The v 3 and 2v 3 I.R. bandshapes and dipole correlation functions of compressed gaseous N2O; intensity measurements of the 2v 3 band

The I.R. spectrum of the ν₃ band (4·5 µm) of N₂O has been studied for temperatures varying from 219 to 298 K and densities up to 85 kg m^-3. The 2v ₃ band (2·3 µm) has been analysed at room temperature for densities up to 182 kg m^-3; measurements of the integrated intensities as a function of density show no evidence of pressure induced absorption. This band has also been observed in the vicinity of the critical region.

The dipole moment autocorrelation function is used to assess a collisional model derived from the impact approximation and the Gordon M- and J-diffusion models developed classically as well as the semi-classical M-diffusion model. The M- and J-diffusion models reproduce well the experimental correlation function for the ₃ band; the semi-classical M-diffusion model is better than the classical ones for the overtone 2v ₃ and gives a satisfactory account of the correlation functions. For the collisional model considered which implies uncorrelated rotational levels, a discrepancy between theoretical and experimental correlation functions and bandshapes becomes noticeable from about 40 kg m^-3 and increases with density.