Raman spectrum of U₄O₉: a new interpretation of damage lines in UO₂

Characterisation of uranium oxides in different conditions is a challenge both in nuclear and environment sciences. We focus here on U 4 O 9 , which is a superstructure of UO 2 . Homogeneous U 4 O 9 powder was fabricated and characterised by Raman spectroscopy. The Raman spectrum of a pure‐phase U 4 O 9 is, for the first time, completely described and interpreted. U 4 O 9 Raman spectrum derives from the well characterised one of UO 2 . Besides reminiscent modes of UO 2 , a band at 630 cm ‐1 , which has a specific response to polarised light, was interpreted as characteristic of clusters of interstitial oxygen atoms. These experimental data will help to rationalise the interpretation of UO 2 damaged samples.