An unusual three-quantum yield from positrons annihilated in benzene

Abstract

Featuresof positronsannihilated in benzene were investigated by the threegamma coincidences technique, together with lifetime spectroscopy and a magnetic quenching experiment. A high three-quantum yield was found; the result reveals the presence of two positron bound states: a 'relaxed' positronium system and a more complex one.

Positronium Formation in Organic Liquids

“…This was noticed already in pioneer experiments [14] and fully confirmed in more recent data from Milan Politecnics [23,24]. Our measurements show that in atmosphere of air the τ 3 lifetime is in-between degassed and oxygensaturated samples, see Table I (for benzene) and Fig.…”

“…1 for the latter. Presently derived lifetimes (τ 2 = 380−460 ps for all the three compounds) and intensities I 2 and I 1 at room temperature agree within uncertainties with three and four-component analysis of Consolati and co-workers [23,24] and Mogensen [15]. All these data suggest that paramagnetic quenching has no influence either on the very o-Ps formation or on the other annihilation routes.…”

Positronium Formation in Molecular Gases --- from Experiment to Modeling

“…Moreover, the present data for the second component τ 2 (about 380-400 ps) and I 2 are compatible with the results of three-and four-term analysis reported in Refs. [5,[25][26][27]. Figure 1 shows results of positron lifetimes τ 3 and τ 2 and corresponding relative intensities I 3 and I 2 as a function of temperature in non-degassed, degassed and oxygen-saturated samples of benzene (results in cyclohexane and methanol are similar).…”