Positronium chemistry

Schrader, D. M. Jean, Y. C. 1988. Positron and Positronium Chemistry. Elsevier, Amsterdam, The Netherlands. 

Jean, Y.C., DM. Schrader, and P.E. Mallon Principles and Applications of Posttron and Positronium Chemistry, World Scientific Publishing Company, Inc.,... 

Proceedings of the International Workshop on Positron and Positronium Chemistry edited by D.M. Schrader and Y.C. Jean, Elsevier Science, Amsterdam (1988)... 

Proceedings of the Fourth International Workshop on Positron and Positronium Chemistry (held at Le Mont Saint-Odile, France, 1993) edited by I. Billard, G. Duplatre and J.Ch. Abbe, published in Journal de Physique IV, Coll. C4, supp. Journal de Physique II 3 (1993)... 

The p-Ps has a shorter lifetime than o-Ps and it annihilates into two photons, while o-Ps annihilates into three photons. The intrinsic lifetime is 0.125 ns and 142 ns for the free p-Ps and o-Ps, respectively. In ordinary molecular media, the electron density is low enough so that Ps can pick off electrons from the media that have anti-parallel spin to that of the positron, and undergo two-photon annihilation. This is called the pick-off annihilation of Ps. The pick-off annihilation of o-Ps not only occurs in the form of two-photon annihilation, it also shortens the o-Ps lifetime from 142 ns (free o-Ps) to a few ns. The pick-off annihilation lifetime of o-Ps in molecular systems is about one order of magnitude greater than in crystalline or metallic media. Experimental determination of o-Ps lifetime is one of the most useful methods for positron and positronium chemistry. This is because o-Ps lifetime contains information about electron density, which governs the basic properties of chemical bonding in molecules. It is also controlled by the physical structure of molecules. 

Existing books and articles on positron and positronium chemistry and annihilation... 

Billard, Ed. Fourth International Workshop on Positron and Positronium Chemistry, J. De Physique, Vol. 3, Coll. N 4, Suppl. JP, n 9, Les Ulis Cedex A, France Zone Indu. De Couttaoeuf, (1993). 

Zs. Kajcsos, B. Levay, K. Suvegh, Eds. Proceedings of the 5 h International Workshop on Positron and Positronium Chemistry, J. Radioanal. Nucl. Chem., Akademiai Kiado, Budapest Elsevier Science, A (1996). 

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