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THE IONIZATION OF ORGANIC MOLECULAR CRYSTALS BY NEAR U.V. LIGHT *
Author(s) -
Kearns David R.
Publication year - 1964
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1964.tb08154.x
Subject(s) - photoionization , intersystem crossing , ionization , anthracene , quantum yield , excited state , chemistry , singlet fission , atomic physics , quantum , singlet state , molecular physics , physics , photochemistry , fluorescence , ion , optics , quantum mechanics , organic chemistry
Summary The niechanisms by which near u.v. light cause internal ionization in organic molecular crystals are examined theoretically for the anthracene crystal. Theoretical predictions of the quantum yield for photoionization by the various mechanisms are presented and compared with values recently obtained from studies of photoconduction in anthracene. From this comparison we conclude that: (i) Good agreement between calculated and observed quantum yields suggests that the method used for the calculations is essentially valid. (ii) Provided the energy requirements can be met, quantum yields for photoionization may approach unity. (iii) The lifetimes of excited singlet and triplet states and the rate of intersystem crossing materially influence the quantum yields for photoionization. (iv) An aggregated, but not necessarily ordered, molecular system should be capable of exhibiting quantum yields for photoionization which are as large as those which can be obtained with single crystals. The possible relevance of these results for biological systems is discussed briefly.