10min:

J. ORPHAL, Institute of Environmental Physics, University of Bremen, P. O. Box 330440, 28334 Bremen, Germany; M. MORILLON-CHAPEY, LPMA,CNRS and University of Paris-Sud, Bat. 350, 91405 Orsay Cedex, France; S. KLEE, G. CH. MELLAU AND M. WINNEWISSER, Institute of Physical Chemistry, University of Giessen, H.-Buff-Ring 58, 35392 Giessen, Germany.

ClNO₂ is a molecule of potential stratospheric and tropospheric importance, formed by heterogeneous reactions on polar stratospheric clouds and sea-salt particles. In 1994, high-resolution infrared spectra of ClNO₂ were measured and analyzed in the 500--2500 cm^-1 range. However, up to now, no high-resolution absorption spectra of the ₃ and ₅ fundamental bands of ClNO₂ in the far-infrared region were reported, except for microwave observation of a few transitions in the excited vibrational states.

In the present study, absorption spectra in 300--500 cm^-1 range were recorded at resolutions of up to 0.0017 cm^-1, using the Bruker IFS-120HR FTS at University of Giessen. Using these spectra, nearly 2000 transitions of the a -type ₃ band around 370 cm^-1 were assigned. The b -type ₅ band around 411 cm^-1 is too weak to be observed, in agreement with ab-initio predictions. However, the (₂-₃) a -type difference band was observed and could be used to confirm rotational constants of both vibrational states.