Photoacoustic and transmission spectroscopies on the effect of heat treatment in Na colloids in an electron-irradiated NaCl crystal

Abstract

Thin crystals of NaCl were deeply colored by intense electron irradiation and were subsequently heated at 473 K for various periods. The peak ofthe PAS spectrum due to Na⁺ clusters in the crystal is shown to agree well with the optical absorption peak in a transmission spectrum. PA signal dependence on optical density and modulation frequency reveals non-uniform distribution of metallic colloids along the crystal's depth after heat treatment. The results showed the advantages of PAS to confirm the formation of metallic colloids by high energy electron irradiation and their distribution after heat treatment.