Ozone Spectra Research Articles

The ν1 + 3 ν2 + 3 ν3 and 4 ν1 + ν2 + ν3 bands of ozone by CW-cavity ring down spectroscopy between 5900 and 5960 cm −1

The absorption spectrum of ozone, 16O 3, has been recorded in the 5903–5960 cm −1 region by high sensitivity CW-cavity ring down spectroscopy ( α min ∼ 5 × 10 −10 cm −1). The ν 1 + 3 ν 2 + 3 ν 3 and 4 ν 1 + ν 2 + ν 3 A-type bands centred at 5919.15 and 5947.07 cm −1 were newly observed. A set of 173 and 168 energy levels could be experimentally determined for the (1 3 3) and (4 1 1) states, respectively. Except for a few K a = 5 levels of the (4 1 1) state, the rotational structure of the two states was found mostly unperturbed. The spectroscopic parameters were determined from a fit of the corresponding line positions by considering the (1 3 3) and (4 1 1) states as isolated. The determined effective Hamiltonian and transition moment operators were used to generate a list of 785 transitions given as Supplementary Material.

CW-Cavity Ring Down Spectroscopy of the ozone molecule in the 5980–6220 cm −1 region

The absorption spectrum of ozone, 16O 3, has been recorded in the 5980–6220 cm −1 region by high sensitivity CW-Cavity Ring Down Spectroscopy ( α min ∼ 3 × 10 −10 cm −1). This study extends a first investigation with the same experimental set-up limited to the 6030–6090 cm −1 spectral region [M.-R. De Backer-Barilly, A. Barbe, Vl.G. Tyuterev, D. Romanini, B. Moeskops, A. Campargue, J. Mol. Struct. 780–781 (2006) 225–233] where the analysis of two A-type bands was reported, using FTS spectra for complementary information. The spectral extension of the recordings allows not only to enlarge considerably the observed transitions of these two bands, but more importantly, to assign four new bands: the 3 ν 2 + 4 ν 3,5 ν 1 + ν 2 and ν 1 + 2 ν 2 + 4 ν 3 B-type bands which were considered as dark in our previous report and the 3 ν 1 + 3 ν 2 + ν 3 A-type band. The high mixing of the observed states approaching the dissociation limit, leads to the breakdown of the polyad structure and ambiguities in the vibrational labelling which are discussed. Finally, 1789 transitions were assigned, and a suitable Hamiltonian model allows reproducing correctly the observations for five of the six observed bands. The list of 1004 experimentally determined energy levels is provided. The determined effective Hamiltonian and transition moment operators were used to generate a list of 5338 transitions given as Supplementary Material. It is interesting to note that the d 5 parameter of the effective transition moment is of great importance to account for the observed intensities of the B-type bands.

CW-cavity ring down spectroscopy of the ozone molecule in the 6625–6830 cm −1 region

The absorption spectrum of ozone, 16O 3, has been recorded by CW-cavity ring down spectroscopy in the 6625–6830 cm −1 region. The typical sensitivity of these recordings ( α min ∼ 3 × 10 −10 cm −1) allows observing very weak transitions with intensity down to 2 × 10 −28 cm/molecule. 483 and 299 transitions have been assigned to the 2 ν 1 + 3 ν 2 + 3 ν 3 A-type band and to the 2 ν 1 + 4 ν 2 + 2 ν 3 B-type band, respectively, which are the highest frequency bands of ozone recorded so far under high resolution. Rovibrational transitions with J and K a values up to 46 and 12, respectively, could be assigned. Despite well-known difficulties to correctly reproduce the energy levels not far from the dissociation limit, it was possible to determine the parameters of an effective Hamiltonian which includes six vibrational states, four of them being dark states. The line positions analysis led to an rms deviation of 8.5 × 10 −3 cm −1 while the experimental line intensities could be satisfactorily reproduced. Additional experiments in the 5970–6021 cm −1 region allows detecting the (233) ← (010) hot band reaching the same upper state as the preceding cold band. From the effective parameters of the (233) state just determined and those of the (010) level available in the literature, 329 transitions could be assigned and used for a further refinement of the rovibrational parameters of the effective Hamiltonian leading to a value of 7.6 × 10 −3 cm −1 for the global rms deviation. The complete list of the experimentally determined rovibrational energy levels of the (233), (242), and (520) states is given. The determined effective Hamiltonian and transition moment operators allowed calculating a line list (intensity cut off of 10 −28 cm/molecule at 296 K), available as Supplementary material for the 6590–6860 and 5916–6021 cm −1 regions. The integrated band strength values are 1.75 × 10 −24 and 4.78 × 10 −25 cm/molecule at 296 K for the 2 ν 1 + 3 ν 2 + 3 ν 3 A-type band and to the 2 ν 1 + 4 ν 2 + 2 ν 3 B-type band, respectively, while the band intensity value of the (233) ← (010) is estimated to be 1.03 × 10 −24 cm/molecule.

