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Abstract
Deviations of experimental millimetre-absorption line shapes from the usual Voigt profile are evidenced for two room-temperature rotational transitions J = 20 ← 19 (502 GHz) and J = 24 ← 23 (602 GHz) of nitrous oxide perturbed by nitrogen and oxygen. These deviations are shown to be due to collisional narrowing processes encompassed by more sophisticated speed-dependent Voigt or Galatry models. The deduced collision-regime line broadening coefficients are compared to their theoretical estimations by a semi-classical formalism. Even with a rough intermolecular potential composed of electrostatic and pair atom–atom interactions, the theoretical linewidths compare favourably with experimental results for both millimetre and infrared absorption.
Acknowledgements
The authors acknowledge with gratitude the financial support from the Programme National de Chimie Atmosphérique from CNRS. The Centre d’Etudes et Recherches Lasers et Applications (CERLA) is supported by the Ministère chargé de la Recherche, the Région Nord-Pas de Calais and the Fonds Européen de Développement Economique des Régions. E.A. thanks the CNRS and the Université de Lille-1 for financial support.