title: Lowest excited triplet states of hypericin and isohypericin.
abstract: The fluorescence and phosphorescence of hypericin and isohypericin were studied in an ethanol matrix at 1.2 K. The prompt fluorescence spectra are mirror images of the absorption around the 0-0 transition, as expected. The 0-0 vibronic lines of the phosphorescence are found at 13,190 and 13,622 cm-1, and the phosphorescence decay times are 2.79 and 6.6 ms at 1.2 K for hypericin and isohypericin respectively. The fluorescence excitation spectrum of isohypericin reveals a small trace of a different pigment, possibly a tautomeric form of isohypericin. The decay of the phosphorescence of isohypericin is biexponential. The slow component is attributed to an unknown contaminant with a high quantum yield of phosphorescence.
authors.affiliation: 3. Physikalisches Institut, Universität Stuttgart, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Angerhofer
authors.forename: H
authors.initials: H
authors.lastname: Falk
authors.forename: J
authors.initials: J
authors.lastname: Meyer
authors.forename: G
authors.initials: G
authors.lastname: Schoppel
mesh_terms: D000873:Anthracenes; D003080:Cold Temperature; D007536:Isomerism; D007700:Kinetics; D008163:Luminescent Measurements; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D011838:Radiation-Sensitizing Agents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D000873:Anthracenes; D011838:Radiation-Sensitizing Agents; D010569:Perylene; C004965:hypericin