Study of singlet-triplet transitions in the ozone molecule using the multiconfigurational self-consistent field theory

The intensities and dipole moments of the lower singlet-triplet transitions 3 A 2 X 1 A 1 and 3 B 1 X 1 A 1 in the ozone molecule were calculated by the multiconfiguration self-consistent field theory with the quadratic response function. The results of calculations of the intensities of singlet-triplet transitions using different basis sets and complete active spaces were compared. The assignment of the 3 A 2 X 1 A 1 transition in the ozone spectrum to the Wulf band is discussed.

Threshold photoelectron spectroscopy of ozone

Threshold photoelectron spectrum of ozone is presented for the first time at a resolution of 21-38 meV using synchrotron radiation in the energy region of 12-21 eV. The ionization energies of the first ionized states were determined and an interpretation of the O3 spectrum with respect to its first three ionic states, 1 2A1, 1 2B2, and 1 2A2, is presented. Above 16 eV the enhancement of the intensities of the 2 2B1, 3 2A1, and 4 2B2 band systems due to the contribution of indirect processes was observed, not accessible by conventional photoelectron spectroscopy. It was also resolved and assigned the extensive vibrational structures of ozone. Between 15.5 and 18.5 eV the main band contours are similar to those found in conventional photoelectron spectroscopy, except that our threshold photoelectron spectrum reveals extensive additional vibrational structures. The band 2 2B1 was found to present an irregular vibrational spacing DeltaE, with a minimum value of 80 meV at approximately 16.47 eV.

Open path atmospheric spectroscopy using room temperature operated pulsed quantum cascade laser

We report the application of a distributed feedback quantum cascade laser for 5.8 km long open path spectroscopic monitoring of ozone, water vapor and CO 2. The thermal chirp during a 140 or 200 ns long excitation pulse is used for fast wavelength scanning. The fast wavelength scanning has the advantage of the measured spectra not being affected by atmospheric turbulence, which is essential for long open path measurements. An almost linear tuning of about 0.6 and 1.2 cm −1 is achieved, respectively. Lines from the ν 3 vibrational band of the ozone spectra centered at 1031 and 1049 cm −1 is used for ozone detection by differential absorption. The lowest column densities (LCD) for ozone of the order of 0.3 ppm m retrieved from the absorption spectra for averaging times less than 20 s are better then the LCD value of 2 ppm m measured with UV DOAS systems. The intrinsic haze immunity of mid-IR laser sources is an additional important advantage of mid-IR open path spectroscopy, compared with standard UV–vis DOAS. The third major advantage of the method is the possibility to measure more inorganic and organic atmospheric species compared to the UV–vis DOAS.

Vibrationally excited ozone in the middle atmosphere

Daytime mesospheric limb emission spectra of ozone in the 4.8 μ m regime are analyzed with respect to vibrational excitation and relaxation processes. The data, which was obtained by the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) instrument on board ESA's Environmental Satellite, is simulated by means of a non-local thermodynamic equilibrium (non-LTE) model utilizing O 3 -abundance, temperature, and pressure data from simultaneous retrievals in other spectral regions. The vibrational states of ozone depart from LTE due to the absorption of radiation from the lower atmosphere and due to the production of excited states in the O + O 2 + M → O 3 ( v ) + M recombination reaction. The energy flow into the ozone molecule as well as the collisional relaxation are highly uncertain. Model calculations that assume ozone formation at energies larger than 5000 cm - 1 underestimate the measured radiances by a factor of 2–3 in the 50–75 km altitude regime, if the nominal relaxation scheme is assumed. Agreement between measured and modeled radiances is achieved, if the collisional rates for the transformation of hot band stretching to bending quanta are reduced by about a factor of three, or if the quasi-nascent distribution of ozone favors vibrational states in the 3000 cm - 1 region.

Open-path ozone detection by quantum-cascade laser

Open-path ozone measurements performed by mid-IR differential absorption spectroscopy are reported. Ozone spectrum was taken by fast repetitive sweeping of a quantum-cascade laser wavelength over a spectral feature from the ν3 absorption band of ozone, centered at 1031.2 cm-1. Short (100 ns) sweeping times were essential to prevent line-distortions caused by atmospheric turbulence. For fast wavelength sweeping, a technique that employed the thermal chirp during 140 ns excitation pulses was used. The lowest detection limit of 0.3 ppm.m was estimated from the minimum detectable differential absorption. We present the results from cell and open-path measurements over 440 and 5800 m, together with experimental data regarding the tuning range, the tuning rate and the tuning linearity of the QCL while operated with 140 ns excitation pulses.

