New Electronic Transition of Ovalene in Solid para -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 para-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 D2h symmetry, in solid para-H2 and reassigned the previously reported S1-S0 spectral features to the S2-S0 transition with a lifetime of ∼1.7 μs (Weber, I., J. Phys. Chem. Lett. 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 para-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.