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

High Resolution Image Download MS PowerPoint Slide As part of our ongoing efforts to evaluate solid para -H 2 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 (C 32 H 14 ), a medium-sized planar PAH with D 2 h symmetry, in solid para -H 2 and reassigned the previously reported S 1 –S 0 spectral features to the S 2 –S 0 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 -H 2, approximately 1650 cm –1 below the previously reported S 2 –S 0 origin at 21 050 cm –1, and a short fluorescence lifetime of ∼10 ns. We assigned these new features to the S 1 –S 0 transition based on quantum-chemical calculations at the TD-B3LYP-D3BJ/6-311++G(2d,2p) level and Franck–Condon Herzberg–Teller simulations.