Fourier Transform Infrared (FTIR) spectra of the covalent dinitrogen pentoxide molecule isolated in a solid argon matrix at 10 K are reported. The measured frequencies in the 200-4000 cm(-1) region are in close agreement with gas phase values previously reported. An accurate and sophisticated ab initio study showed that the stable equilibrium structure, C-2 symmetry, was in agreement with the structure previously determined by electron diffraction data.