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The absorption spectrum of the O-18(3) isotopologue of ozone was recorded by cavity-ring-down spectroscopy between 7920 and 7985 cm(-1) with a routine noise equivalent absorption, alpha(min), on the order of a few 10(-11) cm(-1). This permitted to detect and analyze an extremely weak vibrational band assigned as 7 nu(1) + nu(3) following predictions from the ab initio potential energy surface reported in J Chem Phys 2013;139:134307. This is the most excited rovibrational band of the O-18(3) isotopologue detected so far. In total, 259 ro-vibrational transitions were measured and modeled using an effective Hamiltonian model. The vibrational dipole transition moment parameter of the band deduced from the analysis and the fit to 177 experimental line intensities was evaluated as 2.6 x 10(-6) Debye. The absorption coefficient of the recorded pure O-18(3) spectrum was found significantly smaller compared to that of the O-16(3) in the same range. The set of 171 upper state energies experimentally determined cover the range from 92.6% (at J = 1) to 97% (at J = 26) of the first dissociation threshold D-0. The comparison with ab initio predictions for the band origin and nu-dependent rotational constants is discussed. An absorption line list containing 477 transitions is provided as Supplementary material for the 7 nu(1) + nu(3) band. (C) 2021 Elsevier Ltd. All rights reserved.

This work continues the investigation of high resolution infrared spectra of ¹⁷ O and ¹⁸ O enriched ozone isotopomers in the 10 µm spectral range. Spectra are recorded by the Reims Fourier Transform Spectrometer. In a mixture of 18 isotopic species of ozone including ¹⁷ O, ¹⁶ O and ¹⁸ O oxygen atoms, two ν 3 bands are analyzed for the first time: those of ¹⁷ O ¹⁷ O ¹⁸ O and ¹⁷ O ¹⁸ O ¹⁷ O species. The analyses, performed accounting for interactions between the (100)and (001)states, permitted to assign 769 transitions for ¹⁷ O ¹⁸ O ¹⁷ O and 1290 for ¹⁷ O ¹⁷ O ¹⁸ O. The resulting sets of effective Hamiltonian parameters allow reproducing observed transitions within experimental accuracies and calculating synthetic spectra in excellent agreement with the observed ones. We also report here the comparison of main fitted parameters with recent theoretical predictions.

Thirteen bands of the CS symmetry 16O18O18O ozone isotopic species were observed in spectra generated from 16O2/18O2 mixtures recorded between 950 and 3500 cm−1. Experimentally and theoretically this work is similar to the one on the 16O16O18O isotopologue analysis, recently published [Barbe A, et al. J. Quant. Spectrosc. Radiat. Transfer, 2018;218;231–247]. In total 11402 rovibrational transitions (corresponding to 8784 upper state energy levels) were assigned. The line positions are modelled with the root mean squares deviations varying from 0.001 to 0.002 cm−1. The final comparisons show a good agreement between experimental and theoretical band centres and rotational constants predicted from ab initio potential energy surface. Effective dipole transition moment parameters were either fitted or estimated from a comparison between observed and simulated spectra. The line lists built using effective Hamiltonian and transition moment parameters containing 61194 transitions are provided in Supplementary Materials.

