Quadrupole interaction at181Ta in tellurium

The quandrupole interaction at¹⁸¹Ta in tellurium measured at various temperatures revealed two unique sites with an axially symmetric electric field gradient. These are interpreted as a near substitutional site with almost octahedral symmetry and a pure interstitial site in the tellurium lattice. The temperature dependence observed for QI frequencies corresponding to these sites supports this conclusion.     

Quadrupole interaction at181Ta in BaHfO3

BaHfO₃ is prepared by sintering a mixture of BaCO₃ and HfO₂ giving the same heat treatments as for YBa₂Cu₃O_7– (YBCO). X-ray diffraction analysis confirms the formation of cubic BaHfO₃ along with some unreacted HfO₂. A¹⁸¹Ta TDPAC study of the sample, prepared using neutron-irradiated HfO₂ and BaCO₃, shows a relaxation process to be present in the sample. The value of the relaxation constant0.26 ns is unusually large and temperature independent.     

The quadrupole interaction at181Ta in Zn

The quadrupole interaction (QI) in hexagonal close packed zinc lattice was measured using the 482 keV, 10.6 ns probe state of¹⁸¹Ta employing the time-differential perturbed angular correlation technique. The electric field gradient (EFG) at¹⁸¹Ta in Zn was derived from the measured quadrupole interaction frequency at room temperature asV _zz =12.202×10¹⁷ V/cm². The quadrupole interaction measured at various temperatures displayed normal temperature dependence similar to that seen by this probe in many non-cubic hosts.     

Electric quadrupole interaction at181Ta in RNi5 compounds

The time differential perturbed angular correlation measurements in PrNi₅, NdNi₅, GdNi₅, DyNi₅ and ErNi₅ rare-earth intermetallics with¹⁸¹Ta as probe nuclei have revealed that these impurity nuclei experience a non-axial electric quadrupole interaction. In all the cases, except in GdNi₅, the interaction frequency has a single value in the range 15–20 MHz with asymmetry parameter 0.98. In GdNi₅, however, there are two interaction frequencies (13.61 MHz and 26.89 MHz), the former being the dominant one (90%) with 0.35 and the latter (10%) with 0.98. It is concluded that in all cases the probe nuclei experiencing the highly asymmetric electric field gradient (efg) occupy the unique Ni(3g) site. Annealing studies have shown that in the case of GdNi₅ the interaction gets highly damped, while there is negligible effect in the other cases. The temperature variation of the efg in all cases seems to follow the empiricalT ^3/2 relation.     

Quadrupole interaction at Ta and lattice location of Hf in Be

The time-differential perturbed angular correlation technique (TDPAC) has been applied to the 482 keV excited state of¹⁸¹Ta, to determine the nuclear electric quadrupole interaction (QI) at Ta in Be. Sources were prepared by ion-implantation of¹⁸¹Hf in Be. Particle channeling measurements have revealed that. Hf impurities implanted in Be reside primarily at the tetrahedral interstitial site. The fundamental QI frequency obtained for Ta at this interstitial site in Be is |v _Q| =e ² qQ/h = 227.0 ± 2.2 MHz which corresponds to an electric field gradient |eq|=(3.71±0.15)×10¹⁷ V/cm². This result is discussed in terms of results for Cd impurities in the same system and the systematics of the impurity QI in metals.     

Hyperfine interaction of 181Ta in nickel

Nuclear gamma resonance spectroscopy was used to study the hyperfine interaction of ¹⁸¹Ta impurities in nickel at room temperature and above the Curie point. Both the hyperfine field for ¹⁸¹Ta in nickel at room temperature and the isomer shift relative to Ta metal have been derived.     

Electric quadrupole interaction at181Ta in tetragonal C16 intermetallic compounds

The TDPAC technique was employed for studies of the hyperfine interaction of¹⁸¹Ta in the Hf₂Ni and Zr₂Ni compounds with Al₂Cu-type structure. A linear temperature dependence of the quadrupole frequencies was measured in the temperature region 300–1100 K.     

Electric quadrupole interaction of181Ta in Pd and Zn

A strong electric field gradient (EFG) has been observed at¹⁸¹ Ta in Pd and Zn metals using DPAC technique. The value of the EFG in Pd is found to be 12.5(8)×10¹⁷ V/cm² with an asymmetry parameter () of 0.33(2). The value of the EFG in Zn has the same value as in the Pd metal, but the asymmetry parameter has the value 0.36(3). The variation of EFG in Pd with temperature has shown a weak dependence. The results are interpreted in terms of oxygen trapping at Hf atoms during the sample preparation.     

Orientation of the oxygen-induced non-axially symmetric electric field gradient at181Ta in Ta

The interaction of dilute¹⁸¹Ta in Ta with interstitial oxygen has been investigated via the γ-γ TDPAC-technique applied to the 482 keV state in¹⁸¹Ta. The trapping of Oxygen leading to a quadrupole interaction frequency ν_Q=580(5) MHz with an asymmetry parameter of η-0.37 (1) has been observed after melting the radioactive parent isotope¹⁸¹Hf with Ta. The temperature dependence of the quadrupole interaction frequency between 17 K and 293 K was found to be very weak whereas η varied by about 10%. In a single crystal experiment the orientation of the three principal axes of the electric field gradient leading to ν_Q was determined. The V_zz-axis points in <110>, the V_yy-axis in <100> and the V_xx-axis in <110> direction. These results can be understood in the charge cloud model, suggested by Wrede et al. /1/ for a similar situation found in the HfNb system.     

