Abstract
Two radical species were formed when cyanoacetylurea CNCH2CONHCONH2 crystals were irradiated with x ray. One was a π‐electron radical, CNĊHCONHCONH2, and the other a σ‐electron radical, CNCH2CONHCOṄH. The latter was found to have similar hyperfine coupling tensors as H2NCOCH2CONH which was formed in x‐irradiated malonamide, and the former as CNĊHCOOH which was formed in γ‐irradiated cyanoacetic acid.