Codeposition of thermally generated atomic germanium vapor and nitrous oxide (N 2 O) in Ar onto a substrate at 11 K produced infrared absorption lines in several sets. The most prominent comprises intense lines at 1443.7, 1102.4, and 784.0 cm -1 that become diminished upon irradiation with UV or visible light. These lines are attributed to ν 1 (NO stretching), ν 2 (NN+GeN stretching), and ν 3 (NNO bending+NN stretching) modes of singlet GeNNO. Two additional weak features at 1238.1 and 2859.2 cm -1 are assigned as ν 3 + ν 4 and 2 ν 1 of GeNNO, respectively. Weak doublet features at 1259.3/1255.5 and 1488.9/1486.4 cm -1 are tentatively assigned to ν 2 of triplet GeONN and ν 1 of singlet c yc-Ge- η 2 [NN(O)], respectively. Quantum-chemical calculations on the Ge+ N 2 O system with density-functional theory (B3LYP /aug-cc-pVTZ) predict five stable structures: GeNNO (singlet and triplet), singlet c yc-Ge- η 2 [NN(O)], triplet c yc-Ge- η 2 (NNO), GeONN (singlet and triplet), and singlet GeNON. Vibrational wavenumbers, relative IR intensities, and N 15 -isotopic ratios for observed species are consistent with those computed. Irradiation of singlet GeNNO with λ=248 or 193 nm or λ>525 nm yields GeO.