by high resolution Fourier transform spectrometry

Ab s o rption of ra d i ation of ozone initiates import a n tchemical transformation in the troposphere, stratos-p h e re and mesosphere although a “ m i n o r ” c o n-stituent. So ex t e n s ive effo rts we re undert a ken these last decades [1,2] to study structure, spectroscopy and excited states, all more or less related to the photochemistry of this molecule. We are particularly interested in the lowest lying excited electronic states that determine absorption in the Near Infra-Red up to visible region. Some of them (metastable) could be sufficiently long-lived to constitute a potentially impor-tant atmospheric reservoir of “hidden ” energetic ozone that may play a significant role in ozone recombination kinetics. They also could be responsible for a number of anomalies in O − O2 photochemistry including kinetics as well as iso-topic enrichment [3]. So contra ri ly to the UV region (Huggins and Hart l ey bands) for which absorption from the ground state is easily detected in the atmosphere (σa about 10−21 − 10−20 cm2/mol-ecule) and is of major importance for the study and moni-toring of the atmospheric ozone layer, in the Near Infra-Red the ab s o rption cross-sections are ve ry weak (σa about 10−23 cm2/molecule) according to the metastable character of Among the five lowest lying excited electronic states of ozone, the triplet 3A2 has been identi-fied and characterised by high resolution Fourier transform absorption spectrometry in the 10000 cm−1 region. This state is responsible of the Wulf transition and has two bound vibrational levels. The analysis of the rotational structure of one band of the 3A2 ← X ~ 1A1 transition allows to deter-mine: spectroscopic constants, geometry and lifetime of ozone in the (0,0,0) level of the 3A2 state, absorption cross-sections in the 9500 − 11500 cm−1 range. Preliminary results are also given concerning the close 3B2 state. Article available a