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.     

Rotational bands in 181Ta

High-spin states in ¹⁸¹Ta have been studied via the ¹⁷⁶Yb(¹¹B,α2n) reaction at 52 MeV using the PEX array and at 57 MeV using the NORDBALL array, with α-particle detection. The previously known, K^π=(7/2)⁺ ground state band and K^π=(9/2)⁻ band have been extended to spins (29/2)⁺ and (31/2)⁻, respectively. Two new one-quasiparticle bands, the K^π=(5/2)⁺ band built on the known (5/2)⁺ isomer and a K^π=((1/2)⁻) band have been observed. Two other rotational bands with three-quasiparticle structure, K^π=(15/2)⁻ and ((19/2)⁺ with π(7/2)[404]ν²(1/2)[510](9/2)[624] and π(9/2)[514]ν²(1/2)[510](9/2)[624] configurations, respectively, have been newly observed. The half-life of the K^π=((19/2)⁺) bandhead which decays to the head of the (15/2)⁻ band has been measured to be 140(36) ns. However, transitions from the ((19/2)⁺) state to the (15/2)⁻ band have not been observed. Received: 26 August 1998     

Hyperfine Interactions at 181Ta in Hf2Co7

In this paper we report a time differential perturbed angular correlation (TDPAC) study of hyperfine interactions at ¹⁸¹Ta in Hf₂Co₇ compound. The TDPAC measurements have been performed in the temperature range 77–1023K. The measured spectra showed broad distribution of hyperfine interactions up to 388K. Above this temperature, in a reversible manner, two nuclear electric quadrupole interactions (EQI) have been observed: at 393K, _Q1=449.0(27)MHz, ₁=0.00(4) and _Q2=144.7(41)MHz, ₂=0.44(2). Since the Curie temperature for this compound is known from the literature to be around 420K, only magnetic order transition could be responsible for such an observation. However, the measurements of magnetization did not exhibit any drastic change in this temperature range.     

The electric quadrupole interaction of181Ta in the Hf−As system

The temperature dependence of the electric quadrupole interaction of¹⁸¹Ta in the Hf?As system has been investigated using the time-differential perturbed angular correlation technique. The sample was prepared by thermal diffusion of¹⁸¹Hf into arsenic metal and the measurements were made at 77, 300, 423, 573 and 673 K. Two quadrupole interaction frequencies were observed which had considerably high values and showed little variation over the entire temperature range. A TEM analysis of the sample showed the presence of two intermetallic compounds HfAs and HfAs₂ to which the two frequencies were assigned.     

Quadrupole interaction at57Fe in zirconium metal

The nuclear quadrupole interaction at⁵⁷Fe nuclei in hcp -zirconium metal is measured in the temperature range 4.2 to 560 K using Mössbauer spectroscopy of⁵⁷Fe. The quadrupole splitting at room temperature is measured to be 0.660(8) mm/sec which corresponds to an electric field gradient of |eq|=3.17×10¹⁷ V/cm² at the⁵⁷Fe nucleus in a -Zr host. As has been observed in many other systems, the results show significant electronic contributions. The temperature variation of the quadrupole interaction is much stronger than is expected from the lattice contributions and is found to follow theT ^3/2 dependence approximately.⁵⁷FeZr does not follow the universal correlation betweeneq _ion andeq _el observed in most of the normal metal hosts but follows the trends recently observed by Krusch and Forker for the transition metal hosts. Our results are compared with the predictions of the conduction electron charge shift model recently proposed by Bodenstedt and Perscheid.     

Quadrupole interaction at111Cd in rare-earth intermetallics

Quadrupole interactions at¹¹¹Cd in various rare-earth intermetallics have been investigated. The enhancement in the efg due to the electronic configurations is found to be small in contrast to pure metals.The authors thank K. Raghunathan for helpful discussions.     

Hyperfine interaction study of electric field gradient in hafnium phosphide using181Ta probe

The hyperfine interaction of¹⁸¹Ta in HfP has been investigated by time differential perturbed angular correlation method which yielded interaction frequencyv _Q=630.20(15) MHz. The observed electric field gradient is calculated to be 1.66(25) × 10²⁰ V/m².     

Quadrupole interaction at111Cd nuclein in single-crystalline thallium

The quadrupole interaction of¹¹¹Cd nuclei in a single crystal of hexagonal thallium has been investigated for different geometries and sample temperatures employing the perturbed - angular correlation technique. The observed variation of the electric field gradient with temperature is attributed to local modes of thermal vibrations of the Cd impurities. An analytical relationship has been derived from lattice-dynamical models, expressing the temperature dependence in terms of impurity-host mass ratios and local force-constants.     

Quadrupole interaction at169Tm in orthorhombic TmF3

Quadrupole interaction data recorded by Triplett et al for the C_1hTm site in TmF₃ are analysed via semi-empirical procedures, one of which employs rank 2 CF parameters derived from the¹⁵⁵Gd: GdF₃ Mössbauer results of Katila et al. The fitted crystal field interactions are compared with available optical spectroscopy results.