Positronium Production in Engineered Porous Silica
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- 作者：Rafael Ferragut ; Stefano Aghion ; Gaia Tosi ; Giovanni Consolati ; Fiorenza Quasso ; Mariangela Longhi ; Anne Galarneau ; Francesco Di Renzo
- 刊名：Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：December 19, 2013
- 年：2013
- 卷：117
- 期：50
- 页码：26703-26709
- 全文大小：305K
- 年卷期：v.117,no.50(December 19, 2013)
- ISSN：1932-7455
文摘
Positronium (Ps) has been the subject of several experimental and theoretical investigations due to its many scientific applications. In this work high positronium yield was found in engineered porous silica. The studied materials were pellets of swollen MCM-41 and of commercial Davicat 1700, obtained by different compression pressures, with mesopores characterized by different structural and chemical features. The measurements were performed with a variable energy positron beam at room temperature. An estimation of the Ps mean diffusion length was obtained by measuring capped samples. A selected swollen MCM-41 sample (0.39 g/cm3) was measured also at cryogenic temperature (8 K). In this material both the Ps yield and the Ps diffusion length are found to be independent of temperature. The pore surface of the swollen MCM-41 samples is very interesting in comparison to commercial silica as it possesses hydrophobic patches to avoid ice formation at low temperature. Positron lifetime measurements show a high Ps survival time inside the mesoporous materials (110 ns), which promotes a high Ps mobility during cooling inside the pores favoring diffusion lengths up to 1 渭m for swollen MCM-41 materials. Besides, it was possible to estimate the total Ps yield coming up outside the sample at high implantation energies and the time between the implantation of positrons and the Ps release.