DIRECT DETERMINATION OF EXTINCTION COEFFICENTS FOR TRIPLET[-TRIPLET TRANSITIONS IN NAPHTHALENE, PHENANTHRENE, AND TRIPHENYLENE

Extinction coefficients for triplet ← triplet absorption have been directly determined for several aromatic hydrocarbons. A high intensity photolysis lamp was used to populate the triplet state and the concentration of triplets was measured by monitoring the depletion of the ground state. The values of the extinction coefficients ε × 10-4 (1. mol-1 cm-1) and their estimated uncertainties at the most prominent maximum λ(nm) are: naphthalene-h8, 4.0 ± 0.6, 414.0; naphthalene-d8, 4.0 ± 0.6, 414.0; phenanthrene-h10, 3.8 ± 0.6, 492.5; phenanthrene-d10, 3.1 ± 0.5, 492.5; triphenylene-h12, 1.56 ± 0.23, 430.0; and triphenylene-d12, 1.20 ± 0.18, 431.0. For anthracene, εT ≥ 9 × 104 1. mol-1 cm-1 at 427.3 nm.