Triplet-Singlet Transitions in Organic Molecules. Lifetime Measurements of the Triplet State
- 1 October 1949
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 17 (10), 905-913
- https://doi.org/10.1063/1.1747085
Abstract
The emission lifetimes of the metastable triplet states (phosphorescent states) of a large variety of organic molecules have been measured. The lifetimes are in the range from 10−4 to about 10 seconds. It is shown that the transition probabilities corresponding to the shorter lifetimes are of the same magnitude as found in the light atoms of which the molecule is composed. The longer lifetimes, on the order of seconds, are found only among the aromatic compounds. A consideration of the perturbing singlet states in aromatic compounds shows that the matrix elements for the intercombination must be very much smaller than those responsible for the intercombination in the free carbon atoms. Direct evidence that the long‐lived states of the aromatic compounds are triplet states is obtained by showing that as the atomic number of chemically similar substituents is increased (e.g. substitute Br for Cl), the transition probability increases approximately in proportion to the increase in the square of the spin‐orbit interaction energy of the substituent atom. The luminescences are usually observable only when the substance is dissolved in a rigid solvent, and the effect of such a solvent on the lifetimes is discussed. Experimental data relating singlet‐triplet absorption strength to triplet state lifetime is presented.Keywords
This publication has 14 references indexed in Scilit:
- Selection Rules for Singlet-Triplet Perturbations in Polyatomic MoleculesThe Journal of Chemical Physics, 1949
- Vibrational Analysis of the 3400A Triplet-Singlet Emission of BenzeneThe Journal of Chemical Physics, 1949
- Molecular Orbital Treatment of the Ultraviolet Spectra of Benzene and BorazoleThe Journal of Chemical Physics, 1948
- Intensities of Electronic Transitions in Aliphatic Ketones in the Vacuum Ultraviolet.Chemical Reviews, 1947
- PARAMAGNETISM OF THE PHOSPHORESCENT STATEJournal of the American Chemical Society, 1945
- Phosphorescence in Fluid Media and the Reverse Process of Singlet-Triplet AbsorptionJournal of the American Chemical Society, 1945
- Phosphorescence and the Triplet StateJournal of the American Chemical Society, 1944
- The Quantum Yield of Diacetyl FluorescenceThe Journal of Chemical Physics, 1943
- Reversible Photochemical Processes in Rigid Media. A Study of the Phosphorescent StateJournal of the American Chemical Society, 1941
- Lifetime of Fluorescence in Diacetyl and AcetoneThe Journal of Chemical Physics, 1940