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A. Barbe, M.R. De Backer-Barilly, Vl.G. Tyuterev, D. Romanini 1 , S.Kassi 1 , A. Campargue 1

Analysis of high resolution infrared CW-CRDS spectra of ozone in the 6000-6750 cm -1 spectral region. A. Barbe, M.R. De Backer-Barilly, Vl.G. Tyuterev, D. Romanini 1 , S.Kassi 1 , A. Campargue 1. Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 6089

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A. Barbe, M.R. De Backer-Barilly, Vl.G. Tyuterev, D. Romanini 1 , S.Kassi 1 , A. Campargue 1

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  1. Analysis of high resolution infrared CW-CRDS spectra of ozone in the 6000-6750 cm-1 spectral region A. Barbe, M.R. De Backer-Barilly, Vl.G. Tyuterev, D. Romanini1, S.Kassi1 , A. Campargue1 Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 6089 Université de Reims Champagne – Ardenne France 1 Laboratoire de Spectrométrie Physique, UMR CNRS 5588, Université Joseph Fourier, Saint Martin d’Hères, France

  2. threshold Laser OFF -50 0 50 100 The compact fibered CW-CRDS spectrometer (Grenoble)1480-1687 nm (5800-7000 cm-1)Typical sensitivity 310-10 cm-1 6nm/diode 40 diodes Laser diode Lambdameter n=f(T,I) Optical isolator Coupler AO Modulator laser ON Photodiode

  3. Illustration of the achieved sensitivity: The example of the a1Δg (0)−X3Sg−(1) of O2 k=8×10-31cm/molec Chem. Phys. Lett. 409 (2005) 281–287

  4. Intensity calculations

  5. Region ( 233-000 ) 6720 cm-1 Observed absorption coefficient (10-6 cm-1)

  6. E/hc (cm-1) Ka = 11 Ka = 3 (412) 6800 Ka = 9, 10 Ka = 4,5,6 Ka = 0,1,2 (242) Ka = 5 Ka = 6,7,8 (520) Ka = 0,1,2 (171) Ka = 5 Ka = 5,6,7 (233) Ka = 10, 11 Ka = 7,8,9 Ka = 12 6700 (313) (350) Ka = 6 6600

  7. % on (520) in (233)

  8. % on (520) in (242)

  9. Spectroscopic parameters (cm-1) Coupling parameters

  10. Statistics for rovibrational transition calculation 7.5

  11. Transition moment operator parameters (Debye)

  12. Statistics for line intensities

  13. Final comparison between Observed and Calculated spectrum Observed Calculated

  14. 360 145 371 144 143 142 141 Observed spectrum Calculated spectrum CO2 H2O Comparison between Obs. and Calc. spectrum in the P branch of 21+32+33 (J’= 14)

  15. Global survey of the 6000 – 6200 cm-1 spectral range 7 different diodes : without impurities : CO2, H2O, CO 5n1+n2 3n2+4n3 2n1+2n2+3n3# n1+2n2+4n3 2n1+3n2+3n3-n2 n1+5n3#

  16. Observing and assigning B type bands (ΔKa= ± 1) in this high level range represents an challenge. With previous work done with the F.T.S, the highest observed bands were 2n1+2n3( 4141 cm-1) and 2n1+n2+2n3 (4783 cm-1). In general , FOR OZONE, this type of band is much more difficult to assign than A type bands, were strong compressed R branch appear, for several reasons: They are much weaker than A type bands at a given energy level range. They extend over a much larger spectral range, and , as a consequence, are never totally observed , being overlapped by stronger A type bands, and often partly hidden by impurities, like H2O,CO2,CO… The general shapes of theses bands are difficult to reproduce in a first attempt, as 6 type of transitions may be observed, and the introduction of unknown additional transition moment parameters is obligatory to reproduce line intensity observations.( as example μ 5 terms must be introduce to “ reduce” Q branches which are not visible in our spectra ).

  17. Calculated spectra of 1+22+43 in 3 cases (normalisation on observed lines in the 6155 cm-1 region) All  of A and B bands All  of B band; A =0 Only 1 for B band ( 5=0):

  18. Observed and calculated spectrum of the n1 + 2n2 +4n3 band in the 6156 – 6157 cm-1 range Calculated 261 280 252 291 312 241 221 201 257 226 301 232 212 192 266 235 Absorption Coefficient (a.u.) Observed * CO2 * * Wavenumber (cm-1)

  19. 310-28 cm-1 molecule cm-2 Observed spectrum Calculated (331)-(000) Calculated (124)-(000) CO2 (331-000) the weakest band observed so far

  20. Assigned transitions in the range 6000—6900cm-1

  21. Vl.G. Tyuterev, H. Seghir, A. Barbe, S.A. Tashkun, « Ozone molecule : high energy resonances, consistency of variational and perturbative calculations and complete vibration assignments up to dissociation », HRMS, Praha 2006

  22. Conclusion This work , thanks to the high sensitivity of the experimental set-up (CW-CRDS) allows to observe many weak rovibrational transitions of ozone. All the « relatively strong or of medium intensity « are rotationally undoubtedly assigned. It confirms previous work done with FTS, that is to say, that above 3300 cm-1,the simplified scheme of ozone, including poylads corresponding to the same value of v2, with Darling-Dennison resonances between v1,v2,v3 and v1±2,v2,v3Ŧ 2 states and coriolis resonances between v1,v2,v3and v1 Ŧ1,v2,v3 ±1 states is no more valid : large vibrational couplings arise between all states in a neighborhood, even with large value of v2. As a result, predictions of the strengths of interactions between various partners become a real challenge, as the number of possibly interacting states become obviously larger and larger as far as energy is increasing. Remember that highest observations are near 7000 cm-1, the dissociation limit being near 8600 cm-1. Prediction of rotational constants also is difficult. Nevertheless, we have been able, in two spectral regions, to complete the works, that is to say find suitable models, for positions and intensities which reproduce correctly ( near the experimental accuracy) the observed spectra. Consequently, we give for these works not only hamiltonian parameters and transition moment parameters, but also energy levels, corresponding to observed transitions. It has also been possible to reproduce B type bands, despite the difficulties mentioned during this talk. A s final conclusion, we will continue to advance theoretically and experimentally, simultaneously, to have a final good understanding of the dipole and potential function of ozone

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