Abstract
We demonstrate the laser excitation of the state of positronium (Ps) in vacuum. A combination of a specially designed pulsed slow positron beam and a high-efficiency converter target was used to produce Ps. Its annihilation was recorded by single-shot positronium annihilation lifetime spectroscopy. Pulsed laser excitation of the level at a wavelength nm was monitored via Ps photoionization induced by a second intense laser pulse at nm. About 15% of the overall positronium emitted into vacuum was excited to and photoionized. Saturation of both the excitation and the following photoionization was observed and explained by a simple rate equation model. The positronium's transverse temperature was extracted by measuring the width of the Doppler-broadened absorption line. Moreover, excitation to Rydberg states and 16 using as the intermediate level was observed, giving an independent confirmation of excitation to the state.
- Received 25 September 2015
- Revised 31 May 2016
DOI:https://doi.org/10.1103/PhysRevA.94.012507
This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society