Triplet Ps annihilation parameters in ethanol/ c i s -2-pentene/platinum mixtures containing platinum or platinum on charcoal

Positron lifetimes and intensities were compared, with and without external mixing, for simulated hydrogenation reaction mixtures consisting of 2/1, 1/1, 0.25/2, 0.5/2, 0.75/2, 1/2, and 1.5/2 ethanol/cis-2-pentene molar ratios to which 0.6 mg platinum powder or 5% platinum on charcoal were added. For platinum mixtures marked quenching of all o-Ps lifetimes and intensities occurred with external mixing. For 1/2 and 1.5/2 platinum-on-charcoal mixtures, the combined o-Ps intensity increased from 66% to 76% and from 30% to 76%, respectively, with external mixing.