Single crystals of 4-choloromethyl pyridinium chloride were investigated between 123 and 300 K by the electron paramagnetic resonance method after being damaged at 296 K by γ -irradiation. The paramagnetic species was attributed to the cation radical.The principal values of the hyperfine coupling tensor of the unpaired electron with these ring atoms, and the principal values of the g tensor were determined. The results were found to be in good agreement with the existing literature data and theoretical predictions.

The electron paramagnetic resonance of γ -irradiated single crystal of tetra-N-butylammonium iodide has been studied for different orientations of the crystals in a magnetic field. The radical produced by gamma irradiation has been investigated at 300 K. The spectra were found to be magnetic field dependent and radiation damage centers were attributed to the (C α H 2 C β H 2 C γ H 2 CH 3 ) radical. The principal values of the hyperfine coupling tensor of the unpaired electron with these atoms and the principal values of the gtensor were determined and the hyperfine coupling constants were verified by computer simulation. The results were found to be in good agreement with the existing literature data and theoretical predictions.

The cholesteryl benzoate compound has been irradiated with 60 Co-γ rays at room temperature. The irradiated samples have been examined for paramagnetic resonance, and in several cases the observed spectra could be identified with specific radicals. In each case the results have been considered in relation to the present knowledge of the radiation chemistry of the compound. The single crystals have been investigated between 123 and 300 K. The spectrum parameters are found to be temperature independent. Radiation damage centers are attributed to • CHCH 2 and • CHCH 2 CH 2 radicals. The g values and the hyperfine coupling constants of the unpaired electron with the protons were determined.

The electron paramagnetic resonance of γ -irradiated single crystals of three-furancarboxylic acid has been studied for different orientations of the crystals in a magnetic field. The radicals produced by γ -irradiation have been investigated between 123 and 350 K. The spectra were found to be temperature dependent, and radiation damage centers were attributed to theradical. The principal values of the g-tensor were determined. The results were found to be in good agreement with the existing literature data and theoretical predictions.

The most important challenge on the way to optimized solar cells is to make the thickness of the individual layers smaller than the diffusion length of the charge carriers, in order to keep the collection efficiency close to unity. Here, we propose ß-SiC microcrystals grown by a sol-gel based process as a promising acceptor material. The samples are characterized by optical spectroscopy and electron paramagnetic resonance (EPR). With the help of band structures for selected surface states calculated in the framework of density functional theory (DFT) a possible scenario for the observed acceptor process is discussed.