Spectra and structure of nitrous oxide dimers and clusters

Supersonic expansions of nitrous oxide seeded in argon were studied by single pass FTIR absorption at right angles with the jet axis. In very dilute mixtures, 0.2% N2O, dimer bands at 1282.4 and 2228.0 cm−1 were observed corresponding to the ν1 and ν3 stretches of the monomer. Cluster bands (due to clusters of undetermined size) were readily observed in 20%–100% N2O mixtures at 1165.1, 1295.2, 2245.6, 2467.4, 2578.3, 2811.7, and 3505.8 cm−1. All bands are shifted from the corresponding monomer bands more than in the crystal and in the same direction. Changing the dilution from 10% to 20% shifted all cluster bands 1–2 cm−1 towards low frequencies but still far away from the crystal frequencies. This is interpreted as being due to cluster melting. No increase in bandwidth is associated with the shifts, indicating that, if present at all, the coexistence region described by Berry and co-workers is rather limited in N2O clusters.