Producing long-lived $2^3\text{S}$ Ps via $3^3\text{P}$ laser excitation in magnetic and electric fields

TL;DR

This study demonstrates the production of long-lived positronium in the $2^3S$ state through laser excitation to the $3^3P$ level, using magnetic and electric fields, with a novel analysis of annihilation spectra.

Contribution

It introduces a new method to produce and detect long-lived positronium in the $2^3S$ state via laser excitation and a novel spectral analysis technique.

Findings

Positronium in $2^3S$ state achieved with 2.1% efficiency.

Use of UV laser pulse in magnetic and electric fields for excitation.

Novel analysis technique for positronium lifetime spectra.

Abstract

Producing positronium (Ps) in the metastable $2^3\text{S}$ state is of interest for various applications in fundamental physics. We report here about an experiment in which Ps atoms are produced in this long-lived state by spontaneous radiative decay of Ps excited to the $3^3\text{P}$ level manifold. The Ps cloud excitation is obtained with a UV laser pulse in an experimental vacuum chamber in presence of guiding magnetic field of 25 mT and an average electric field of 300 V/cm. The indication of the $2^3\text{S}$ state production is obtained from a novel analysis technique of single-shot positronium annihilation lifetime spectra. Its production efficiency relative to the total amount of formed Ps is evaluated by fitting a simple rate equations model to the experimental data and found to be $ (2.1 \pm 1.3) \, \% $.