CO2Laser Photochemical Hole Burning in the IR Reflection Spectra of Crystalline Natural Silicates

Structural and chemical transformations induced on the surface of crystalline natural silicates by pulse СО2laser radiation with a pulse length of 200 ns and an energy per pulse of 2 J were examined. The IR reflection spectra of nepheline KNa3[AlSiO4]4and rhodonite CaMn4[Si5O15] were measured before and after exposure to laser radiation. An increase in the reflectance at the laser frequency used was observed, which was named “hole burning” in the IR reflection spectra of specimens. A 50-cm–1wide hole was shown to be burnt at a frequency coinciding with that of a laser radiation line within this width. At the incident laser frequency, a narrow, 5-cm–1wide hole is also burnt in the IR spectra of the irradiated samples. The burning of the 50-cm–1hole was assumed to be due to the selective sublimation of SimOncomplexes. The burning of the narrow hole of 5 cm–1width is associated with the laser-induced selective dissociation of Si–O bonds in the near-surface layer at the frequency employed.