Angular Correlation Studies Research Articles

Ion channeling and perturbed angular correlation (pac) studies of In-As atom Pairs in silicon

Ion channeling and PAC measurements were used to show that InAs atom pairs were formed during epitaxial regrowth of In-implanted Si(As). The pairs had an electric field gradient characterized by a frequency ν q = 229 MHz and a 〈111〉 axial symmetry which implied either substitutional or tetrahedral interstitial sites of In atoms. The binding energy of the pairs was strong, as determined by measurement of their thermal equilibrium concentration. Ion channeling data showed that this binding caused an enhanced In solubility in As-doped Si, and that the In atoms in the pairs occupied substitutional lattice sites, rather than tetrahedral interstitial sites. At high As concentration, In-As 2 atom clusters were also observed, and these In atoms were also substitutional.

Angular correlation studies of thin metal films

AbstractAngular correlation of positron annihilation radiation is widely used in solid state physics studies (Goldanskii; Hautojärvi), in the defectoscopy of monocrystals in particular (Nielsen et al.). The interest to surface studies gave rise recently to very sophysticated and expensive method of positron beams (Goldanskii et al.). The recent study and recently published papers (Aravin et al.; Valiev et al.) demonstrate, however, that valuable information on surface properties can be obtained using the traditional angular correlation (AC) technique.

Time differential perturbed angular correlation (TDPAC) study of some hafnium glycolate complexes

Time differential measurements of the 133–482 keV γ—γ angular correlation of 181Ta have been performed in solid hafnium complexes of the type [Hf(glycol) 4] (glycol = p-chloromandelate, p-bromomandelate, b-naphthylglycolate and mandelate). The quadrupolar frequencies (ω Q) were found to increase within the series. This behaviour was explained by supposing a dissipation of electronic density at the metal level, caused by an increase in intermolecular hydrogen bonding in the complexes throughout the series studied. These results seem to agree with complementary data from IR spectroscopic studies.

The suitability of 160Tb as a PAC probe for studies of biomolecules

The γ-ray perturbed angular correlation (PAC) studies were made with 160Tb as a probe in MES (2[N-morpholino]-ethane sulphonic acid) solutions of various concentrations. The measurements indicate no influence of concentration of the environment on its interaction with Tb 3+ ion and as such reveal the fact that 160Tb is not a good probe for PAC studies.

Polarization and angular correlations in electron-ion collisions

Studies of polarization and angular correlations in electron-ion collisions can reveal a wealth of information about the collision dynamics. Three different processes are considered as an application of the electron-atom problem: Electron-ion scatterings; electron-impact ionization of ions; and radiations from residual ions. The polarization and angular correlations are presented in concise parametrized expressions in terms of known functions of angles. Angle-independent dynamic parameters in the expressions provide a convenient classification of dynamic effects and facilitate comparison between theory and experiment.

The[g 9 2/2 ]8+ state in96Zr

An 8+ state has been identified at 4390 keV in the doubly semi-magic nucleus96Zr through the study of angular correlations among the γ radiation which is emitted in the β− decay of the 10 s isomer of96Y. This state probably has the configuration πg 2/29 and is populated through a GT decay from the 8+ member of the [πg9/2⊗νg7/2] multiplet in96Y. The deexcitation indicates that it belongs to a band based on the 0+ state in96Zr.

Study of Elastomer Structure Microdefects by Positron Annihilation

A complex lifetime and angular correlation study of positron annihilation in a wide range of polymers and elastomers is carried out. Pick-off annihilation from the localized states is found to be the main mechanism of positron annihilation in the studied elastomers. Influence of elementary free volumes of polymer structure as well as of chemical composition (presence of polar groups) of polymer chain elements on the concentration of positron traps is considered. Effective sizes of positron traps are found ranging from 6 up to 15 A. It is demonstrated that the nature of positronsensitive centres is determined by the distortions in polymer chains packing close to the rigid, side groups and in places of deviations of shape of polymer chains from the linear one. [Russian Text Ignored].

