Fluorine laser-induced silicon hydride Si-H groups in silica

Formation and destruction of silicon hydride (Si-H) groups in silica by F₂ laser irradiation and their vacuum ultraviolet (VUV) optical absorption was examined by infrared (IR) and VUV spectroscopy. Photoinduced creation of Si-H groups in H₂-impregnated oxygen deficient silica is accompanied by a growth of infrared absorption band at 2250 cm^-1 and by a strong increase of VUV transmission at 7.9 eV. Photolysis of Si-H groups by 7.9 eV photons in this glass was not detected when the irradiation was performed at temperature 80 K. However, a slight destruction of Si-H groups under 7.9 eV irradiation was observed at the room temperature. This finding gives a tentative estimate of VUV absorption cross section of Si-H groups at 7.9 eV as 4 × 10^-21 cm², showing that Si-H groups do not strongly contribute to the absorption at the VUV fundamental absorption edge of silica glass.