A Comparison of Different Theoretical Models of Positron Lifetime Spectra for Polymers

Abstract

The same reference positron lifetime spectra of polyurethane, measured in temperature range 112 to 390 K, were analyzed with three theoretical models: the "conventional" model with three exponential decay component of discrete values of lifetimes, a model with one discrete exponential component and two "packages" of exponentials with log-normal distribution of annihilation rates, and a model considering positronium slow localization, positronium internal relaxation as well as "delayed" formation of positronium. It turns out that the two latter models fit to the experimental data with the same excellent quality, in spite of the fact that in both models the ratio of intensities related to para-positronium and ortho-positronium was constrained to be as 1:3.

Positron Lifetime Reveals the Nano Level Packing in Complex Polysaccharide-Rich Hydrolysate Matrixes

“…Positrons which have left the blob annihilate without Ps formation as e + with a lifetime τ 2 (τ 1 < τ 2 < τ 3 ). For the analysis of the positron lifetime spectra, the routine LifeTime, version 9.0 (LT9.0) , was employed.…”

Conceptual Approach to Renewable Barrier Film Design Based on Wood Hydrolysate

“…Calculations are based on a modern routine LifeTime, version 9.0 (a calculation routine for fitting the data) and the following equations to estimate the positron lifetime spectrum s ( t ): s false( t false) = I 1 normalλ 1 .25em exp false( − normalλ 1 t false) + ∑ i = 2 , 3 I i ∫ 0 ∞ normalα i false( normalλ false) normalλ .25em exp false( − normalλ t false) d normalλ 1.0em with 1.0em ∑ i = 1 , 2 , 3 I i = 1 and normalα i false( normalλ false) normalλ d normalλ = 1 normalσ i * false( 2 normalπ false) 1 / 2 .25em exp [ − ( ln λ / λ i 0 ) 2 2 σ i * 2 …”

Free volume investigation of imidazolium ionic liquids from positron lifetime spectroscopy

“…Since the hole size distribution follows a thermal statistical law, the  3 (=1/ 3 , is annihilation rate) behaves as a distribution. Mean < 3 > and its deviation 3 can be obtained from the software LifeTime 9.0 [34] by decomposing the original spectrum s(t) of the PALS measurement:…”