Deciphering the molecular origin of the 19.3 eV electronic excitation energy of H₃^.

ABSTRACT: The trihydrogen cation, H₃ ⁺, is unique in the Universe. It serves as the primary proton reservoir, driving essential astrochemical reactions, and it functions as a thermostat for giant gas planets. H₃ ⁺ has also a remarkably low photodissociation rate, explained by its exceptionally high first electronic excitation energy (19.3 eV), which is well above the ionization energy of the much more abundant monohydrogen (13.6 eV). Herein we reveal that the key factors behind the high excitation energy of H₃ ⁺, and thus, its astrophotochemical inertness, are: (i) aromatic stabilization in its electronic ground state, (ii) antiaromatic destabilization in its first excited state, and (iii) a high nuclear-to-electronic charge ratio (+3

SUBMITTER: Toldo JM 

PROVIDER: S-EPMC12817475 | biostudies-literature | 2026 Jan

REPOSITORIES: biostudies-literature