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

This paper is devoted to the third part of the analysis of the very weak absorption spectrum of the O-18(3) isotopologue of ozone recorded by CW-Cavity Ring Down Spectroscopy between 5930 and 6900 cm (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, VI. G. Tyuterev, J. Mol. Spectrosc. (2009), doi: 10.1016/j.jms.2009.02.012 and E. Starikova, M.-R. De Backer-Barilly, A. Barbe, VI. 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 5930-6080 cm (1) regions, respectively. The analysis of the whole investigated region is completed by the present investigation of the 6490-6900 cm (1) upper range. Three sets of interacting states have been treated separately. The first one falls in the 6490-6700 cm (1) region, where 1555 rovibrational transitions were assigned to three A-type bands: 3 nu(2) + 5 nu(3), 5 nu(1) + nu(2) + nu(3) and 2 nu(1) + 3 nu(2) + 3 nu(3) and one B-type band: nu(1) + 3 nu(2) + 4 nu(3). The corresponding line positions were reproduced with an rms deviation of 18.4 x 10 (3) cm (1) by using an effective Hamiltonian (EH) model involving eight vibrational states coupled by resonance interactions. In the highest spectral region -6700-6900 cm (1) 389 and 183 transitions have been assigned to the nu(1) + 2 nu(2) + 5 nu(3) and 4 nu(1) + 3 nu(2) + nu(3) 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 nu(1) + 2 nu(2) + 5 nu(3) band were reproduced with an rms deviation of 7.3 x 10 (3) cm (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 4 nu(1) + 3 nu(2) + nu(3) band (rms = 5.7 x 10 (3) cm (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 5930-6900 cm (1) spectral region were gathered and used for a comparison of the band centres to their calculated values. The agreement achieved for both O-18(3) and O-16(3) (average difference on the order of 1 cm (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 O-18(3) and O-16(3) band intensities is also discussed, opening a field of questions concerning the variation of the dipole moments and resonance intensity borrowing by isotopic substitution. (C) 2009 Elsevier Inc. All rights reserved.