Differential Angular Correlation Research Articles

Measurement of electric quadrupole moment in neutron rich $$^{131,132}$$I

The quadrupole moments of the excited levels in neutron rich iodine isotopes, viz., $$^{131}$$ I (5/2 $$_1^+$$ ) and $$^{132}$$ I (3 $$_1^+$$ ), have been measured with LaBr $$_3$$ (Ce) detectors using Time Differential Perturbed Angular Correlation (TDPAC) spectroscopy. The excited levels were populated from $$\beta ^-$$ decay of the radiochemically separated tellurium (Te) fission products produced in $$^{nat}$$ U( $$^4$$ He,f) reaction at E $$_{\alpha }$$ (lab) = 40 MeV from K-130 cyclotron at VECC, Kolkata. The active tellurium fission products were radiochemically doped in metallic tellurium matrix to provide the necessary Electric Field Gradient (EFG) required for TDPAC measurement. The values of quadrupole moments for the 5/2 $$_1^+$$ level of $$^{131}$$ I and 3 $$_1^+$$ level of $$^{132}$$ I were determined to be $$(-)$$ 0.30(1) eb and (−)0.25(2) eb, respectively. The present measurement provides the first experimental determination on the electric quadrupole moment of 5/2 $$_1^+$$ level of $$^{131}$$ I.

Pion-induced pion production in heavy-baryon chiral perturbation theory

We study the reaction $\ensuremath{\pi}+N\ensuremath{\rightarrow}2\ensuremath{\pi}+N$ within the framework of heavy-baryon chiral perturbation theory of chiral order three. The reaction cross section from threshold up to pion laboratory kinetic energies of 400 MeV is found to be in reasonable agreement with experimental data. A host of differential cross sections and angular correlations are also calculated and are found to be in semiquantitative agreement with the data. We find that contributions from amplitudes of chiral order three are large and play an essential role in reproducing the experimental data. Unitarity corrections arising from the imaginary parts of the loop-level Feynman diagrams are the only parameter-free predictions of the present calculations. It is found that the unitarity effects in some reaction channels are sizable. Finally, we evaluate polarization observables (asymmetries) for the transverse polarization of the proton target and find that the asymmetries are generally small ($\ensuremath{\le}0.4$) for the reaction under consideration.

Study of hafnium complexes by time differential perturbed angular correlation technique

Abstract Complexation of hafnium with two ligands viz. diethylene triamine pentaacetic acid (DTPA) and its dimethyl ester derivative (DMDTPA) has been studied by using time differential perturbed angular correlation (TDPAC) technique. Nuclear quadrupole coupling constant (ν Q), asymmetry of the EFG (η) and the frequency distribution (δ) for these complexes have been obtained. Square antiprism structures have been suggested for these complexes using these parameters. A systematic trend of the ν Q has been observed in these and other hafnium complexes with similar ligands and has been explained in terms of the electronegativity of the donor atoms in the ligands.

Investigation of quasimolecular states in 24Mg* through the analysis of the angular dα correlations in the 12C(14N, d)24Mg(α)20Ne reaction

Theoretical analysis of the differential cross sections and angular correlation functions in the 12C(14N, d)24Mg*(α)20Ne reaction at the energy of the incident nitrogen ions E lab=29–42 MeV is performed in the models of the direct transfer of 12C cluster and the compound nucleus. Amplitudes of the reduced widths for the excited quasimolecular states like 12C ⊗ 12C* in the 24Mg nucleus are obtained. The effect of various states of the relative motion of nuclei in the 12C + 12C* configuration on the angular dα-correlation functions is studied.

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, νQ1=449.0(27)MHz, η1=0.00(4) and νQ2=144.7(41)MHz, η2=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.

Dynamics of the Reaction O(3P) + H2S → OH + SH. 2. State-Resolved Differential Cross Sections and Angular Momentum Correlations

Measurements are reported of Doppler resolved polarized laser-induced fluorescence of the OH product of the O(3P) + H2S reaction, leading to estimates of the differential cross sections and angular momentum correlations in the system. O(3P) was produced with translational energy above the barrier to reaction by the polarized 355 nm photolysis of NO2. Three quantum states were studied in detail. For the most populated OH level, v‘ ‘ = 1, N‘ ‘ = 6, the scattering for the A‘ ‘ Λ doublet was found to be largely sideways/backward, with the remaining energy appearing as product translation, and measurements of average Λ doublet scattering showed similar behavior for the A‘ Λ doublet. The same scattering dynamics were observed for the v‘ ‘ = 0, N‘ ‘ = 13 state. For the rotationless v‘ ‘ = 1, N‘ ‘ = 1 state the results were more ambiguous, but if the same distribution of available energy appeared in the SH fragment as deduced for the measurements on rotationally excited OH, then the scattering was seen to be clea...

