Positronium in the 2S3 metastable state exhibits a low electrical polarizability and a long lifetime (1140 ns), making it a promising candidate for interferometry experiments with a neutral matter-antimatter system. In the present work, 2S3 positronium is produced, in the absence of an electric field, via spontaneous radiative decay from the 3P3 level populated with a 205-nm UV laser pulse. Thanks to the short temporal length of the pulse, 1.5 ns full width at half maximum, different velocity populations of a positronium cloud emitted from a nanochanneled positron-positronium converter were selected by delaying the excitation pulse with respect to the production instant. 2S3 positronium atoms with velocity tuned between 7×104ms-1 and 10×104ms-1 were thus produced. Depending on the selected velocity, a 2S3 production efficiency ranging from ∼0.8% to ∼1.7%, with respect to the total amount of emitted positronium, was obtained. The observed results give a branching ratio for the 3P3-2S3 spontaneous decay of (9.7±2.7)%. The present velocity selection technique could allow one to produce an almost monochromatic beam of ∼1×1032S3 atoms with a velocity spread of <104ms-1 and an angular divergence of ∼50 mrad.

Velocity-selected production of 2 S 3 metastable positronium

Caccia, M.;Santoro, R.;
2019-01-01

Abstract

Positronium in the 2S3 metastable state exhibits a low electrical polarizability and a long lifetime (1140 ns), making it a promising candidate for interferometry experiments with a neutral matter-antimatter system. In the present work, 2S3 positronium is produced, in the absence of an electric field, via spontaneous radiative decay from the 3P3 level populated with a 205-nm UV laser pulse. Thanks to the short temporal length of the pulse, 1.5 ns full width at half maximum, different velocity populations of a positronium cloud emitted from a nanochanneled positron-positronium converter were selected by delaying the excitation pulse with respect to the production instant. 2S3 positronium atoms with velocity tuned between 7×104ms-1 and 10×104ms-1 were thus produced. Depending on the selected velocity, a 2S3 production efficiency ranging from ∼0.8% to ∼1.7%, with respect to the total amount of emitted positronium, was obtained. The observed results give a branching ratio for the 3P3-2S3 spontaneous decay of (9.7±2.7)%. The present velocity selection technique could allow one to produce an almost monochromatic beam of ∼1×1032S3 atoms with a velocity spread of <104ms-1 and an angular divergence of ∼50 mrad.
2019
http://harvest.aps.org/bagit/articles/10.1103/PhysRevA.99.033405/apsxml
positronium, antimatter
Amsler, C.; Antonello, M.; Belov, A.; Bonomi, G.; Brusa, R. S.; Caccia, M.; Camper, A.; Caravita, R.; Castelli, F.; Cerchiari, G.; Comparat, D.; Conso...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/2077827
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