ACTIVATION OF EXTENDED RED EMISSION PHOTOLUMINESCENCE IN CARBON SOLIDS BY EXPOSURE TO ATOMIC-HYDROGEN AND UV-RADIATION

We report on new laboratory results which relate directly to the observation of strongly enhanced extended red emission (ERE) by interstellar dust in H-2 photodissociation zones. The ERE has been attributed to photoluminescence by hydrogenated amorphous carbon (HAC). We are demonstrating that exposure to thermally dissociated atomic hydrogen will restore the photoluminescence efficiency of previously annealed HAC. Also, pure,amorphous carbon (AC), not previously photoluminescent, can be induced to photoluminesce by exposure to atomic hydrogen. This conversion of AC into HAC is greatly enhanced by the presence of UV irradiation. The presence of dense, warm atomic hydrogen and a strong UV radiation field are characteristic environmental properties of H-2 dissociation zones. Our results lend strong support to the HAC photoluminescence explanation for ERE.