LOW FREQUENCY RAMAN STUDY OF THE HARMONIC VIBRATIONAL MODES IN SILICA AEROGELS J.L. SAUVAJOL, J. PELOUS, T. WOIGNIER et R. VACHER J. Phys. Colloques, 50 C4 (1989) C4-167-C4-169 DOI: 10.1051/jphyscol:1989427