ANGULAR CORRELATION OF ANNIHILATION RADIATION FROM POSITRONS DECAYING IN SEVERAL SUBSTANCES

1951 ◽  
Vol 29 (4) ◽  
pp. 325-335 ◽  
Author(s):  
J. B. Warren ◽  
G. M. Griffiths
Keyword(s):  
Electronic Structure ◽  
Angular Correlation ◽  
Counting Rate ◽  
Alkali Halides ◽  
Chemical Compounds ◽  
The Other ◽  
Annihilation Radiation ◽  
Coincidence Counting ◽  
Coincidence Counting Rate ◽  
Angular Departure

Using anthracene scintillation counters in coincidence, the angular correlation between annihilation quanta produced by the decay of positrons in the following materials has been measured: the pure elements Mg, S, Cu, Sn, Pt, and Hg, and the chemical compounds LiCl, KCl, CsCl, KF, and KI.Calculations were performed to determine the effect of the geometry on the shape of the angular correlation curves, and the effects of scattering were investigated.The curves for copper, platinum, and possibly mercury could be approximated to by the expression[Formula: see text], where C(θ) is the coincidence counting rate as a function of θ, the angular departure of the two quanta from collinearity, and K and θ0 are constants. The curves for the other materials are more complicated and suggest that there is a relation between the shape of the curves and the outer electronic structure of the atoms with which the positrons annihilate. In alkali halides the positrons appear to annihilate only against the outer electrons of the negatively charged halogen ions.

Electronic Structure via 1D Electron Momentum Densities

2010 ◽  
Vol 666 ◽  
pp. 142-146
Author(s):  
G. Kontrym-Sznajd ◽  
M. Samsel-Czekała ◽  
S. Kaprzyk
Keyword(s):  
Electronic Structure ◽  
Compton Scattering ◽  
Angular Correlation ◽  
Annihilation Radiation ◽  
Electron Densities ◽  
Electron Momentum ◽  
One Dimensional ◽  
Crystal Orientations ◽  
Scattering Spectra ◽  
Extended Zone

We demonstrate what kind of information about the electronic structure one can get from plane projections of electron densities. As an example we use one dimensional (1D) angular correlation of annihilation radiation (ACAR) and Compton scattering spectra for Cd “measured” only for two crystal orientations. Spectra are interpreted in terms of reconstructed 2D densities both in the reduced and extended zone schemes.

scholarly journals Temperature Dependent Seasonal Variation of the Background in Counters Used for Radiocarbon Dating

Radiocarbon ◽  
1980 ◽  
Vol 22 (2) ◽  
pp. 448-454 ◽  
Author(s):  
Sören Håkansson
Keyword(s):  
Atmospheric Pressure ◽  
Counting Rate ◽  
Regression Line ◽  
Outdoor Temperature ◽  
Temperature Dependent ◽  
Coincidence Counting ◽  
Background Values ◽  
Coincidence Counting Rate ◽  
Pressure Dependency ◽  
The One

All background values measured in one of our 14C counters during 1977 were analyzed together with corresponding values for atmospheric pressure, outdoor temperature, and coincidence counting rate for investigation of the possibilities to separate the temperature dependency of the background from the better known atmospheric pressure dependency.The background values were normalized to a common atmospheric pressure and plotted in a time diagram. A seasonal trend with higher background values in winter than in summer shown by this diagram was confirmed by regression analysis.The regression line and the “Standard error of estimate” was calculated for the background values as a function of the atomspheric pressure, on the one hand and as a function of the coincidence counting rate, on the other hand. A comparison showed that the coincidence counting rate in this case was a better parameter than the atmospheric pressure for calculation of the actual background.The approximate consistency of the temperature effects on the background was checked for the years 1976 to 1978.

Two-dimensional angular correlation study of delocalized positronium in alkali halides

1997 ◽  
Vol 9 (50) ◽  
pp. 11239-11246 ◽  
Author(s):  
Yasuyoshi Nagai ◽  
Haruo Saito ◽  
Yasuyuki Nagashima ◽  
Nobuhiko Kobayashi ◽  
Toshio Hyodo
Keyword(s):  
Angular Correlation ◽  
Alkali Halides ◽  
Correlation Study ◽  
Two Dimensional

Why is the perceptual octave stretched? An account based on mismatched time constants within the auditory brainstem

2021 ◽  
Author(s):  
Alain de Cheveigné
Keyword(s):  
Time Constant ◽  
Auditory Brainstem ◽  
The Other ◽  
Inhibitory Synapses ◽  
Coincidence Counting ◽  
Time Constants ◽  
Direct Pathway ◽  
Lower Tone ◽  
Excitatory And Inhibitory Synapses

This paper suggests an explanation for listener’s greater tolerance to positive than negative mistuning of the higher tone within an octave pair. It hypothesizes a neu- ral circuit tuned to cancel the lower tone, that also cancels the higher tone if that tone is in tune. Imperfect cancellation is the cue to mistuning of the octave. The circuit involves two pathways, one delayed with respect to the other, that feed a coincidence-counting neuron via excitatory and inhibitory synapses. A mismatch between the time constants of these two synapses results in an asymmetry in sen- sitivity to mismatch. Specifically, if the time constant of the delayed pathway is greater than that of the direct pathway, there is a greater tolerance to positive than to negative mistuning, which can lead to a perceptual“stretch” of the octave. The model is applicable to both harmonic and – with qualification – melodic oc- taves. The paper describes the model and reviews the evidence from auditory psychophysics and physiology in favor – or against – it.

Angular Correlation of Positron Annihilation Radiation from Single Crystals of Vanadium-Deuterium Alloys

1979 ◽  
Vol 46 (2) ◽  
pp. 481-487 ◽  
Author(s):  
Masayuki Hasegawa ◽  
Shu-ichi Koike ◽  
Makoto Hirabayashi ◽  
Hajime Asano ◽  
Toshiharu Suzuki
Keyword(s):  
Single Crystals ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
Annihilation Radiation
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