Infrared spectrum of cyclic ozone: A theoretical investigation

The infrared absorption spectrum of cyclic ozone is calculated by means of a new ab initio potential energy surface, the dipole moment function, and exact quantum mechanical dynamics calculations. Five different isotopomers are considered. The absorption line for excitation of the bending fundamental near 800 cm(-1) is by far the strongest band; all other bands are more than one order of magnitude less intense. This spectral pattern as well as the isotope shifts for the various isotopomers are important for identifying cyclic ozone. Several possibilities for accessing the ring minimum of cyclic ozone are also discussed on the basis of recent electronic structure calculations.

Intercomparison of Simultaneously Obtained Infrared (4.8 μm) and Visible (515−715 nm) Ozone Spectra Using ACE-FTS and MAESTRO

Laboratory ozone absorption spectra were measured simultaneously in the visible (515-715 nm) and infrared (2070-2140 cm(-1)) spectral regions using SCISAT-1's MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) spectrometers. An intercomparison of these measurements was used to assess the relative accuracy of HITRAN absolute line strengths, for which there was a 4% change between the 2000 and 2004 versions. Results reported here show that Chappuis band cross section strengths are more consistent with the HITRAN 2004 4.8 microm band line strengths than with the 2000 compilation.

Microwave Fourier transform, millimeterwave, and submillimeterwave spectra of ozone in its vibrational ground state

Microwave Fourier transform, millimeterwave, and submillimeterwave spectra of ozone in its vibrational ground state

Measurement of atmospheric monoaromatic hydrocarbons using differential optical absorption spectroscopy: Comparison with on-line gas chromatography measurements in urban air

Abstract A Long Path DOAS system (GIST LP-DOAS) developed by GIST has been used to simultaneously measure atmospheric monoaromatic hydrocarbons (MAHC) and other trace compounds. The validity of GIST LP-DOAS in measuring atmospheric MAHC was tested over 740 m beam paths at an urban site in Seoul, Korea, during two field campaigns held in February 2003. In order to remove the effects of interfering compounds (such as oxygen, ozone, and sulfur dioxide), two oxygen optical density spectra at two path lengths and the reference spectra of sulfur dioxide and ozone were incorporated in the fitting procedure for the determination of MAHC. The mean concentrations of MAHC measured with LP-DOAS system during the measurement period were 0.77 (benzene), 3.68 (toluene), 0.41 (p-xylene), and 0.54 ppbv (m-xylene), respectively. The results of our LP-DOAS measurements were compared with those obtained by a collocated on-line Gas Chromatography (on-line GC) system. The concept of a percent difference (PD) and linear regression methods were employed to explain the bias structure between LP-DOAS and on-line GC. The results of this comparative analysis indicated that both systems exhibited strong compatibility with relatively good correlation. According to our correlation analysis between PD values and meteorological parameters, the compatibility between the two systems increased under the conditions of improved visibility and meteorological homogeneity (wind speed >1.3 ms−1). Based on our study, it is concluded that the LP-DOAS system can be used to provide reliable information on both mixing ratios and temporal distribution characteristics of MAHC in urban air.

Structures and excitation energies of ozone–water clusters O 3(H 2O) n ( n = 1–4)

Hybrid density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been carried out for ozone–water clusters O 3(H 2O) n ( n = 1–4) in order to obtain hydration effects on the absorption spectrum of ozone. The first water molecule in n = 1 is bound to the ozone molecule by an oxygen orientation form in which the oxygen atom of H 2O orients the central oxygen atom of O 3. In n = 2, the water dimer is bound to O 3 and then the cyclic structure is formed as the most stable structure. For n = 3 (or n = 4), the cyclic water trimer (or tetramer) is bound by a hydrogen bond to the ozone molecule. The TD-DFT calculations of O 3(H 2O) n ( n = 0–4) show that the first and second excitation energies of O 3 are blue-shifted by the interaction with the water clusters. The magnitude of the spectral shift is largest in n = 2, and the shifts of the excitation energies are +0.07 eV for S 1 and +0.13 eV for S 2 states. In addition to the spectral shifts (S 1 and S 2 states), it is suggested that a charge-transfer band is appeared as a low-lying excited state above the S 1 and S 2 states. The origin of the spectrum shifts was discussed on the basis of theoretical results.

Resonance spectrum and dissociation dynamics of ozone in the 3B2 electronically excited state: experiment and theory.

