CONSECUTIVE CAPTURES OF ELECTRONS AND POSITRONS IN THE POSITRON SPUR BY ORGANIC HALOGENATED COMPOUNDS AND HALIDE DETACHMENT IN POLAR-SOLVENTS

The existence of fast successive captures of quasi-free electrons and then of positrons, previously evidenced with HgCl2 in various polar solvents, is confirmed in methanol and in dioxane for a variety of organic halogenated compounds (RX = CCl4, CHCl3, CH2Cl2, CH2I2, and CH3I) by combining the two independent techniques of lifetime spectroscoy and Doppler (DBARL). In methanol, the DBARL parameters characteristic of the [RX-e+] bound states are significantly different from those related to the corresponding halide ion bound state, [X-e+), indicating that no fast halide detachment occurs from RX- after electron capture by RX. For a given halo compound in a specified solvent, the constants for the inhibition of positronium formation by the solute and for the positron bound-state formation are very close. On the basis of a simple probabilistic approach, it is shown that this indicates that only one among the spur electrons is able to reach the positron to form positronium.