Photoinduced Penning-type ionization in collisional Rydberg carbon-molecules complexes: Energetic plausibility under interstellar conditions

Abstract

The energetic plausibility of photoinduced Penning-type ionization in collisional complexes between high-n Rydberg carbon atoms (C*s) and small molecules, such as CO and OH, is assessed. Experimental ionization potentials and vibrational constants of CO yield two transitions at 450.23 ± 0.04 nm and 498.33 ± 0.05 nm, for v = 0 and 1, respectively, while the ionization potential and spectroscopic constants of OH give rise to transitions at 705.57 ± 0.15 nm and 712.56 ± 0.15 nm, corresponding to the 2Π3/2 and 2Π1/2 states of OH. These predicted wavelengths closely match diffuse interstellar bands observed at 450.18, 498.47, 706.08, and 711.99 nm, suggesting that C* collisional complexes with interstellar molecules may contribute to selected astrophysical absorption features. Taken together, these results suggest an energetically plausible and physically motivated connection between Rydberg-mediated interactions and selected spectroscopic features under interstellar conditions, particularly in regions where C+ recombination and CO or OH coexist. Although direct experimental detection of such transient complexes has not yet been achieved, the convergence of energetic feasibility, spectral alignment, and environmental plausibility defines a testable framework. Continued progress in many-body theory, ultrahigh-resolution spectroscopy, and astronomical observations will be essential to further constrain the role of Rydberg complexes in interstellar chemistry.