New FTIR CO2 high resolution spectra are recorded in argon and nitrogen mat
rices at 11 K at high dilution. Their evolution with CO2 diffusion at highe
r temperature is also traced. New observations are discussed in regard to p
revious works. Even at high dilution (1/10 000), the temperature increase c
auses appearance of several bands both in argon and nitrogen. Identificatio
n of carbon dioxide dimer absorptions is tentatively proposed, (C) 2000 Els
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