DENSIFICATION PROCESS IN SILICA SOL-GEL : MONITORING BY OPTICAL AND RAMAN SPECTROSCOPY B. ANDRIANASOLO, M. FERRARI, A. MONTEIL, E. DUVAL, A. SERUGHETTI, R. CAMPOSTRINI, G. CARTURAN, M. MONTAGNA et F. ROSSI J. Phys. IV France, 01 C7 (1991) C7-501-C7-504 DOI: 10.1051/jp4:19917132