RT Book, Whole DB /z-wcorg/ DS http://worldcat.org ID 428078065 LA English T1 Triplet to triplet absorption in organic molecules for use in photochromic devices A1 Kropp, John L., Windsor, Maurice W., Air Force Materials Laboratory (U.S.), TRW Systems Group., PB Air Force Materials Laboratory, Air Force Systems Command, United States Air Force PP Wright-Patterson Air Force Base, Ohio YR 1968 AB The photochromic properties of several substituted aromatics and heterocyclics have been investigated. The absorption spectra, phosphorescence lifetime T-T absorption spectra and the product of triplet extinction coefficient and triplet formation efficiency, were evaluated for representative compounds. Using these data the photochromic properties of heterocyclics are compared to their hydrocarbon analogs. The values of the maximum triplet formation efficiency are lower for heterocyclics than for aromatics. However, broader T-T absorption and more efficient absorption for pumping light suggest that, on balance, heterocyclics are comparable to aromatic hydrocarbons in their effectiveness as photochromic materials. The variation of solvent induces large changes in the photochromic properties of heterocyclics thus providing a useful additional parameter for adjusting their properties. These differences also promise to shed light on the mechanism of radiationless transitions in these compounds. Recommendations for further studies to improve the photochromic properties of heterocyclics are made.