Mössbauer and time-differential perturbed angular correlation studies of the hydrides and deuterides of vanadium

Hydrides and deuterides of vanadium were studied by source and absorber Mössbauer experiments with the resonances of 99Ru, 193Ir and 197Au and by perturbed angular correlation experiments with the 353 — 90 keV γ-γ cascade in 99Ru. The observed isomer shifts and electric quadrupole interactions are discussed in terms of the local environment of the probes in the different hydride and deuteride phases and compared with similar results for the Nb-H system.

Factorization of helicity amplitudes and angular correlations for electroweak processes.

Reliable information on the gauge coupling between W's and Z's can best be obtained from studying angular correlations of electroweak processes. A simple, general method of directly writing down helicity amplitudes for tree diagrams suitable for studying angular correlations is presented. Emphasis is placed on factorization properties of these amplitudes which automatically exhibit the physical energy and angular dependences in explicit form. Illustrative examples, including ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${W}^{+}$${W}^{\mathrm{\ensuremath{-}}}$, are worked out in detail. Applications to angular-correlation studies are outlined.

Angular correlations in the φφ system and evidence for hadronic ηc production

The paper describes a study of angular correlations in the φφ system produced in the reaction π − Be → φφ + X at 85 GeV/ c. A sample of 33 851 candidate φφ events with φφ mass less than 3.2 GeV/ c 2 was obtained in an experiment using the OMEGA spectrometer at CERN with a 4-kaon trigger. Moments of the decay angular distributions are presented as a function of φφ mass over the range 2.0 to 3.2 GeV/ c 2. The distributions in the mass interval 2.0–2.5 GeV/ c 2 are best fitted by a dominance of J P = 2 +. A signal in the H(222200) moment in the mass interval 2.9–3.0 GeV/ c 2 is interpreted as due to η c → φφ and yields a value for (ross section) × (anching ratio) = 14.1 ± 6.3 nb/nucleon.

ChemInform Abstract: Binding of Indium, Used in the Perturbed γ‐γ Angular Correlation Studies, on DNA and DNA Moieties.

AbstractThe two successive γ rays emitted from bound indium (IIIIn) are utilized in the title (PAC) method for the study of molecular dynamics of cellular macromolecules such as DNA.

Perturbed angular correlation and Rutherford backscattering studies in indium implanted silicon

Si (n-type. 0.11 Ω cm) was implanted either with radioactive 111In or natural 115In atoms. The annealing behaviour and defect trapping at the 111In site was studied during isochronal annealing by means of the perturbed γ-γ angular correlation technique (PAC). Amorphisation and recrystallisation were controlled by RBS as a function of the implantation dose and the annealing temperature and were monitored by RBS.

Blurred images of complete fusion and incomplete fusion: Reaction simulation analysis of fission-fragment angular correlations

We use Monte Carlo reaction simulation calculations to reassess several studies of fissionfragment angular correlations. The reactions chosen are 15–30 MeV/nucleon14N +238U and 14.6 MeV/nucleon20Ne +197Au. Reanalysis by means of these stimulations leads to much lower limits than originally reported for the fraction of complete fusion. We infer that at these energies the probability is very large for the direct emission of at least one light particle prior to fission. This implies that the distinction between “complete fusion” and “incomplete fusion” has become blurred beyond meaningful distinction.

Correlation among target fragments produced in a heavy-ion interactions: search for shock-wave phenomenon

This paper presents a study of two-particle inclusive angular correlations among "black" and "grey" particles produced in the interaction O16 nuclei with photoemulsions at 2.1 GeV/nucleon. The experimental data have been compared with the Monte Carlo simulated values assuming an independent emission. It has been observed that there is some short-range correlation among the target fragments, which may indicate shock-wave formation.