Evidence of “penetration effects” for the 94 keVK-allowed unhindered transitionin169Tm

From the time differential angular correlation measurement of the 94-63 keV cascade in {sup 169}Tm, a pure {ital M1} character of the 94 keV {gamma} ray is suggested in contrast to the 4{percent} {ital E2} admixture observed in conversion coefficient measurements. Our result indicates {open_quotes}penetration effects{close_quotes} on the internal conversion processes for the 94 keV transition. The observation of penetration effects for a {ital K}-allowed unhindered transition is probably the first. The magnetic moment of the 379 keV state has been remeasured, and the value [{mu}=(3.04{plus_minus}0.14){mu}{ital {sub N}}] is in close agreement with the theoretical prediction (4.5{ital {mu}{sub N}}). {copyright} {ital 1997} {ital The American Physical Society}

Pressure dependence of the electric field gradient in Sb and Sb1?x M x (M=ln, Zn, Ge, Pb, Cd, Sn) at the site of111Cd

Using the111Cd-TDPAC (time differential perturbated angular correlation) method, the pressure dependence of the electric field gradient (EFG) in Sb and Sb1−xMx (M=ln, Zn, Ge, Pb, Cd, Sn) was investigated. The application of a phenomenological ansatz for the parametrisation of the pressure and temperature dependence of the EFG made it possible to combine temperature data gained in former studies [1], [2] with the pressure dependent data presented in this paper. The resulting pressure dependence of −2±0.2 MHz/kbar is shown to be independent of concentration and element of admixture. Results for the volume and explicit temperature dependence agree with existing information on the mixed system Sb1−xMx (M=ln, Zn, Ge, Pb, Cd, Sn); the investigation of the EFG in Sb1−x−yMxPby showed that the resulting EFG may be interpreted as the weighted sum of the individual contributions of the two metals.

Angular correlation and differential cross sections in e--H(1 (2)S-3 (2)P) excitation.

Differential cross sections and angular correlation parameters are calculated for electron-impact excitation of the 3 $^{2}$P state in hydrogen from the ground ${1}^{2}$S state using a distorted-wave approximation. The calculations are compared with the recently reported experimental and close-coupling theoretical results of J. F. Williams, A. T. Stelbovics, and I. Bray [J. Phys. B 26, 4599 (1993)]. Present results show reasonably good agreement with both of their theoretical and experimental results.

Differential cross sections and angular correlation functions in electron-hydrogen scattering for energies betweenn=3 andn=4 thresholds

Differential cross sections and electron-photon angular correlation functions for electron impact excitation of hydrogen atoms in the energy range between then=3 andn=4 thresholds were calculated using the algebraic variational method. The cross sections and correlation functions show complicated and irregular structures associated with overlapping resonances in different partial waves. The availability of these quantities may help interested experimentalists to determine resonance positions, and also may furnish an important test of the adequacy of the computations.

Differential angular correlation of the 1408–122 keV cascade and the g factor of the 122 keV 2+ level of 152Sm

Time-differential angular-correlation measurements on the 1408–122 keV cascade of 152Sm were performed in liquid EuCl3 and Eu(NO3)3 sources at a time resolution of 450 ps. The results obtained are λ2 = (8.3 ± 2.0) × 107 s−1, A2(0) = 0.218 ± 0.008 in SmCl3 and λ2 = (2.5 ± 2.1) × 107 s−1, A2(0) = 0.206 ± 0.018 in Sm(NO3)3. Integral angular-correlation measurements on the 244–122, 964–122, and 1112–122 keV cascades were also performed in the same chloride and nitrate sources using a NaI(Tl)–HPGe system. Using the values of λ2, the unperturbed angular-correlation coefficients for these cascades are determined and therefrom the mixing ratio of the λ transitions are found to be δ(1408) = 0.05 ± 0.01, [Formula: see text] and [Formula: see text]. The magnetic moment of the 122 keV 2+ level was remeasured and a value of μ = 0.80 ± 0.06 nm was obtained.

