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V. I. Goldanskii A. D. Mokrushin A. O. Tatur V. P. Shantarovich 《Applied Physics A: Materials Science & Processing》1975,5(4):379-382
Positronium interaction with O2, NO, Cl2 molecules in pores of silicagels has been investigated by the methods of lifetime and angular correlation. For silicagel with diameter of pores ≈100 Å it was obtained that the rate constant of positronium conversion on oxygen was (2.4±0.2)107 sec?1 atm?1 and on nitrogen oxide (2.6±0.2)107 sec?1 atm?1. The rate constant of the positronium chemical reaction with Cl2 was found to be ≈10?11 sec?1 atm?1. The results of investigation of positronium interactions with oxygen in the gas phase, organic liquids, zeolites, liquid argon, and nitrogen are explained in terms of the formation of an excited complex PsO 2 * . The decay of this complex to Ps and O2 makes possible positronium conversion, and stabilization of the complex leads to annihilation in the bound state (chemical reaction). Study of positronium interaction with O2 in silicagels (diameters of pores 100, 30 and 16 Å) confirms the assumption of the complex formation. The rates of chemical reaction and of conversion become equal for pores of diameter of 20 Å. The estimated lifetime of the PsO 2 * complex is τ k ? 10?12 sec. 相似文献
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V. P. Shantarovich T. Suzuki Yu. P. Yampol’skii P. Budd V. V. Gustov I. B. Kevdina A. V. Pastukhov S. S. Berdonosov V. E. Bozhevol’nov 《High Energy Chemistry》2007,41(5):370-380
Determination of the size distribution of free-volume holes in solids, in particular, polymers, is an important physicochemical problem. The positron annihilation technique has been proposed for this purpose. The central point in this technique is the quantitative interpretation of data, especially, for substances with a high specific surface area. A developed free-volume system in open-pore membrane materials, such as poly(trimethylsilylpropyne) PTMSP and the spirocyclically bound benzodioxane polymer PIM-1, and polymeric sorbents (hypercrosslinked polystyrenes) makes it possible for the first time to compare the sorption characteristics and positron annihilation data on the character of size distribution of nanopores in these polymers. In combination with the results of mathematical simulation of the structure and radiothermoluminescence measurements, the array of data indicate the structural inhomogeneity of the test amorphous materials. It was shown that this inhomogeneity in relation to the positron annihilation technique is expressed in the insufficiency of the representation of the orthopositronium decay curve by one component that takes into account the Gaussian lifetime distribution (symmetrical pore size distribution) and in the necessity of use of several decay components. The feasibility of revealing a nonrandom character of pore size distribution gives the positron annihilation technique an advantage over other approaches (inverse gas chromatography, 129Xe NMR) to investigation of nanopores in polymers. 相似文献
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Russian Chemical Bulletin - 相似文献
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V. P. Shantarovich V. W. Gustov E. V. Belousova A. V. Polyakova V. G. Bekeshev I. B. Kevdina 《Russian Journal of Physical Chemistry B, Focus on Physics》2014,8(4):559-565
Polymeric membrane materials with highly developed intrinsic microporosity for gas separation are studied. The porosity can be essentially improved by filling the polymer with nonorganic components (zeolites). This porosity, herein referred to as artificially induced, turned out, in some cases, to be higher than that of the constituent components. The reasons for this effect are not always clear. To gain additional insights into the nature of this effect, an experimental study is suggested with the use of a combination of two methods related by being based on track processes: positron annihilation lifetime spectroscopy PALS and thermostimulated luminescence (TSL). The present paper summarizes and discusses both recently published results and completely new data. 相似文献
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Ch. He E. Hamada T. Suzuki H. Kobayashi K. Kondo V. P. Shantarovich Y. Ito 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):431-435
A new pulsed mono-energetic slow positron beam as well as the conventional positron annihilation lifetime spectroscopy (PALS) have been applied to study the sub-surface and the bulk of epoxy polymer. Significant changes of o-Ps parameters were found at a short distance from the surface. The lifetime of o-Ps was observed to decrease with increasing the positron implantation depth, while its intensity increased. The temperature effect on o-Ps parameters at sub-surface was also investigated. The glass transition temperature for the sub-surface was lower than that for the bulk. Furthermore, the thermal expansion coefficient of the sub-surface was found smaller than that of the bulk. 相似文献
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V. I. Goldanskii Yu. A. Novikov A. V. Rakov V. P. Shantarovich 《Structural chemistry》1991,2(3-4):(135)343-(150)358
Some of the ideas and experimental results discussed in this contribution seem to demonstrate valuable possibilities for traditional angular correlation measurements of annihilation radiation in studies of laminar structures and in solving some problems of solid-state physics and technology. 相似文献
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A possibility to study the properties of substances using positronium as the simplest "labeled" atom
V. P. Shantarovich T. Suzuki C. He 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(1):165-170
A bound state of positron (e+) and electron (e-) (positronium Ps) can be considered as a kind of hydrogen-like atom and the simplest free radical, which has a positron instead of a heavy nucleus. Annihilation g-radiation is in fact a label of this short-lived atom. Therefore, positronium chemistry is radiochemistry of the lightest short-lived labeled atom. Application of positronium chemistry to various chemical problems is essentially dependent on our knowledge of analogies and differences in the formation and chemical conversion of Ps, a atomic hydrogen, and other free radicals. In this review, experimental results of the authors and some other publications are briefly analyzed from this point of view. 相似文献
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V. P. Shantarovich 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):2485-2503
In this article, the interconnections between the ortho-positronium (the bound state of the positron and electron having parallel orientation of spins, TPs) pick-off annihilation characteristics and concentration and effective size of elementary free volumes in polymer structures are discussed. Free volume parameters are responsible for many important properties of polymers such as permeability to gases, selectivity, ageing mechanical strength, etc. However, the ways of quantitative estimations of size distributions of the free volume elements on the bases of experimental data are sometime not obvious. Various approaches to this problem are analyzed in this review mostly on examples of glassy polymer membrane materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2485–2503, 2008 相似文献