This article presents numerical studies of possible of SiOH groups in "wet" SiO2 glass with 193nm laser irradiation. Structural changes associated with two conformations are presented: two nearby hydrogen bonded SiOH groups; and oxygen triclusters, i.e.e bridging oxygen forming a third covalent bond with a hydrogen atom. The energies of these two systems and the activation barrier of thermal relaxation between them identify the latter conformation as a candidate for a product formed under 193nm laser exposure, when we consider the former conformation as an initial state. The effects of local volume changes associated with the changes in conformation are investigated and it was found that it has non-eligible effects on the index of refraction.
