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The Excited‐State Decay of 1‐Methyl‐2(1 H )‐pyrimidinone is an Activated Process
Author(s) -
Ryseck Gerald,
Schmierer Thomas,
Haiser Karin,
Schreier Wolfgang,
Zinth Wolfgang,
Gilch Peter
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201001063
Subject(s) - intersystem crossing , excited state , fluorescence , ultrafast laser spectroscopy , internal conversion , singlet state , absorption (acoustics) , chemistry , triplet state , ground state , spectroscopy , photochemistry , time resolved spectroscopy , singlet fission , analytical chemistry (journal) , absorption spectroscopy , fluorescence spectroscopy , atomic physics , materials science , spectral line , physics , optics , quantum mechanics , astronomy , chromatography , composite material
The photophysics of 1‐methyl‐2(1 H )‐pyrimidinone (1MP) dissolved in water is investigated by steady‐state and time‐resolved fluorescence, UV/Vis absorption, and IR spectroscopy. In the experiments, excitation light is tuned to the lowest‐energy absorption band of 1MP peaking at 302 nm. At room temperature (291 K) its fluorescence lifetime amounts to 450 ps. With increasing temperature this lifetime decreases and equals 160 ps at 338 K. Internal conversion (IC) repopulating the ground state and intersystem crossing (ISC) to a triplet state are the dominant decay channels of the excited singlet state. At room temperature both channels contribute equally to the decay, that is, the quantum yields of IC and ISC are both approximately 0.5. The temperature dependence of UV/Vis transient absorption signals shows that the activation energy of the IC process (2140 cm −1 ) is higher than that of the ISC process (640 cm −1 ).