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Issue 19, 2019
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Kasha's rule: a reappraisal

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This work revises some anomalous cases reported in the literature, which seemingly violate Kasha's rule. To the contrary, apart from azulene, the remaining molecules fulfill Kasha's rule. Kasha's rule must be stated just as in the seminal paper (M. Kasha, Discuss. Faraday Soc., 1950, 9, 14–19): “The emitting electronic level of a given multiplicity is the lowest excited level of that multiplicity”. Therefore, Kasha's rule focuses on the emission (photophysics) for complex molecules, in condensed phase, for the absorption of one photon per molecule under photostationary conditions, then a rapid internal conversion and a vibrational relaxation warrant that the corresponding emission comes from the first excited electronic level regardless of which electronic state of equal multiplicity is excited.

Graphical abstract: Kasha's rule: a reappraisal

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The article was received on 06 Feb 2019, accepted on 23 Apr 2019 and first published on 23 Apr 2019

Article type: Paper
DOI: 10.1039/C9CP00739C
Phys. Chem. Chem. Phys., 2019,21, 10061-10069

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    Kasha's rule: a reappraisal

    J. C. del Valle and J. Catalán, Phys. Chem. Chem. Phys., 2019, 21, 10061
    DOI: 10.1039/C9CP00739C

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