JOURNAL OF MOLECULAR SPECTROSCOPY 187, 70–74 (1998) ARTICLE NO. MS977483 First Study of the £ 2 Å 3 Dyad {(130), (031)} of Ozone through the Analysis of Hot Bands in the 2300–2600 cm 01 Region A. Barbe,* S. Mikhailenko,² J. J. Plateaux,* and Vl. G. Tyuterev* *Groupe de Spectrome ´trie Mole ´culaire et Atmosphe ´rique, UPRESA CNRS Q 6089, UFR Sciences, BP 1039, 51687 Reims Cedex 2, France; and ² Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, 1 Akademicheskii Av., 634055, Tomsk, Russia Received July 24, 1997; in revised form November 3, 1997 Hot bands n 1 / 3n 2 0 n 2 and 3n 2 / n 3 0 n 2 of 16 O 3 in the region 2300–2600 cm 01 and the cold band 3n 2 / n 3 in the region 3050–3110 cm 01 , corresponding to the £ 2 Å 3 dyad {(130), (031)}, have been observed for the first time, using the Fourier Transform Spectrometer (FTS) at Reims and the usual experimental setup providing a large product pressure 1 path length, p 1 l . Three hundred sixty-five rovibration energy levels of the upper states were obtained with J and K a up to 46 and 9, respectively. The fit of these data gives a r.m.s. deviation of 1.93 1 10 03 cm 01 . The £ 2 dependence of the rotational parameters A , B , and C for the (1£ 2 0) and (0£ 2 1) states is discussed.  1998 Academic Press INTRODUCTION calibration ( 9, 19 ), the absolute accuracy is estimated to be 1.5 1 10 03 cm 01 . Continuing the systematic study of weak bands of ozone ( 1–14 ) we reported new bands in the range 3000–6000 ANALYSIS cm 01 . Recently, we have observed for the first time transi- tions involving the £ 2 Å 3 state: the n 1 / 3n 2 / n 3 band 1. Assignment ( 15 ). This analysis was very interesting with regard to the We recently reported ( 15 ) the analysis of the state (131) behavior of rotational constants with respect to £ 2 quantum through the observation of n 1 / 3n 2 / n 3 and n 1 / 3n 2 / number: we observed in ozone, due to the proximity v 1 / n 3 0 n 2 bands. This allowed us to derive a nearly linear v 3 É 3v 2 , many Coriolis perturbations involving £ 2 Å 3, 4, or variation of rotational constants A , B , and C and the centrifu- 5. These bands, which are too weak to be observed, usually gal distortion constant D K with respect to £ 2 quantum num- correspond to upper state levels that appear as a ‘‘dark state’’ ber. On the other hand, with our experimental S/N ratio through perturbations. Then good knowledge of the rota- ( 17 ) on the order of 700, we were in principle able to observe tional constants allows us to derive their band centers and two hot bands 3n 2 / n 3 0 n 2 and n 1 / 3n 2 0 n 2 , taking then to derive information important for the potential func- into account the transition moment of 2n 2 / n 1 and 2n 2 / tion determination. n 3 ( 20 ) with the  3 and Boltzmann factors: these led to In this study, we observe for the first time the states ( 130 ) intensities of about 9% of those of the corresponding cold and (031) through the analysis of hot bands in the region band. Also, the new refined vibrational extrapolations ( 21 ) 2300–2600 cm 01 . allowed us to determine the band centers with an accuracy better than 1 cm 01 . Then we performed a first calculation EXPERIMENT of both states, thanks to these extrapolations. After a few attempts and using ground state energy differences, we were The spectra were recorded with the FTS at Reims ( 16 ), finally able to assign transitions of both bands, with J on where new improvements concerned with S / N ratio and zero the order of 10 and K a Å 0, 1, and 2. With the usual procedure transmittance have been obtained ( 17 ) . Ozone was prepared of successive fits and predictions we finally assigned all the by the usual procedure explained in various references ( 18 ). transitions of the bands, in the range of J and K a given in In this study we used a White cell of 3216 cm and a mixture Table 1. of O 3 and O 2 , the partial pressure of O 3 was 21.10 Torr, and the total pressure was 44.50 Torr. The beamsplitter was 2. Rovibrational Energy Level Calculations CaF 2 , and InSb was the detector. The S/N ratio is on the order of 700, as observed in Fig. 1. The apodized resolution To correctly reproduce the rovibrational energy levels, we used two different models. The first is two single state was adjusted to the Lorentzian width at these pressures. As the lines for these hot bands are very weak, the retrieved Hamiltonians ( see 6 ) separately for the (031) and (130) states. The corresponding parameter values are given in Ta- accuracy for wavenumbers is not much better than 0.8 1 10 03 cm 01 . Adding the small pressure shift for the reference ble 2 with their standard errors. Since the maximum values 70 0022-2852/98 $25.00 Copyright  1998 by Academic Press All rights of reproduction in any form reserved. AID JMS 7483 / 6t26$$$381 01-30-98 15:21:04 mspal