Ozone formation and depletion play a key role in various physical and chemical atmospheric processes which remain to be understood in more detail. The modeling of such phenomena based on ozone dynamics calculations requires a detailed knowledge of quantum states, transition probabilities, and ozone potential energy surface (PES) near the dissociation threshold ${D}_{0}$. Knowledge of highly excited rovibrational states with energies approaching ${D}_{0}$ is necessary for a reliable interpretation of satellite measurements of the ozone absorption or emission in the upper atmosphere in nonlocal thermodynamic equilibrium conditions. In addition, these states provide an ideal probe of PESs computed by ab initio methods but their detection by absorption spectroscopy is particularly challenging due to the sharp decrease of the intensity with the energy of the corresponding vibrational combination and overtone bands. In this work, two very high-energy vibrational bands are detected by high sensitivity cavity ring-down spectroscopy providing a noise equivalent absorption ${\ensuremath{\alpha}}_{\mathrm{min}}$ on the order of a few ${10}^{\ensuremath{-}11}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$. The corresponding cold bands, assigned as ${\ensuremath{\nu}}_{1}+6{\ensuremath{\nu}}_{2}+3{\ensuremath{\nu}}_{3}$ and $6{\ensuremath{\nu}}_{1}+{\ensuremath{\nu}}_{2}+{\ensuremath{\nu}}_{3}$ centered at 7969 and $7993\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$, respectively, are about nine orders of magnitude less intense than the well-known ${\ensuremath{\nu}}_{3}$ fundamental band near 10 \textmu{}m. The spectrum analysis allowed for the experimental determination of 240 rovibrational energy levels of the upper vibrational states. The corresponding rotational patterns, located between 93.1% and 96.7% of the dissociation threshold, are the most excited ones measured so far by absorption spectroscopy. The values of the band centers and rotational constants derived from the spectrum analysis provide further confirmation of the absence of an activation barrier on the minimum-energy path towards the dissociation threshold [Tyuterev et al., Phys. Rev. Lett. 113, 143002 (2014)]. The vibrational dynamics is discussed in the context of the radiative transition probabilities and related Einstein coefficients for the observed bands. Another important question in the context of the nuclear dynamics concerns the interaction among the three identical potential wells of the ozone molecule in the ground electronic state, which appears to be due to the Jahn-Teller effect. Recent theoretical results accounting for the three potential wells in a full symmetry approach predicted that vibration states should exhibit deviations from the conventional one-potential-well ab initio calculations, near the dissociation threshold. In the present work, we observe a better agreement of the experimentally determined energy value with the three-wells prediction for the (1,6,3) vibrational state involving a large simultaneous excitation of both bending (${\ensuremath{\upsilon}}_{2}=6$) and asymmetric stretch (${\ensuremath{\upsilon}}_{3}=3$) vibrations pointing towards a nearby well. This could be tentatively interpreted as a manifestation of the three-wells effect.

This article addresses the question of entrepreneurial activity of older people. Using the methods of comparative analysis and benchmarking, as well as the experience of Russian and foreign companies, the authors identify common patterns and national characteristics, as well as the specifics of support and development of entrepreneurship at a mature age. Based on the conducted analysis, the authors give recommendations on the support system for older entrepreneurs, including such measures as the creation of the specific educational courses, corporate mentoring and curatorial programmes as well as the development of special lending systems.

The room temperature absorption spectrum of 13CH4 is recorded by high sensitivity cavity ring down spectroscopy (CRDS) near 1.58 µm. The investigated region (6147–6653 cm−1) corresponds to a spectral region of weak absorption located between the strong bands of the tetradecad and icosad. The sensitivity of the recordings allowed for the measurement of more than 13000 lines for which line centers and line intensities are derived using a multiline fitting program. The obtained list is the first extensive list of 13C enriched methane in the region. It is believed to include a significant number of lines of 13CH3D. In addition, 185 lines were measured at 80 K by direct absorption spectroscopy (DAS) near 6600 cm−1. The line intensity detectivity threshold is on the order of a few 10−29 cm/molecule for the CRDS recordings at 296 K and 10−26 cm/molecule for the DAS recordings at 80 K. From the intensity ratio of the lines in common in the 296 K and 80 K empirical line lists near 6600 cm−1, 438 empirical values of the lower state energy level (Eemp) were derived. An additional set of 200 Eemp values were obtained by combining the present CRDS line intensities to DAS literature data near 6150 cm−1. The comparison to the TheoReTS ab initio line list shows an overall very good agreement for the line intensities. Significant deviations on the order of 0.1 cm−1 are noted for line positions. The obtained experimental data will be valuable to tune ab initio line positions to empirical values in future versions of the theoretical line lists. Finally, a first set of 900 lines belonging to the 5ν4 and ν2 + 4ν4 bands of the icosad are rovibrationally assigned on the basis of an effective Hamiltonian model. The energy values of the involved vibrational sublevels are reported.

The participation of business in partnership initiatives for sustainable development has intensified significantly since the Earth Summit in Rio de Janeiro in 1992. By 2014, there were about 1,000 voluntary commitments and multilateral partnerships in various fields of activity involving partners from the corporate sector , among which the best-known initiatives are “Sustainable Energy for All” (SE4All), “Every Woman, Every Child” (Every Woman Every Child - EWEC), Business Fights Poverty, Partnerships for Small Island Developing States, and others. In our opinion, it seems appropriate to propose the classification of existing partnership models in the interests of achieving the SDGs with the participation of representatives of the corporate sector.

