Seeking celestial Positronium with an OH-suppressed diffraction-limited spectrograph

TL;DR

This paper proposes a novel diffraction-limited spectrograph with OH suppression to observe positronium's electronic transitions in the near IR, aiming to detect its recombination spectrum beyond gamma-ray emissions.

Contribution

It introduces a new spectroscopic system combining photonic components to observe positronium in the near IR, overcoming atmospheric OH emission interference.

Findings

Designed a diffraction-limited spectrograph with OH suppression.

First proposed observation of positronium's Balmer alpha line at 1.3122 microns.

Potential to detect positronium's electronic transitions in space.

Abstract

Celestially, Positronium (Ps), has only been observed through gamma-ray emission produced by its annihilation. However, in its triplet state, a Ps atom has a mean lifetime long enough for electronic transitions to occur between quantum states. This produces a recombination spectrum observable in principle at near IR wavelengths, where angular resolution greatly exceeding that of the gamma-ray observations is possible. However, the background in the NIR is dominated by extremely bright atmospheric hydroxyl (OH) emission lines. In this paper we present the design of a diffraction-limited spectroscopic system using novel photonic components - a photonic lantern, OH Fiber Bragg Grating filters, and a photonic TIGER 2-dimensional pseudo-slit - to observe the Ps Balmer alpha line at 1.3122 microns for the first time.