Abstract
The multiphoton (one-colour) excitation spectrum of jet-cooled 4-H-1-benzopyrane-4-thione (BPT) is investigated in the wavelength region from 570 to 640 nm. The emission from BPT after multiphoton excitation was detected in two wide ranges in the blue (≈ 400–500 nm) and the near UV (≈ 250–400 nm). Resonance-enhanced excitation via the first excited triplet state S 0 → T 1 → ψ ′ S,T is observed. The time dependence of the luminescence shows two components: (i) a fast decay component ( τ f < 50 ns), whose main part is assigned to S 2 → S 0 fluorescence after two-photon excitation; (ii) a slow component ( τ s ≈ 2 μ s) which may be attributed to the emission from a photofragment (CS ∗ ), efficiently created in a metastable triplet state by a four-photon absorption.
Published Version
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