Detect triplet-state PAH signatures in astronomical spectra

Determine whether existing astronomical data contain infrared signatures of polycyclic aromatic hydrocarbons in their lowest excited triplet states.

Background

The paper establishes that neutral PAHs in their lowest excited triplet states have infrared spectra that differ substantially from those of their singlet ground states, including potentially diagnostic features near 6.8 μm and in the 12–16 μm range. The authors compare calculated singlet- and triplet-state spectra with JWST/MIRI observations of the Orion Bar and note that some observed features could include contributions from triplet PAHs.

However, the presence of triplet-state PAHs in existing astronomical observations has not been established. The authors identify dedicated modeling and more comprehensive infrared databases for larger triplet PAHs as necessary steps toward resolving whether such signatures are already present and distinguishable in astronomical spectra.

References

The above argumentation raises the question of whether existing astronomical data may already contain signatures of triplet PAHs.

— Interstellar Aromatic Infrared Bands: IR absorption spectroscopy of the lowest triplet state of naphthalene  (2608.24395 - Paunikar et al., 25 Aug 2026) in Section 3, Astrophysical implications