Diffusion and Reactions of Hydrogen in [Formula presented]-Laser-Irradiated [Formula presented] Glass

The diffusion and reactions of hydrogenous species generated by single-pulsed [Formula presented] laser photolysis of SiO-H bond in [Formula presented] glass were studied in situ between 10 and 330 K. Experimental evidence indicates that atomic hydrogen ([Formula presented]) becomes mobile even at temperatures as low as [Formula presented]. A sizable number of [Formula presented] dimerize by a diffusion-limited reaction into molecular hydrogen ([Formula presented]) that may migrate above [Formula presented]. Activation energies for the diffusion, inherently scattered due to the structural disorder in glass, are separated into three bands centered at [Formula presented] for free [Formula presented], [Formula presented] presumably for shallow-trapped [Formula presented], and [Formula presented] for [Formula presented].