Collisional effects on spectral line-shapes

The growing concern of mankind for the understanding and preserving of its environment has stimulated great interest for the study of planetary atmospheres and, first of all, for that of the Earth. Onboard spectrometers now provide more and more precise information on the transmission and emission of radiation by these atmospheres. Its treatment by ‘retrieval’ technics, in order to extract vertical profiles (pressure, temperature, volume mixing ratios) requires precise modeling of infrared absorption spectra. Within this framework, accounting for the influence of pressure on the absorption shape is crucial. These effects of inter-molecular collisions between the optically active species and the ‘perturbers’ are complex and of various types depending mostly on the density of perturbers. The present paper attempts to review and illustrate, through a few examples, the state of the art in this field. This is to be related with the increasing quality of laboratory or onboard instruments (frequency difference laser, Fourier transform, diode laser spectrometers,…) which nowadays provide data of precision far above than what could be achieved ten years ago. To cite this article: C. Boulet, C. R. Physique 5 (2004).