetry of the electric field gradient so that the system depends on one control parameter only.     

Nuclear quadrupole interaction at99Tc in molybdenum compounds

The nuclear quadrupole interaction (NQI) at⁹⁹Tc on molybdenum sites in a series of molybdenum compounds was investigated by time differential perturbed angular correlation. The NQI is rather small for compounds with isolated oxygen/sulfur tetrahedra and fairly large for all compounds with condensed coordination polyhedra.On leave from Tanta University, Egypt     

Precision measurement of the electric quadrupole interaction in zinc metal

To decide on the validity of various values for the quadrupole coupling constant of Zn metal available in the literature, we have used the frequency modulation technique to the 93.3 keV Mössbauer resonance of⁶⁷Zn. We obtained for a⁶⁷Zn metal absorber: e²qQ/h =v _O = 12.34 ± 0.03 MHz. The asymmetry parameter was found to be =0.00 _–0 ^+0.06 . These precise values can be used as a calibration standard for⁶⁷Zn Doppler drives.This work has been supported by the Bundesministerium für Forschung und Technologie and by the Kernforschungszentrum Karlsruhe.     

Nuclear alignment of implanted160Tb in highly oriented pyrolytic graphite layers

Low-temperature nuclear alignment of¹⁶⁰Tb ions implanted in Highly Oriented Pyrolytic Graphite has been observed by the anisotropic intensity distribution of γ-rays. The data can be understood with an effective spin Hamiltonian containing combined magnetic and electric hyperfine interactions. Values deduced for the hyperfine parameters are A/k=(101±7) mK for the magnetic interaction, and P/k=(−3.7±0.9) mK for the nuclear electric quadrupole interaction, under the assumption that B=0 and Δ=0. Measurements in magnetic fields of 0.2 and 1.0 T directed along the graphite c-axis showed thermal saturation due to the strongly reduced heat conductivity of HOPG in the presence of a magnetic field.     

Nuclear electric quadrupole moment of41Ca by laser-RF spectroscopy

Zeitschrift für Physik A Hadrons and nuclei - The nuclear electric quadrupole moment of41Ca, which contains a single neutron outside closed proton and neutron shells (N=Z=20) has been...     

Nuclear quadrupole interaction at99Tc in lithium-intercalated molybdenum disulphide

A highly crystalline form of lithium intercalated MoS₂ was investigated by performing TDPAC measurements on the 740 — (44) 141 keV γ?γ cascade in⁹⁹Tc. Analysis of the data reveals the presence of two static efg interactions with the following parameters: $$\begin{array}{*{20}c} {\begin{array}{*{20}c} {v_q = 114(3) MHz,} & {\eta _1 = 0.57(5),} & {\delta _1 = 0.48(5);} \\\end{array}} \\ {\begin{array}{*{20}c} {v_{q2} = 645(19) MHz,} & {\eta = 0.45(5),} & {\delta _2 = 0.11(2).} \\\end{array}} \\\end{array}$$      

Nuclear quadrupole interaction studies of high pressure phase transitions in InSb

Conclusions This study of the behavior of the EFG in the pressure-induced phase transition in InSb shows a high frequency in the high presure metallic phase, that is compatible with the tetragonal, -Sn like structure, but with a certain degree of imperfection. If this imperfection is in fact some disorder in the In and Sb positions, its amount could be promptly clarified by neutron diffraction, since the similarities of the atomic numbers of In and Sb preclude any easy measurement of superlattice lines by X-ray diffraction techniques.The strong frequency distribution that remains after the reversal of the phase transformation must be related with the peculiar kinetics of this reaction, since it depends on temperature and the time interval and since the same is not observed in the T1 transition. So it seems interesting to study other phase transitions in similar systems. A clarification of the precise nature of the generated defects demands the application of other techniques like transmission electron microsconv and neutron diffraction.If the defects observed here are in fact boundary of domains, it might be possible to relate the domain size with the frequency distribution and then to study, by TDPAC, the kinetics of formation and growth of these domains.Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq) and Financiadora de Estudos e Projetos (FINEP)     

Nuclear spin echo in magnetics with inhomogeneous hyperfine and quadrupole interaction

Additional spin-ocho signale from quadrupole nuclei with I=7/2 (Co⁵⁹ nuclei in Co and Fe−Co thin films) were investigated. It has been shown, that the time dependence of the additional ocho signals, arising at the time moments 2nς reflect quadrupole interaction inhomogenety.     

Nuclear quadrupole interaction in metals: Experiments, calculations, models

The results obtained from the investigation of the nuclear quadrupole interaction in metals, mostly at impurities, are reviewed. Examples of the experimental work are primarily taken from studies at ISOLDE/CERN. For the determination of the nuclear quadrupole moments Q, necessary to extract the electric field gradients from the measured coupling constants, various methods have been employed. Band structure calculations both for pure systems and also for impurities have been performed with the FLAPW density functional method. The theoretical understanding achieved for sp-impurities in simple noncubic metals is described. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evidence of the electric quadrupole coupling of 57Fe implanted in silicon

The conversion electron Mössbauer spectra of ⁵⁷Fe implants in silicon were measured in an applied strong magnetic field. The existence of axial, positive quadrupole coupling at iron nuclei was established.     

Structural phase transition in cadmium titanate observed by electric quadrupole interaction

The quadrupole interaction at¹¹¹Cd nuclei was measured in the ferroelectric perovskite CdTiO₃ at different temperatures using the PAC method. The interaction parameters indicate a structural phase transition around 50 K.     

NMR-ON measurement of the electric quadrupole interaction of199Au in Fe

The magnetic-dipole and electric-quadrupole interaction frequencies of¹⁹⁹AuJ ^π=3/2⁺ T _1/2=3.1 d) in Fe were measured with nuclear magnetic resonance on oriented nuclei as 166.69(4) MHz and ?1.52(2) MHz, respectively. This quadrupole splitting is in disagreement to the value previously reported.     

Temperature dependence of electric quadrupole interaction of181Ta in HfO2

High-resolution TDPAC determination of EQI of¹⁸¹Ta in HfO₂ is performed. Room temperature parameters of ω_Q = 111 (1) MHz and η=0.36(1) are obtained. The temperature dependence of ω_Q and η in the range 78–1100 K is established. An explanation of the observed phenomena in a dielectric lattice is discussed.     

Nuclear orientation study of the quadrupole interaction for Co in PdCo alloy

The angular distribution anisotropy of -radiation was measured following the decays of⁵⁸Co and⁶⁰Co oriented at low temperatures in the ferromagnetic PdCo alloy. The ratio of the electric quadrupole to magnetic dipole interaction constants for the⁶⁰Co was deduced to be P/a_o=0.001±0.003, where P=3e²qQ/4I(2I-1) and a_o=H/I.