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"Ultrafast quenching of the xanthone triplet by energy transfer: New insight into the intersystem crossing kinetics" H. Satzger, B. Schmidt, C. Root, W. Zinth, B. Fierz, F. Krieger, J. Phys. Chem. A. 108 (2004) 10072-10079 Abstract: The formation and quenching of the triplet state of xanthone is studied by femtosecond techniques. As revealed by femtosecond fluorescence spectroscopy the primarily excited 1pi pi* state decays within 1.5~ps. In a transient absorption experiment this time constant is associated with a partial rise of a triplet signature. This rise has a second and slower component with a time constant of 12 ps. In the presence of high concentrations of the quencher 1-methylnaphthalene the slow 12~ps rise component is absent. This finding gives strong evidence that the bi-phasic rise of the triplet absorption of xanthone is due to a sequential mechanism, namely a 1pi pi*-3npi* with fast intersystem crossing followed by a 3npi*-3pi pi* internal conversion. Furthermore, an analysis of the concentration dependence of the quenching kinetics allows to pin down the intrinsic transfer time of the triplet energy from xanthone to 1-methylnaphthalene to ~1 ps. BMO authors (in alphabetic order): Peter Gilch Christopher Root Helmut Satzger Bernhard Schmidt Wolfgang Zinth Assoziierte Projekte: Spectroscopy of the functional dynamics of proteins Peptide and protein folding Ultrafast Intersystem Crossing in Aromatic Carbonyl Compounds |