Originally published in 1967, this volume contains the proceedings of the first international conference held to discuss the triplet state and the various physical phenomena known to be associated with molecules having orbital electrons with parallel spins, and techniques for their investigation. A number of results and ideas in the field of magnetic resonance and phosphorescence of the triplet state are reported for the first time. The topics covered are spin-orbit coupling, intersystem crossing, magnetic resonance, magnetic interactions, photochemistry, radiationless transitions, triplet...