A noninteractive model for dual phosphorescence in aromatic carbonyls

✍ Scribed by San-Yan Chu; Lionel Goodman

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 458 KB
• Volume: 34
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(75)85261-4

✦ Synopsis

A non-interactive density of states model is presented to explain the observed anomalous dual phosphorescences of certain aromatic carbonyl compounds. Although the experiments are in rigid media the model is in terms of the free molecule.

The phenomenon of dual phosphorescence in a large molecule violates the well-known Kasha rule: emission can occur only from the lowest excited electronic state of a given multiplicity. For a small energy gap between the second triplet state (Tz) and the first triplet state (iI), the sparse density of TI vibronic levels isoenergetic with the T2 vibrationless level leads to a slow T2 --+ T, radiationless process which is unable to quench the Tz emission completely. Two cases: T1 = 3nn*, Tz = 3nrr*;

and T1 = 3rrnf, Tz = 3 nrr" are discussed at both low and high temperature limits. An impcrtant result is that raising the tsmperature in the former case is predicted to incxase the intensity cf the T, emission at the expense of the T2 emission, and conversely for ihe latler case. According to the model dual phosphorescence should also be observable in certain azines.