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 obser vation of strongly enhanced extended red emission (ERE) by interstella r dust in H-2 photodissociation zones. The ERE has been attributed to photoluminescence by hydrogenated amorphous carbon (HAC). We are demon strating that exposure to thermally dissociated atomic hydrogen will r estore the photoluminescence efficiency of previously annealed HAC. Al so, pure,amorphous carbon (AC), not previously photoluminescent, can b e induced to photoluminesce by exposure to atomic hydrogen. This conve rsion of AC into HAC is greatly enhanced by the presence of UV irradia tion. The presence of dense, warm atomic hydrogen and a strong UV radi ation field are characteristic environmental properties of H-2 dissoci ation zones. Our results lend strong support to the HAC photoluminesce nce explanation for ERE.