The SiCO4 molecule has been produced by reaction between silicon dioxide and carbon dioxide molecules in solid argon. Silicon dioxide molecules were prepared by reactions of laser-ablated silicon atoms with oxygen in excess argon. When carbon dioxide molecules were added in the reagent gas, new product absorptions at 1934.9, 1326.1, 1070.2 and 866.0 cm(-1) were produced spontaneously on annealing. Based on isotopic substitution and density functional theoretical calculations, these absorptions are assigned to the vibrational fundamentals of the SiCO4 molecule that has Q, symmetry with two terminal O atoms and two bridging O atoms. (C) 2002 Elsevier Science BN, All rights reserved.