Microwave-optical double resonance spectroscopy. Progress report, February 1, 1973--January 31, 1974

Abstract

Significant advances in the application of microwave-optical double resonance (MODR) techniques to the study of the structural properties of thc phosphorescent triplet states of organic molecules were made. Results are reported of the application of such techniques to a variety of prototype triplet states including 1,4-dihalobenzenes, 1,2,4,5-tetrahalobenzenes, naphthalene and its halogenated derivatives, and benzophenone and several of its derivatives. In addition, measurements of the magnetic field dependence of the phosphorescence lifetimes of 1,2,4,5-tetrahalobenzenes in durene are reported, and it is shown how this information can be used to determine the field dependence of electron spin lattice relaxation times in the absence of microwaves. The adamantane matrix technique has been used for preparing a wide variety of free radicals (by x-irradiation) and for obtainlng their EPR, optical absorption and emission spectra. Classes of radicals investigated include alkyl, 2-alkanonyl, allyl, and aromatic free radicals, and the information obtained from these studies includes (1) a quantitative assessment of the role of resonance stabilization in 2- alkanonyl radicals, (2) values of the kinetic and thermodynamic parameters governing both hindered rotation and ring conformational interconversions in well over fifty different free radicals whose EPR 17/O hyperfine splitting constants of a number of these species and (4) the room temperature optical emission and absorption spectra of several free radicals. (auth)