Positron lifetime spectra as well as one-dimensional angular distributions of photons coming from the two-photon annihilation of an electron-positron pair were measured at room temperature for samples of natural tektite and hyalite. The data were used for estimation of positronium characteristics in the specimens. The characteristics were analysed in terms of parameters of pores trapping the positronium atoms before their decay. In the analysis two models of the traps were taken into account, i.e. the square potential wells of spherical symmetry with barriers of finite and infinite heights. It was found that the linear dimensions of the pores resulting from these two-trap models are almost the same and they are of the order of 1 nm.
Positron lifetime spectra as well as one-dimensional angular correlations of positron annihilation radiation were measured at room temperature for samples of rhyolitic obsidian coming from Iceland, Italy and Armenia. The samples were of different age. One specimen (originating from Iceland) was relatively young, formed in 1980. The others were much older, collected during the 19th century. It was found that the linear dimensions of pores trapping the positronium atoms before their decay as well as the pore concentration in all old obsidians are almost the same independently of the place of their formation. Simultaneously the concentration of the pores in the young sample is about five times lower than in the old specimens. Basing on the result it is suggested to extend the study in order to find out if positron annihilation can be used for the investigation of the age of the volcanic accumulations containing obsidian.
The nanostructure of several non-crystalline amber samples of different origin was investigated with positronium atoms. It was found that the volumes of the pores observed by positronium atoms are relatively small, not greater than about 0.25 nm³ for all studied samples. Moreover, the obtained data show that the nano-porous structure of amber may be associated with its age.
Studies of positron annihilation accompanied by EPR technique were undertaken for sodalite and lazurite and their synthetic counterparts (synthetic sodalite and ultramarines). Results of measurements performed by two techniques of positron annihilation spectroscopy (angular correlation of annihilation radiation, ACAR, and positron annihilation lifetime) revealed the undoubted influence of free radicals on positron annihilation mechanism but both inhibition of positronium formation by them and the effect of filling cages ought to be taken into account. The distinct differences between ACAR curves for sodalites, lazurites and ultramarines probably reflect the presence of different radicals in their cages and chemical heterogeneity as well as the disorder in Al, Si-site ordering in case of ultramarines. Comparison of the results of ACAR measurements with the ones of the EPR studies indicates that there is correspondence between them. Similarly to three families of the ACAR curves, different likes of EPR lines were obtained for three groups of samples; sodalites, lazurites and ultramarines. It is possible that the annihilation of positrons takes place mainly with unpaired electrons recorded by the EPR technique.
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