RECENT STUDIES ON TRIPLET-SINGLET TRANSITIONS IN AROMATIC MOLECULES
CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND BIOCHEMISTRY
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The paper is divided into four parts. The first part discusses the selection rules of the intersystem crossing process in systems having both n, pi and pi,pi types of states. The detection of the polarized state by observing the phosphorescence emission requires that the radiative lifetime of the latter from at least one of the three sublevels of the lowest triplet state be shorter than the characteristic time for the spin-lattice relaxation processes between the three sublevels of the triplet state. This is demonstrated to be the case for pyrazine in its n,pi triplet state at low temperatures 1.6 -10K and discussed in Section III. In the third part of the paper, a summary of the theory of the triplet-singlet radiative transitions is given. A comparison of phosphorescence properties of the different systems is made and the observed differences are explained in the framework of the present theory. In the last part of this paper, the important experiments needed in this field are recommended.
- Radiation and Nuclear Chemistry