Experimental studies of triplet exciton bands of molecular crystals

Methods of studying properties of triplet exciton states of organic crystals are presented with an emphasis on exposing the dimensionality of excitons. Results of isotopic replacement spectra for 1,4-dibromonaphthalene which is a linear chain, and for halogenated benzenes, which are likely to be linear chains, are presented. Luminescence studies of linear chain exciton systems are shown to yield information about the stationary states of small clusters. Finally some preliminary studies of two-photon spectra of naphthalene excitons are described.