Fifteen bands of the most abundant asymmetric ozone isotopomer 16O16O18O were observed in new spectra generated from various 18O2/16O2 mixtures in the 950–3850 cm−1 range. These bands were fully analyzed, leading to the assignment of a total of 9976 transitions, corresponding to 7030 upper state rovibrational energy levels. The analyses include also six “dark” vibrational states perturbing upper states of the observed bands through anharmonic and Coriolis resonance coupling. The modeling of very congested spectra simultaneously containing lines of six isotopic species resulted to the root mean squares deviations that vary from 0.001 to 0.003 cm−1 in line positions, not exceeding the experimental accuracy. To this end, two different approaches both guided by the ab initio theory were employed. Below 2500 cm−1, all the interacting vibrational states involved in the usual polyad scheme corresponding to the same total stretching excitation were observed. In these cases all symmetry allowed Coriolis and anharmonic coupling terms were initially predicted from ab initio potential energy surface (PES) using the contact transformation method. The major coupling terms were then held fixed to theoretical values during the least-square fits of the observed transitions in order to avoid correlations among adjusted parameters. Above 2500 cm−1, some bands were too weak to be observed. In these cases, the observations did not permit including complete stretching polyads and we used truncated effective models, for which the theory helped to predict initial values of the band centers, their assignments and vibrational dependence of Av, Bv, Cv rotational constants. The final comparison of fifteen experimentally detected and ab initio band centers of 16O16O18O gave the rms deviation of 0.59 cm−1. This drops down to 0.09 cm−1 when using the PES that had been empirically optimized to 16O3 data. The (observed-predicted) rms deviation for Av and Bv is very small - about 0.1%. Average deviations for Cv are somewhat larger ∼0.8% as they are affected by Coriolis resonances. Effective dipole transition moment parameters were either fitted or estimated from a qualitative comparison of observed and simulated spectra involving overlapping contributions of various isotopic species. The line lists built from data reduction models containing about 51,100 transitions are provided in Supplementary Materials.

The paper presents the results of the analysis of experimental FTS infrared vibration-rotation spectra of 16O3 ozone isotopologue recorded in Reims University in the range from 900 to 5600 cm−1, which was used for the current version of the SM http://smpo.univ-reims.fr). The majority of the reported data is related to the accurate determination of line positions. New parameters of effective Hamiltonian (EH) models for three polyads of vibrational states {(001), (100)}, {(011), (110)} and {(002), (101), (030), (200)} obtained from accurate fits of observed spectra in 900 – 2200 cm−1 range, have also been described. Further, at the higher wavenumber range 2700 – 5600 cm−1, various perturbations in the observed spectra due to accidental ro-vibrational resonances and which have been at the root of a lack of accuracy in certain regions of the previously published line lists were identified. We have applied empirical corrections to line positions and to corresponding energy levels in cases where the EH models did not provide the target accuracy of 10−3 cm−1 given of more complex polyad structures, which in turn allowed the use of corrected energy levels to compute improved line positions for the hot bands. In terms of line intensities, we publish here the effective dipole moment parameters and the line lists with empirically-determined absolute intensities for the ν1/ν3 dyad which are consistent with recent ab initio calculations for the strongest bands. For the higher wavenumber range, the empirical corrections are applied for relative intensities of some series of individual transitions in order to improve the simulation of observed spectra. A significant part of the reported data is included in the 2020 release of the HITRAN database.

The spectra of ozone, enriched by 17O oxygen, were recorded and reinvestigated in the 5 μm and 10 μm regions using the Reims Fourier Transform Spectrometer. Here we focus on the analysis of the ν1, ν3 and ν1+ν3 bands of the 16O17O16O isotopologue, which were modeled simultaneously to improve the parameters of the ground state energy level. The analysis of the ν1+ν3 bands of 16O16O17O is also extended. We report here the new system of effective Hamiltonian parameters, give some examples of comparison between observed and simulated spectra, and of the improvement for the ro-vibrational transition data available in spectroscopic databases.

