Time Spectra of Positrons Annihilating in Organic Liquids Containing Halogens

Measurements have been made of the mean life τ2, and the percent I2, of positrons forming triplet positronium in propyl halides and in benzene-carbon tetrachloride solutions. The experimental variations of I2 in the propyl halides can be predicted assuming a semiempirical equation of the form 100–4/3I2=AN1+2.4N2, where A is the annihilation factor of the parent molecule and N1 and N2 are the percent volumes of the parent and halide, respectively. A equal to 0.36 is needed for the propyl parent. This equation also predicts correctly the experimental values for the benzyl halides if A equal to 0.53 is used as the benzyl annihilation factor. The quenching of I2 in the benzene-carbon tetrachloride solutions is much greater than that computed by the equation and the variation in quenching closely resembles that obtained in aqueous nitrate-ion solutions.