Differential Cross Section and Angular Correlation Parameters for Electron Impact Excitation of the 31PState of Magnesium

Distorted wave approximation results for the differential cross section and various angular correlation parameters concerning electron impact excitation of the 3 1 P state of magnesium from the ground 3 1 S state are presented and compared with recent experimental data and other theoretical calculations. The comparison of the present calculations with the experiment suggests the suitability of the distorted wave approximation to describe the 3 1 S -3 1 P transition in magnesium at 40 eV.

Electrointercalation of Cu into 2H-TaS2: in situ monitoring of reaction and Cu mobility

We investigated the181Ta nuclear quadrupole interaction (NQI) in crystals of Cux TaS2 by time differential perturbed angular correlation (TDPAC) both in situ during galvanostatic intercalation at 300 K and subsequently between 11 K and 813 K. During electrointercalation the spectra show broad frequency distributions due to slowly diffusing Cu+ in the van der Waals gap.

Impact of BaF2 detectors on nuclear solid state investigations

High resolution time differential angular correlation, now achievable at low cost by the fast and efficient BaF2 detectors, will be introduced from some examples recently worked out. The results obtained manifest a new impetus for this technique in its extended application to particular problems in nuclear solid state research.

Electric field gradient for indium in Sb and Bi semimetals

Using time differential pertubed angular correlation technique we have measured QI frequency at117In in semimetals Sb and Bi at temperatures 77 K and 300 K. The drastic difference of νQ for117In and119In in these hosts suggests two sites for the probes due to different methods of sample preparation. The magnitudes of EFG deviate completely from those predicted by covalent bond model but they seem to fit in the general trend for111Cd and117In QI frequencies in metallic hosts.

Angular correlation parameters and differential cross sections in electron-lithium scattering

A two-potential approach is used to obtain the differential cross sections (DCS) and angular correlation parameters for the resonance (2s to 2p) excitation on the lithium atom by electron impact at energies of 10, 20 and 60 eV. The DCS are also presented for the forbidden (2s to 3s) transition. The computed results are compared with other theoretical calculations and experimental data.

A comparative study of the second-order Born and Faddeev-Watson approximations for electron-atom collisions

Simplified versions of the second-order Born and Faddeev-Watson approximations are applied to the excitation of the n=2 levels of atomic hydrogen by the impact of 54.4 eV electrons. The theories are compared with the measurement of differential cross sections and angular correlation parameters. The results indicate that the Born approximation is better at low angles of scattering but that the Faddeev-Watson approximation is better at high angles. The importance of the phases of the two-body T matrices in the Faddeev-Watson approximation is illustrated.

Excitation of atomic hydrogen by electron impact in an on-shell Faddeev-Watson approximation

The second-order Faddeev-Watson approximation is applied to the excitation of atomic hydrogen by electron impact. By restricting the total kinetic energy of the electrons in the intermediate state to the three-body energy shell a simplification is effected when approximates the dynamics to a double Coulomb binary encounter. The resulting transition matrix elements involve multi-dimensional integrals which are evaluated numerically. Although the model fails for low momentum transfers it predicts differential cross sections and angular correlation parameters for electron-hydrogen excitation which are in reasonable agreement with experiment at high momentum transfers.

Effect of polarization and absorption on differential cross sections and angular correlation parameters for electron excitation of helium

The effects of local polarization and absorption potentials on differential cross sections and angular correlation parameters are studied within the distorted-wave approximation for electron excitation of the $2^{1}P$ state of helium. For examining the effect of local polarization, we have compared a recent numerical self-consistent adiabatic polarization potential for helium with the commonly used hydrogenic adiabatic polarization potential. Different radial regions for the polarization potential were studied to determine their contribution to the overall effect of polarization. Calculations are also presented which show the effects of different strengths for a local absorption potential.

Gamma-gamma angular correlation study of oxygen motion in yttria-stabilized zirconia

The nuclear quadrupole relaxation of 181Ta in ZrO 29 mole% Y 2O 3 has been measured by time differential angular correlations between 350 and 1150°C. The results are consistent with a distribution of the activation energy controlling the local motion of oxygen vacancies.