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

Gordon Robertson*, Simon Ellis, Qingshan Yu, Joss Bland-Hawthorn, Christopher Betters, Martin Roth, Sergio Leon-Saval

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Celestially, positronium (Ps) has been observed only 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 near IR 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 2D pseudo-slit—to observe the Ps Balmer alpha line at 1.3122 µm for the first time, to our knowledge.

Original languageEnglish
Pages (from-to)D122-D128
Number of pages7
JournalApplied Optics
Issue number19
Publication statusPublished - 1 Jul 2021


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