Accurate knowledge of line parameters, and particularly line intensities is of primary importance for satellite, ground based and balloon measurements of the ozone concentration in the atmosphere. Self-consistency in absolute band intensities of ozone in various spectral intervals is necessary to avoid discrepancies in the atmospheric ozone retrieval from different windows. Difficulties in precise experimental characterization of absolute line intensities of this unstable molecule are well known leading to many significant deviations in published intensity values and in spectroscopic compilations. Ab initio intensities computed from the dipole moment functions of our previous works (Tyuterev et al. JCP 2017;146:064304; JCP 2019;150:184303) have permitted achieving a consistency between Stark-effect measurements and various databases in 10 and 5 µm in a good agreement with the most accurate recent experiments. In this paper we extend ab initio corrections to available line lists of ozone band intensities in wider IR range up to the bands with four vibrational quanta. About 40% of intensities were corrected in the 0 - 4122 cm−1 range for thirty cold and hot bands of the main ozone 16O3 isotopologue. Most of them, but not all, were obtained using band specific scaling factors ranging from 0.75 to 1.17 making quite significant changes in the absolute values. The full line lists containing corrected line intensities in the spectral intervals considered in the paper are provided in the Supplementary material for this work. The resulting line list is now available on the web site of the “Spectroscopy and Molecular Properties of Ozone” (SM http://smpo.univ-reims.fr ). A large part of this line list including the ab initio correction reported in this work will be used in the future HITRAN20 update.

This work continues our investigation on the high resolution infrared 13C-enriched spectrum of methane recorded on a Bruker IFS-125HR Fourier transform spectrometer at 80 K in the 4970–6200 cm−1 range. In this paper we report the results of assignment and modelling of the line positions and intensities of 13CH4 in the range between 5471 and 5852 cm−1, corresponding to the middle part of Tetradecad. The analysis was performed using a non-empirical effective Hamiltonian (EH) derived from the ab initio potential energy surface (PES) by high-order Contact Transformations (CT). The EH parameters were empirically optimized during the treatment of experimental data. In total, 3297 lines belonging to nine cold bands of the Tetradecad of 13CH4 were assigned in the 5471–5852 cm−1 range up to Jmax = 11. The 3297 lines included correspond to 91% of the total line number in the region. Among them, 3251 line positions were fitted with an rms deviation of 1.33×10−3 cm−1. Measured line intensities for 1624 transitions were modeled using the effective dipole transition moments approach with an rms deviation of about 9%. Finally, the observed transitions were incorporated to fit simultaneously the 13CH4 Hamiltonian parameters for the {Ground state/Dyad/Pentad/Octad/Tetradecad} system and the dipole moment parameters for the {Ground state - Tetradecad} system.

In a mixture of 18 isotopic species of ozone including 17O, 16O and 18O oxygen atoms, four ν1+ν3 bands of 17O3, 17O17O18O, 16O17O17O, 17O16O17O in the 5 µm range are analyzed for the first time. The analyses, accounting for interactions between (101) with (002) and (200) states permitted to assign respectively 747 transitions for 17O17O18O, 705 transitions for 17O16O17O, 889 transitions for 16O17O17O and 1404 transitions for 17O3. The results of fits of effective Hamiltonian and transition moment parameters permit reproducing observed transitions within experimental accuracy. They allow to calculate synthetic spectra in excellent agreement with the observed ones. The band centers and rotational constants derived from experimental spectra are in good agreement with recent theoretical predictions from potential energy surfaces.

International audience; Reliable ozone spectral data consistent over several spectral ranges are a challenge for both experiment and theory. We present ab initio calculations for strong lines that lead to consistent results from the microwave to mid-infrared regions. The results agree well with established microwave line lists and our new measurements in the fundamental and first overtone regions of ozone at 5 and 10 μm. The calculations and their agreement to within 1% with measurements provide an important step toward consistent and accurate spectroscopic ozone data. The results imply that actual databases need to be corrected by about 3% in the corresponding mid-infrared spectral intervals. Appropriate recommendations for the consistency of strong line intensities of the ozone molecule in microwave, 10 and 5 μm ranges, in HITRAN (HIgh-resolution TRANsmittance and molecular apbsorption) and GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques) databases are suggested.I. INTRODUCTION

