POSITRONIUM FORMATION IN AQUEOUS-SOLUTIONS OF SURFACTANT SUBSTANCES

Investigating the behaviour of positronium atoms in the solutions of surface actant (SA) substances Jean and Ache [Jean Y.-C. and Ache H. J. (1978) J. Am. Chem. Soc. 100, 984] have observed a drastic decrease in the intensity I(ortho) of long-lived ortho-positronium component of Ps atoms when the concentration of SA molecules attains the critical value at which the micelle formation begins. This decrease is up to 1/3 from initial I(ortho) value and takes place irrespectively to the sign of electric charge of arising micelles. The aim of this communication is to give a physical interpretation and quantitative description of the discussed effect based on the model of Ps formation in liquids by combination of positron with one of the quasifree but yet nonsolvated electrons knocked out by positron during its slowing down process, It is shown that the decrease of I(ortho) and positronium formation probability P(Ps) is a result of the space segregation of quasifree electrons (e-) and positron at the end part of its track containing micelles. According to the sign of its electric charge the micelles are able to accept electrons or positron, making their interaction weaker and thus preventing the Ps formation. The calculations show that the decrease of P(Ps) (and I(ortho)) may be about several tens of per cent in accordance with available experimental data.