Excitation of positronium from 2S to 20P state

TL;DR

This paper reports the experimental observation of positronium atoms excited from the 2S to 20P states, enabling precise velocity and line-shape analysis crucial for high-accuracy spectroscopic measurements.

Contribution

It introduces a method to excite positronium to high Rydberg states and accurately measure their velocity distribution for systematic uncertainty reduction.

Findings

Successful excitation of positronium to the 20P state.

Measurement of positronium velocity distribution via time-of-flight.

Improved modeling of line-shape considering second order Doppler shift.

Abstract

We report the observation of positronium excitation from the 2S to the 20P state. The Rydberg positronium atoms fly a distance of 40 mm before being field ionized and detected in a micro-channel plate. The time of flight can thus be measured and the velocity distribution of the atoms excited in the 2S state is reconstructed. This is used as an input to the model of the line-shape in order to properly take into account the second order Doppler shift which is the main systematic uncertainty in the 1S-2S measurements of positronium.