TDPAC Technique Research Articles

Measurement of the Magnetic Moment of the First Excited State in 93Sr Using on-line TDPAC technique

The g-factor of the first excited state of 93Sr (E = 213 keV, T 1/2 = 4.6 ns) was measured by an on-line TDPAC technique with use of the strong hyperfine field in Fe metal. The Larmor frequency ω L = (2.60 ± 0.15) × 108 rad/s was obtained. The g-factor is derived as g = −0.227 ± 0.013 from g = −ħωL/B hf µ N. If the spin of the first excited state of 93Sr is assumed to be 3/2, the g-factor is predicted by a simple core-excitation model as g = −0.22, which is in good agreement with the present experimental result.

Study of the local magnetic environment in LaMnO3 perovskite by measuring hyperfine interactions

Abstract TDPAC technique has been used to investigate the hyperfine interactions in the LaMnO3 perovskite using 140La(140Ce) as probe nuclei. Temperature dependence of the magnetic hyperfine field (MHF) at La sites shows an antiferromagnetic behavior with Neel temperature around 142 K. For temperatures below 80 K, however, the values of MHF decrease and deviate from the expected regular behavior.

Influence of electron capture after-effects on the stability of 111In( 111Cd)-complexes with organic ligands

The TDPAC technique was applied to verify a hypothesis about the influence of electron capture after-effects on the integrity of radiometal complexes with organic ligands in aqueous solutions. The neutral aqueous solutions of DTPA-complexes with two parent isotopes, 111In(EC) 111Cd and 111mCd, were used for direct comparison of dynamic interaction parameters. Data for the parent 111In–DTPA complexes revealed three fractions with essentially different relaxation constants, including an “unperturbed” fraction, which, according to the hypothesis, is due to small fragments of the initial complexes disintegrated as a result of Auger-process and the following Coulomb fragmentation. Only one fraction with a relaxation constant of 3(1)×10 6 s −1 was observed for the 111mCd–DTPA solution confirming the proposal about the influence of electron capture after-effects. Measurements with the frozen solutions allowed determining the electric field gradient (EFG) at Cd-sites in complexes with DTPA, V zz=6.7(2)×10 21 V/m 2 with an asymmetry parameter η=0.75(5).

Hyperfine Interactions in Tb 3 In 5

The static quadrupole interaction at the In site of the rare earth intermetallic compound Tb3In5 has been studied at room temperature by TDPAC technique. The results were compared with some Point Charge Model calculations, using 2 or 3 for the In charge, suggesting the value 3. Some additional AC susceptibility measurements indicated that this sample may be antiferromagnetic.

Stability of in 111In-ligand Complexes Studied by TDPAC

Abstract The TDPAC technique has been applied to study the stability of 111In complexes with NTA and DTPA in solutions with different concentrations of stable In at pH = 7. A sample of In-DTPA complexes attached to microspheres of albumin (MSA) has been measured at temperatures of 293 and 130 K. The results show that the products formed after 111ln → 111Cd decay and following Auger-effect are determined by the stability of In (Cd)-complexes with organic ligands. The daughter Cd behaviour depends on the In: ligand mole ratio, from 1: ∞ to 1:1. The possibility of Cd-ligand complex destruction and following Cd rechelating is discussed. The results indicate that the rechelating probability correlates with the stability of the parent and daughter complexes.

Time differential perturbed angular correlation of [formula omitted]-EDTA linked to the single free cysteine of bovine serum albumin

By means of a facile chemical modification of the bovine serum albumin molecule, it was possible to measure its hydrodynamic radius with high accuracy (∼3%) using the TDPAC technique. The new approach presented here allows a wide use of the TDPAC technique to perform high precision studies of backbone dynamics of almost any protein.

Identification of the nitrogenase FeMo cofactor in nitrogen-fixing bacteria using the TDPAC technique

Identification of the nitrogenase FeMo cofactor in nitrogen-fixing bacteria using the TDPAC technique

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.

Intermetallic compound formation at the In-Pd interface investigated with111In local probes

The TDPAC technique was applied to study the formation of In-Pd compounds in bilayer electrodeposited sample doped with the radioactive111In. Subsequent isochronal annealings at increasing temperatures caused the Pd diffusion into the In layer reflected in the quadrupole interactionR(t) curves. The appearing new unique frequencies indicate the formation of ordered In3Pd, In3Pd2 andInPd2 phases in the sample. The identification of this In-Pd compounds was based on the PAC measurements for bulk In-Pd samples with defined stoichiometry.

TDPAC studies on the recovery of Ag plastically deformed at room temperature

The recovery of polycrystalline silver rolled at room temperature to different degrees of deformation (33, 48, 73 and 95%) was investigated by means of the TDPAC technique with a 111Cd probe. The dependence of quadrupole interaction parameters, extracted from time spectra, on the degree of deformation and annealing temperature was studied. At temperatures in the range 350-425 K the recovery stage occurs which is indicated by the decrease of quadrupole interaction. For lower degrees of deformation also a small fraction ( approximately 2%) of sharp quadrupole frequency of 38(1) MHz was detected after annealing at temperatures 300-375 K, associated with vacancy complexes trapped on probe atoms.

Crystallization of amorphous Hf100−xCux alloys

The crystallization of Hf100−xCux (x=33,44,50,59) amorphous alloys was studied by the TDPAC technique. The different stages in the transformation towards equilibrium were investigated through the evolution of the quadrupole perturbation after thermal annealings. The crystallization kinetics of Hf67Cu33 and Hf56Cu44 was analyzed using the Johnson-Mehl-Avrami equation. General trends in the crystallization behavior are discussed.

