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.     

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.     

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.     

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.     

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.     

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 selenium

The nuclear quadrupole interaction of Ta-181 in selenium was measured using perturbed angular correlation technique. The electric field gradient at room temperature is 4.56(32) × 10¹⁷ V/cm². The temperature dependence of EFG follows the usual T^3/2 behaviour.     

Electric quadrupole moments and strong interaction effects in pionic atoms of 165Ho, 175Lu, 176Lu, 179Hf and 181Ta

The effective quadrupole moments Q_eff of the nuclei of ¹⁶⁵Ho, ¹⁷⁵Lu, ¹⁷⁶Lu, ¹⁷⁹Hf and ¹⁸¹Ta were accurately measured by detecting the pionic atom 5g-4f X-rays of the elements. The spectroscopic quadropole moments, Q_spec, were obtained by correcting Q_eff for nuclear finite size effect, distortion of the pion wave function by the pion-nucleus strong interaction, and contribution to the energy level splittings by the strong interaction. The intrinsic quadrupole moments, Q₀, were obtained by projecting Q_spec into the frame of reference fixed on the nucleus. The shift, ε₀, and broadening, Γ₀, of the 4f energy level due to the strong interaction between the pion and the nucleons for all the elements were also measured. Theoretical values of ε₀ and Γ₀ were calculated and compared to the experimental values. The measured values of Q₀ were compared with existing results in muonic and pionic atoms. The measured values of ε₀ and Γ₀ were also compared with existing values.     

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.     

Electric quadrupole interaction in hafnium sulphates

A coincidence system is developed which gives a time resolution of =0,8 ns for the 133–482 keV -ray cascade of¹⁸¹Hf. It is applied to the study of EQI in hafnium sulphate salts. In the case of Hf(SO₄)₂ the interaction strength of _Q = 157.8 ± 0.5 MHz is obtained, together with the assymetry parameter =0.531±0.005 and the field distribution parameter =0.003±0.001. The data are compared with point-charge model calculations.A similar set of EQI data is also derived for another unstable and unidentified hafnium sulphate structure.     

The nuclear quadrupole interaction at 111Cd and 181Ta sites in anatase and rutile TiO2: A TDPAC study

The nuclear quadrupole interaction of the I=5/2 state of the nuclear probes ¹¹¹Cd and ¹⁸¹Ta in the anatase and rutile polymorphs of bulk TiO₂ was studied using the time differential perturbed angular correlation (TDPAC) method. The fast–slow coincidence setup is based on CAMAC electronics. For anatase, the asymmetry parameter of the electric field gradient was η=0.22(1) and a quadrupole interaction frequency of ω_Q=44.01(3) Mrad/s was obtained for ¹⁸¹Ta. For rutile, the respective values are η=0.56(1) and ω_Q=130.07(9) Mrad/s. The values for rutile match closely with the literature values. In case of the ¹¹¹Cd probe produced from the beta decay of ¹¹¹Ag, the quadrupole interaction frequency for anatase was negligibly small as indicated by an unperturbed angular correlation in anatase. On the other hand for rutile the quadrupole frequency is ω_Q=61.74(2) Mrad/s and the asymmetry parameter η=0.23(1) for the ¹¹¹Cd probe. The results are interpreted in terms of the surrounding atom positions in the lattice and the charge state of the probe nucleus.     

The study of quadrupole hyperfine interactions in pionic atoms of181Ta and165Ho

Conclusion In Table 3 we have listed the Q values of¹⁶⁵Ho and¹⁸¹Ta obtained by the pionic methods from this experiment and the one from Ebersoldet. al. and also the results by the muonic methods.^{4, 5} They are all in good agreements within the experimental uncertainties around 1%. The large discrepency between the Q values of¹⁸¹Ta from Ref. 5 and Ref. 7 was discussed and explained in detail in Ref. 5.The _o obtained in¹⁶⁵Ho is comparable to the _o calculated by using the Kisslinger's potential. However, the experimental _o for¹⁸¹Ta from this experiment is 28% larger than the theoretical value by Scheck³ by using the perturbation method.As it was mentioned at the beginning of this paper that the strong interaction quadrupole effect introduces characteristic level broadening to each components of the multiplet. The excellent fit between the calculated composite curve with the observed experimental h.f.s. spectra could be obtained only by varying all three independent parameters Q_eff, _o and _o. Without _o, or ₂, no satisfactory fitting could be obtained. That this illustrates the intrigue strong quadrupole effects on each components of a multiplet do behave as predicted by Scheck.³     

Nuclear quadrupole interaction at 181Ta in hafnium dioxide fiber: Time differential perturbed angular correlation measurements and ab initio calculations

The thermal behavior of hafnium dioxide fiber has been investigated with the aid of time differential perturbed angular correlation (TDPAC) technique along with XRD and SEM measurements. This study has proved a good thermal stability of the fibrous material up to 1173 K and the fiber loses its crystallinity to a meager extent at 1673 K. No phase transition has been observed up to 1673 K in this fiber. TDPAC parameters for the HfO₂ fiber annealed at 1173 K are ω_Q=124.6 (3) Mrad/s and η=0.36 (1). These values remain unaltered for the HfO₂ fiber annealed even at 1673 K. Electronic structure calculations based on the density functional theory (DFT) for HfO₂ doped with tantalum impurity have been performed and the calculated EFG parameters are in reasonable agreement with the experimental values.     

Electric quadrupole interaction of recoil-implanted zinc in cadmium

The electric quadrupole interaction of the 605 keV 9/2⁺ state of ⁶⁷Zn in Cd metal was measured by the recoil implantation technique combined with the DPAD method (DIMPAD). The result, ν_Q = eQV_ZZ/h = 39.0(4) MHz (T = 373 K), is compared with the known quadrupole coupling constants in the Zn-Cd system.     

Electric quadrupole interaction of Ce isomers in tin

The quadrupole coupling constants for 10⁺ Ce isomers have been measured in a polycrystalline Sn host. The quadrupole moment ratios are Q[¹³⁸Ce(10⁺)]: Q[¹³⁶Ce(10⁺)]: Q[¹³⁴Ce(10⁺)]=11.45(14)1.71(16). The temperature dependence of the EFG was measured in the range 160–468 K.Incumbent of the Arye Dissentshik Career Development Chair.We thank Dr. A. Abbas for submitting to us the seniority scheme wave functions prior to publication.     

Electric and magnetic interaction in181TaTb measured with TDPAC

The temperature and pressure dependence of the combined magnetic and electric interaction of¹⁸¹Ta in Tb have been measured using the TDPAC method. At 20K the field is 27.6 T and the EFG 7.32 10¹⁷ V/cm². The antiferromagnetic phase is suppressed by the 0.5 wt% Hf and T_C is shifted to 236K. No pressure dependence is observed at 140K in contrast to that of the magnetization while at 208K we obtain dlnB/dP=–13 (2) Mbars–1 essentially due to the pressure dependence of T_C.