The absorption spectrum of the 13CH4 methane isotopologue has been recently recorded by Differential Absorption Spectroscopy (DAS) at 80 K in the 5853–6201 cm−1 spectral range. An empirical list of 3717 lines was constructed for this spectral range corresponding to the upper part of the Tetradecad dominated by the 2ν3 band near 5987 cm−1. In this work, we present rovibrational analyses of these spectra obtained via two theoretical approaches. Assignments of strong and medium lines were achieved with variational calculations using ab initio potential energy (PES) and dipole moment surfaces. For further analysis a non-empirical effective Hamiltonian (EH) of the methane polyads constructed by high-order Contact Transformations (CT) from an ab initio PES was employed. Initially predicted values of EH parameters were empirically optimized using 2898 assigned line positions fitted with an rms deviation of 5×10−3 cm−1. More than 1860 measured line intensities were modeled using the effective dipole transition moments approach with the rms deviation of about 10%. These new data were used for the simultaneous fit of the 13CH4 Hamiltonian parameters of the {Ground state/Dyad/Pentad/Octad/Tetradecad} system and the dipole moment parameters of the {Ground state-Tetradecad} system. Overall, 10 vibrational states and 28 vibration sublevels of the 13CH4 Tetradecad are determined. The comparison of their energy values with corresponding theoretical calculations is discussed.

A 13C-enriched spectrum of methane (13CH4) was recorded at Doppler-limited resolution (0.0044 cm−1) at 80 K covering the entire Tetradecad region in the 4970–6200 cm−1. In this paper we present the spectral analysis of the lower part of the 13CH4 Tetradecad in the 4970–5470 cm−1 region. Starting with a non-empirical effective Hamiltonian derived by high-order Contact Transformations (CT) from the ab initio potential energy surface (PES), the effective Hamiltonian parameters have been determined for this region by extending the previous DAS (Differential Absorption Spectroscopy) spectral analysis for the upper part of the Tetradecad in the 5853–6200 cm−1 region. In total, 1387 rovibrational transitions were assigned belonging to five cold bands of the Tetradecad up to Jmax = 11. Their positions were fitted with an rms deviation of 1.6 × 10−3 cm−1. Measured line intensities for 737 transitions were modeled using the effective dipole transition moments approach with an rms deviation of about 10%. Finally, the observed transitions were incorporated to fit simultaneously the 13CH4 Hamiltonian parameters for the {Ground state / Dyad / Pentad / Octad / Tetradecad} system and the dipole moment parameters for the {Ground state - Tetradecad} system.

Three very weak bands of the 18O16O18O isotopologue of ozone have been detected by high sensitivity CW-Cavity Ring Down Spectroscopy between 6340 and 6800 cm−1. They are vibrationally assigned as 2ν1+5ν3, ν1+4ν2+3ν3 and 3ν2+5ν3 and correspond to the highest frequency bands of this isotopologue detected so far. A total of 464, 318 and 194 transitions were rovibrationally assigned, respectively. The good agreement with theoretical values achieved for the derived band centres and rotational constants confirms the accuracy of the potential energy surface recently obtained via extensive ab initio calculations. A set of line intensities was measured and fitted to derive the first transition moment parameter of the three bands. The determined sets of effective Hamiltonian parameter and transition moment operators, as well as the experimental energy levels, were used to generate a complete list of 1526 transitions, provided as Supplementary materials . The calculated line-list allows generating a synthetic spectrum which reproduces satisfactorily the experimental spectrum.

This work continues the systematic investigation of high resolution infrared spectra of 18O enriched ozone isotopologues in the 4500–6300 cm−1 spectral range. So far, the 16O18O16O and 18O16O18O spectra have been recorded and analysed using Fourier Transform Spectrometer (FTS) below 5000 cm−1 and using high sensitivity Cavity Ring-Down Spectroscopy above 6000 cm−1. In order to fill the gap between 5000 and 6000 cm−1, new infrared spectra were recorded with the Reims FTS. The analyses of the 2ν1+ν2+3ν3 band of 16O18O16O and of the 5ν3, ν1+2ν2+3ν3 and ν1+5ν3 bands of 18O16O18O are reported. New ν1+2ν2+3ν3 and ν1+5ν3 bands of 18O3 were also observed and analysed. Observed line positions were fitted using effective Hamiltonian models accounting for the dark state perturbations. The derived band centres and rotational constants are in a good agreement with new theoretical calculations from the molecular potential function.

