The electron resonance of ground state triplets in liquid crystal solutions

Abstract

The electron resonance spectra of two ground state triplets have been measured in the isotropic and nematic mesophase of p-azoxyanisole. The extra transitions observed when the biradicals are in the nematic mesophase are interpreted in terms of an unaveraged zero-field splitting. The nitrogen hyperfine splitting is also found to decrease in the nematic mesophase. The observation of these extra lines in the spectra provides excellent quantitative confirmation for the triplet character of these radicals. The changes in the spectra are satisfactorily accounted for using the swarm model of nematic liquid crystals.