Binding of indium, used in the perturbed γ-γ angular correlation studies, on DNA and DNA moieties

The two successive gamma rays emitted from bound indium ( 111In) are utilized in the Perturbed γ-γ Angular Correlation (PAC) method for the study of the molecular dynamics of cellular macromolecules such as DNA. In this paper, evidence is presented indicating that indium binds on both phosphate and the base moieties of DNA and of the nucleotides and that, the binding of indium, under the conditions used in the PAC method, does not alter the hydrodynamic properties of the DNA macromolecule or its UV absorbance spectrum.

Etude des interactions In 3+ligande par corrélation angulaire perturbée (CAP)

A perturbed angular correlation (PAC) study has been carried out to characterize the interactions between 111In and citric acid as ligand. G 22(∞), (the coefficient of perburbation) as function of pH and ligand to

γ-γ Perturbed angular correlation study of dense Kondo effect in Ce compounds

Abstract The relaxation of Ce 4f spins due to the Kondo effect was studied by γ - γ perturbed angular correlations of 140 Ce in (La-Ce)Si 2 , (La-Ce)Si 1.8 and (La-Ce)Al 2 . The deduced T K has a weak dependence on Ce concentration showing the single site character of the effect.

γ-γ Perturbed Angular Correlation Study of Ionic Motion in Silver Compound Superionic Conductors

The ionic motion in superionic conductors, Ag 2 S, Ag 2 Se and Ag 2 SI was investigated by the γ-γ perturbed angular correlations (PAC) of 111 Cd. Based on the jump diffusion model, the jump time of Ag + ions was deduced from the relaxation rate of PAC. The obtained jump time was found to be 2–150 ps and to increase in order of Ag 2 S, Ag 2 Se and Ag 2 SI. The Arrhenius plot of the jump time gives almost the same activation energy as that for the diffusion constant. This indicates the flight path remains unchanged in the measured temperature range.

Gamma rays in 148Sm from the decay of 148Eu and the 146Nd( alpha,2n gamma ) reaction.

High resolution singles and coincidence measurements have been made on gamma rays from the decay of /sup 148/Eu. On the basis of extensive ..gamma..-..gamma.. coincidence data, several new placements for transitions have been found. In addition, new weak ..gamma.. rays have been discovered. The present study has produced a revision of the previously proposed decay schemes for almost every level above the first four excited states. Previously reported levels at 1972, 2173, 2208, 2313, 2633, 2647, and 2752 keV have been discarded for lack of confirmatory evidence. New levels are proposed at 2128, 2532, 2584, 2702, and 2727 keV. For levels at 1733, 1895, 2031, 2096, 2111, 2147, 2214, 2228, 2327, 2490, 2524, 2641, 2723, 2802, and 2831 keV, ..gamma..-..gamma.. angular correlation studies have been carried out on 22 cascades to confirm J/sup ..pi../ assignments and deduce mixing ratios of the transitions concerned. A complementary study of gamma rays and conversion electrons from the /sup 146/Nd(..cap alpha..,2n..gamma..) reaction at 26 MeV has been carried out. Singles, ..gamma..-..gamma.. coincidence, and ..gamma..-ray angular distribution measurements were made to provide information on high-spin states in the /sup 148/Sm nucleus.

Perturbed angular correlation studies of the oxidation of implanted 111In in F.C.C. metals

The oxidation of 10 12 radioactive 111In ions implanted at 500 keV into the f.c.c. metals silver, copper, aluminium and platinum was studied with the perturbed angular of the induced radiation damage the metals were isochronally heated in oxygen at 200 mbar and at an oxidation temperature T ox of 300–1200 K. In all cases we found 111In in two microsurroundings: regular cubic lattice sites and InO complexes. For aluminium, silver and platinum the PAC parameters suggest a similarly structured object, where the InO bond length is proportional to the metal-oxygen bond length of the corresponding metal oxide. Temperature-dependent PAC parameters for copper were tentatively attributed to the reaction Cu→Cu 2O→CuO. Comparison of the present data with recent PAC results on 111InInO 3 excludes precipitation of In 2O 3 in the investigated cases.