New Electronic Transition of Ovalene in Solid <i>para</i> -H ₂ : The S ₁ –S ₀ Transition with Its Origin at 19 400 cm ^–1

As part of our ongoing efforts to evaluate solid <i>para</i>-H₂ as a matrix host for electronic spectroscopy and to explore its potential in identifying carriers of the diffuse interstellar bands (DIBs), we previously reported the electronic spectrum of ovalene (C₃₂H₁₄), a medium-sized planar PAH with <i>D</i>_2<i>h</i> symmetry, in solid <i>para</i>-H₂ and reassigned the previously reported S₁-S₀ spectral features to the S₂-S₀ transition with a lifetime of ∼1.7 μs (Weber, I., <i>J. Phys. Chem. Lett.</i> 2024, 15, 10696). Extending our investigation to lower energies, we now report a second set of spectral features, previously unobserved, with a prominent origin band at ∼19 400 cm^-1 in solid <i>para</i>-H₂, approximately 1650 cm^-1 below the previously reported S₂-S₀ origin at 21 050 cm^-1, and a short fluorescence lifetime of ∼10 ns. We assigned these new features to the S₁-S₀ transition based on quantum-chemical calculations at the TD-B3LYP-D3BJ/6-311++G(2d,2p) level and Franck-Condon Herzberg-Teller simulations.