Rotation-vibration spectrum of hydrazoic acid in the near infra-red and in the visible

Second and third overtones of N—H stretching vibration in HN3 have been investigated at higher resolving power and pathlength than previously, and the fourth overtone photographed for the first time. The rotational analysis of 3ν1, where more than 500 lines were measured, gives accurate values of the rotational constants of both ground and upper states. A local perturbation was found in levels with K′= 2 and 4. The rotational analysis of 4ν1, where lines are broader than in 3ν1, indicates that the dependence of A from vibrational quantum number v1, is not linear. Owing to the large linewidth (∼0.35 cm–1) only the analysis of the K-structure is possible for 5ν1. The diffuseness in 4ν1 and 5ν1 is discussed in terms of line broadening by case II predissociation.