| Optically detected magnetic resonance (ODMR) has been used to study the excited states of three different systems. The magnetically active isotope of oxygen ('17)O has been used to probe the changes in the electron charge and spin density distributions in oxygen valence orbitals which occur when benzophenone is excited to its lowest triplet state. The data obtained include the ODMR and electron-nuclear double resonance spectra at both zero and high magnetic fields. New methods of analysis of zero-field ODMR spectra, appropriate when the second-order hyperfine splitting exceeds the quadrupole coupling, are described. This analysis yields the principal values of the electron fine-structure (D), oxygen hyperfine (A), and oxygen quadrupole (Q) tensors, and the orientation of their principal axes with respect to the molecular frame. It is found, consistent with expectations for an n(pi)* state, that the direction of the largest component of Q is different from that of the ground state. It is also found that the principal transverse axes of A and Q do not conform to the local C(,2v) symmetry axes of the carbonyl group. This result is interpreted to mean that the axis of the n-type oxygen 2p orbital is rotated out of the carbonyl plane, a rotation which appears to be a direct consequence of n(pi)*/(pi)(pi)* configurational mixing. In agreement with this, the principal values of D, A, and Q are different from those expected for a "pure" n(pi)* state. Other consequences of n(pi)*/(pi)(pi)* mixing, not only in benzophenone but also in the lowest triplet states of other aromatic carbonyls, are discussed.;Attempts are also made to study the luminescent state of the Ru(bipyridyl)(,3)('2+) cation. Attempts to grow single crystals of Ru(bpy)(,3)SO(,4) are described. Emission spectra, obtained in alcoholic glasses, are broad and featureless, unlike those in the literature. Attempts were made to obtain zero-field ODMR spectra, but no signals were observed.;The lowest triplet state of 1,5-diiodonaphthalene (DIN) has also been studied by ODMR spectroscopy in order to further examine the spin-orbit coupling effects caused by the presence of two heavy atoms. Zero field ODMR spectra and phosphorescence lifetime measurements are obtained. The possible spin-orbit coupling routes to other excited states and the ground state are examined. Even though the ODMR spectra are not of optimal quality, and the lifetime data are not complete, enough inferences can be made from the data in order to discuss the lowest triplet state of DIN in terms of two possible energy level orderings for the electron spin sublevels, and a tentative choice of the sublevel ordering is made. |
