Published online by Cambridge University Press: 15 February 2011
The interaction of synchrotron radiation (SR) emitted from a polarizing undulator with SiO2 gel films was investigated by ellipsometry and infrared spectroscopy. The photon energy in SR was varied in the range of 6.4−17.8 eV using an Onuki-type undulator in order to study the energy dependence of the interaction. We found that an increase of refractive index, a decrease of thickness of the films and a loss of OH groups were induced by photons with energies above ˜9 eV although any changes were not observed with photons below ˜7 eV. These results suggest that SiO2 gel films are densified through electronic processes stimulated by the energetic photons.