The 13CH4 absorption spectrum has been recorded at 296 K and 80 K in the Icosad range between 6600 and 7700 cm−1. The achieved noise equivalent absorption of the spectra recorded by differential absorption spectroscopy (DAS) is about αmin ≈ 1.5 × 10−7 cm−1. Two empirical line lists were constructed including 17,792 and 24,139 lines at 80 K and 296 K, respectively. For comparison, the HITRAN database provides only 1040 13CH4 lines in the region determined from methane spectra with natural isotopic abundance. Empirical values of the lower state energy level, Eemp, were systematically derived from the intensity ratios of the lines measured at 80 K and 296 K. Overall 10,792 Eemp values were determined providing accurate temperature dependence for most of the 13CH4 absorption in the region (93% and 82% at 80 K and 296 K, respectively). The quality of the derived empirical values of the lower state rotational quantum number, Jemp, is illustrated by their clear propensity to be close to an integer. A good agreement is achieved between our small Jemp values, with previous accurate determinations obtained by applying the 2T method to jet and 80 K spectra. The line lists at 296 K and 80 K which are provided as Supplementary material will be used for future rovibrational assignments based on accurate variational calculations.

The present contribution is devoted to the analysis of three extremely weak A-type bands of 16O3 recorded near 7686, 7739 and 7860 cm−1 i.e. only a few % below the dissociation limit, D0, at about 8560 cm−1. They correspond to the most excited vibration–rotation states of ozone observed so far via high-resolution absorption spectroscopy. They were detected by high sensitivity CW-cavity ring down spectroscopy with a typical noise equivalent absorption, αmin, on the order of 2×10−10 cm−1 and modelled using the effective operator approach. The derived band centres and rotational constants show a very good agreement with recent theoretical predictions based on a new ab initio potential energy surface.

The absorption spectrum of the 18 O 3 isotopologue of ozone is recorded by CW-Cavity Ring Down Spectroscopy between 7400 and 7920 cm −1 . The typical noise equivalent absorption of the recordings is α min ≈1×10 −10 cm −1 allowing for the detection of extremely weak vibrational bands located only a few % below the dissociation limit. The absorption spectrum also includes the weak 3 A 2 (000)–X(110) hot vibronic band at 7877.53 cm −1 affected by predissociation broadening. Overall, about 1000 lines were rovibrationnally assigned to six vibrational bands. Their line positions were modelled using effective Hamiltonian models covering three vibrational interacting systems and involving several “dark” states perturbing observed transitions. Line positions could be reproduced with rms deviations on the order of 0.01 cm −1 . The dipole transition moment parameters of the six bands were determined from the retrieved line intensities. The obtained set of effective parameters and the experimentally determined energy levels were used to generate a list of 1461 transitions provided as Supplementary materials .

The far-infrared emission spectra of deuterated water vapour were measured at different temperatures (1370, 1520, and 1950 K) in the range 320–860 cm−1 at a resolution of 0.0055 cm−1. The measurements were performed in an alumina cell with an effective length of hot gas of about 50 cm. More than 1150 new measured lines for the D216O molecule corresponding to transitions between highly excited rotational levels of the (0 0 0) and (0 1 0) vibrational states are reported. These new lines correspond to rotational states with higher values of the rotational quantum numbers compared to previously published determinations: Jmax=26 and K a (max) =26 for the (0 0 0) ← (0 0 0) band, Jmax=25 and K a (max) =25 for the (0 1 0) ← (0 1 0) band, and Jmax=26 and K a (max) =18 for the (0 1 0) ← (0 0 0) band. The estimated accuracy of the measured line positions is 0.0005 cm−1. To our knowledge no experimentally measured rotational transitions for D216O within an excited vibrational state have been available in the literature so far. An extended set of experimental rotational energy levels for (0 0 0) and (0 1 0) vibration states including all previously available data has been determined. For the data reduction we used the generating function model. The root mean square (RMS) deviation between observed and calculated values is 0.0012 cm−1 for 692 rotational levels of the (0 0 0) state and 0.0010 cm−1 for 639 rotational levels of the (0 1 0) vibrational state. A comparison of the observed energy levels with the best available values from the literature and with the global predictions from molecular electronic potential energy surface [J. Chem. Phys. 106 (1997) 4618] for the (0 0 0) and (0 1 0) states is discussed.

Since the discovery of anomalies in ozone isotope enrichment, several fundamental issues in the dynamics linked to the shape of the potential energy surface in the transition state region have been raised. The role of the reeflike structure on the minimum energy path is an intricate question previously discussed in the context of chemical experiments. In this Letter, we bring strong arguments in favor of the absence of a submerged barrier from ultrasensitive laser spectroscopy experiments combined with accurate predictions of highly excited vibrations up to nearly 95% of the dissociation threshold.