Study of magnetic behaviour of CeRh3B2 using111Cd probe

Using111Cd probe nuclei, the transferredHhf(T) is measured down to 35 K in CeRh3B2 using TDPAC technique. The angle β between the EFG and the direction of magnetization is obtained to be 90°. The observed smallHhf(T) may be a consequence of the reduced moment on Ce in CeRh3B2.

Structural phase transitions in Pd0.8 Si0.2 and Pd0.75 Si0.20 Ag0.05 alloys observed by pac

The phase transition in the alloys Pd0.8 Si0.2 and Pd0.75 Si0.20 Ag0.05 have been investigated through the quadrupole interaction of111Cd impurities. The quadrupole interactions were measured by means of the TDPAC technique from room temperature up to about 870 K. The variation of the quadrupole interaction with temperature in the alloy PdSiAg shows aT 3/2 dependence below and above 629 K, with coefficientsB=5.43(25)·10−5 K−3/2 andB=3.70(15)·10−5 K−3/2, respectively. This demonstrates that the alloy undergoes a phase transition around 629 K. The existence of two electric field gradients observed in the alloy PdSi,V zz (1)=3.47(54)·1017 V/cm2 andV zz (2)=2.29(36)·1017 V/cm2, indicates that there are two different111Cd sites. The corresponding fractionsf 1 andf 2 strongly depend on temperature. Below 520 K, most111Cd nuclei are subject to the higher EFGV zz (1) (f 1≈70%), whereas above 520 Kf 1 falls rapidly to zero andV zz (2) becomes dominant. The temperature dependences of thef 1 andf 2 reveal a picture of the phase transition between the two crystal structures.

The electric field gradient and its temperature dependence at111Cd in α-Uranium

The magnitude and temperature dependence of the quadrupole interaction at the111Cd site in orthorhombic α-Uranium was investigated between 293 and 17 K. The parent activity111In was implanted into Uranium metal with an energy of 80 keV and the γ-γ TDPAC technique, applied to the 245 keV state in111Cd, was used to measure the quadrupole interaction frequency. The derived electric field gradient for Cd in Uranium was found to be highly asymmetric (η=1) and led to a quadrupole interaction frequency of νQ=7.10(7) MHz at 293 K. The temperature dependence of the quadrupole interaction is very strong, νQ increases to 14.3(2) MHz at 17 K and shows a linear dependence on the temperature.

Magnetic hyperfine fields in Heusler alloys Co YZ (Y=Ti,Zr; Z=Al,Ga,Sn)

Magnetic hyperfine fields (mhf) acting on Ta at the Ti and Zr sites have been measured in Heusler alloys Co2TiAl(Ga,Sn) and Co2ZrAl(Sn) by the TDPAC technique utilizing the 133–482 keV gamma cascade in181Hf. Curie temperatures of all the alloys have also been measured using a vibrating sample magnetometer. Present data together with the existing results on the Co2HfAl(Ga,Sn) are discussed and compared with the mhf systematics in Heusler alloys.

Measurement of local moment on Ce in CeRh3B2

We have employed the TDPAC technique to measure the paramagnetic enhancement factorβ of140Ce in CeRh3B2 in the temperature range 300 K down to 115 K. Our measurements show that above Tc=115 K, the trend forβ(T) closely follows that for trivalent cerium.

Local magnetic susceptibility at 140Ce in RNi5 compounds: R = rare earth

Using TDPAC technique with 140Ce probe nuclei we measured the paramagnetic enhancement factor β in RNi5 compounds (R = La, Ce, Pr). The result that β is close to 1 indicates that cerium is nonmagnetic in these compounds, as in the case of α-cerium.

Temperature behaviour of the electric field gradients in the switching InSe compound

By using the TDPAC technique the authors were able to detect the structural changes suffered by the InSe compound when submitted to a switching process. this was done by measuring the thermal dependence of the nuclear quadrupole frequencies in both electric states of the sample. In the off state, one of the frequencies remains constant through the whole temperature range. The other, instead, follows a linear dependence up to 80K and then the well known T3/2 relationship. In the on state only one frequency appears, which has a linear dependence with temperature.

Time-differential perturbed angular correlations investigation of the (NH4)2ZrF6 thermal decomposition

Via the TDPAC technique and complementary x-ray diffraction analysis, the thermal decomposition of (NH4)2ZrF6 has been observed to occur in the range 400–800 K according to the thermolysis scheme (NH4)2ZrF6→485 KNH4ZrF5→560 KNH4Zr2F9 →620 KZrF4→760 KZrO2. Assuming that the first transformation takes place through the simple chemical reaction (NH4)2ZrF6→NH4ZrF5+NH4F, the corresponding activation energy has been determined to be Ea=(82±6) kJ/mol. The hyperfine parameters of the NH4Zr2F9 decomposition product have been determined between 14 and 560 K. A complete analogy with the isomorphous compound NH4Hf2F9 was observed.

Anomalous temperature behaviour of the electric field gradients in an InSe semiconductor compound

The temperature dependence of the nuclear quadrupole frequencies acting at two sites of indium in an InSe semiconductor compound was measured between 4 and 823 K, using the TDPAC technique. One of the frequencies remains constant through the whole temperature range. The other, instead, follows a linear dependence up to 80 K and then the well-known T 3 2 relationship.