CW-Cavity Ring Down Spectroscopy of 18O3. Part 3: Analysis of the 6490–6900cm−1 region and overview comparison with the 16O3 main isotopologue (original) (raw)

2009, Journal of Molecular Spectroscopy

This paper is devoted to the third part of the analysis of the very weak absorption spectrum of the 18O3 isotopologue of ozone recorded by CW-Cavity Ring Down Spectroscopy between 5930 and 6900cm−1. In the two first parts [A. Campargue, A. Liu, S. Kassi, D. Romanini, M.-R. De Backer-Barilly, A. Barbe, E. Starikova, S.A. Tashkun, Vl.G. Tyuterev, J. Mol. Spectrosc. (2009), doi: 10.1016/j.jms.2009.02.012 and E. Starikova, M.-R. De Backer-Barilly, A. Barbe, Vl.G. Tyuterev, A. Campargue, A.W.Liu, S. Kassi, J. Mol. Spectrosc. (2009) doi: 10.1016/j.jms.2009.03.013], the effective operators approach was used to model the spectrum in the 6200–6400 and 5930–6080cm−1 regions, respectively. The analysis of the whole investigated region is completed by the present investigation of the 6490–6900cm−1 upper range. Three sets of interacting states have been treated separately. The first one falls in the 6490–6700cm−1 region, where 1555 rovibrational transitions were assigned to three A-type bands: 3ν2+5ν3, 5ν1+ν2+ν3 and 2ν1+3ν2+3ν3 and one B-type band: ν1+3ν2+4ν3. The corresponding line positions were reproduced with an rms deviation of 18.4×10−3cm−1 by using an effective Hamiltonian (EH) model involving eight vibrational states coupled by resonance interactions. In the highest spectral region – 6700–6900cm−1 – 389 and 183 transitions have been assigned to the ν1+2ν2+5ν3 and 4ν1+3ν2+ν3 A-type bands, respectively. These very weak bands correspond to the most excited upper vibrational states observed so far in ozone. The line positions of the ν1+2ν2+5ν3 band were reproduced with an rms deviation of 7.3×10−3cm−1 by using an EH involving the {(054), (026), (125)} interacting states. The coupling of the (431) upper state with the (502) dark state was needed to account for the observed line positions of the 4ν1+3ν2+ν3 band (rms=5.7×10−3cm−1).The dipole transition moment parameters were determined for the different observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a complete line list provided as Supplementary Materials.The results of the analyses of the whole 5930–6900cm−1 spectral region were gathered and used for a comparison of the band centres to their calculated values. The agreement achieved for both 18O3 and 16O3 (average difference on the order of 1cm−1) indicates that the used potential energy surface provides accurate predictions up to a vibrational excitation approaching 80% of the dissociation energy. The comparison of the 18O3 and 16O3 band intensities is also discussed, opening a field of questions concerning the variation of the dipole moments and resonance intensity borrowing by isotopic substitution.