The rovibrational spectrum assigned to the low-lying (3)B(2) electronic state of ozone is measured with intracavity laser absorption spectroscopy. The experimental results are interpreted by means of quantum dynamical calculations on a global ab initio potential energy surface. The observed spectrum is shown to originate from the vibrational ground state in the local minimum of the (3)B(2) potential. The spectrum of short-lived resonance states in this local minimum is analyzed. Additionally, the global minimum of the surface is shown to lie in the dissociation channel in the van der Waals region. This region supports a short sequence of weakly bound vibrational states.

Preliminary results of heterodyne detection with quantum-cascade lasers in the 9 μm region

In this paper, we describe recent results in mid-infrared heterodyne detection using quantum-cascade (QC) lasers as local oscillator (LO). In the 9 μm range, the heterodyne detection technique was first developed with CO 2 lasers and then with Pb-salt diode lasers. Quantum-cascade lasers are promising high quality tunable mid-infrared sources. We developed a quantum-cascade laser based heterodyne spectrometer. Atmospheric absorption spectra of ozone are presented.

Photoacoustic detection of ozone using a quantum cascade laser

A 9.5-μm pulsed quantum cascade laser (QCL) and a differential photoacoustic (PA) detector were used to measure trace concentrations of ∼100 ppbv ozone at ambient pressure with high selectivity. The QCL was tuned by temperature variation between -41 °C and 30.6 °C and the corresponding wavelengths were determined by the PA spectrum of CO2. Good agreement was found between the measured PA spectrum and the simulated HITRAN spectrum of ozone. The PA signal showed a linear dependence on the ozone concentration in the investigated 4300–100 ppbv range. In comparison with recently published results, in which a similar QCL in combination with an optical absorption analysis technique was applied, an improvement in the ozone-detection sensitivity by a factor of about 200 was achieved.

An Integrated Sideband-Separating SIS Mixer Based on Waveguide Split Block for 100 GHz Band with 4.0–8.0 GHz IF

We have developed an integrated sideband-separating SIS mixer for the 100 GHz band based on the waveguide split block. The measured receiver noise temperatures with 4.0–8.0 GHz IF are less than 60 K in the LO frequency range of 90–110 GHz, and a minimum value of around 45 K is achieved at 100 GHz. The image rejection ratios are more than 10 dB in the frequency range of 90–110 GHz. We have installed the sideband-separating SIS mixer into an atmospheric ozone-measuring system at Osaka Prefecture University and successfully observed an ozone spectrum at 110 GHz in SSB mode. This experimental result indicates that the sideband-separating SIS mixer is very useful for astronomical observation as well as atmospheric observation.

The calibration of instruments for atmospheric ozone measurement with a sealed ozone cell: The OSIRIN/ODIN spectrograph

A new technique for the calibration of satellite instruments for atmospheric ozone measurements with a sealed ozone cell is described. Spectral measurements of the ozone absorption from a sealed gas cell are measured with a FTIR to determine the amount of ozone in the cell. The satellite instrument then views the cell against a diffuse-reflecting screen illuminated by the appropriate visible or UV source. The calibration results from the OSIRIS/ODIN spectrograph are used to demonstrate that the method works successfully. Spectral measurements of the ozone absorption from a gas cell were measured with an FTIR spectrometer to determine the amount of ozone in the cell and then used to test the performance of the OSIRIS-DM spectrograph. The ozone spectra of the Huggins and Chappuis bands that were derived from the OSIRIS measurements were found to be in good agreement with the simulated spectra of known amounts of ozone from a radiative transfer model. The measurements reported here were taken for the purpose of characterising the performance of the OSIRIS instrument at Ottawa before flight. Final measurements were also taken at Toulouse before flight in August 2000 for the purpose of calibrating the OSIRIS FM instrument. It is recommended that all future satellite instruments for measuring ozone be calibrated pre-flight using this or a similar technique. It is also recommended that all ground based ozone-monitoring instruments such as Brewer or Dobson spectrophotometers to be used for validation of satellite instruments be calibrated using this portable and inexpensive technique.

Contribution to the analysis of the predissociated rovibronic structure of the symmetric isotopomers [formula omitted] and [formula omitted] of ozone near 10,400 cm −1: [formula omitted] and [formula omitted

The absorption spectrum of ozone was recorded at low temperatures (down to −135 °C) by high resolution Fourier transform spectrometry and intra cavity laser absorption spectroscopy (ICLAS) near 10,400 cm −1. A preliminary analysis of the rotational structure of the absorption spectra of 16 O 3 and 18 O 3 shows that this spectral region corresponds to a superposition of two different electronic transitions, one with a very broad rotational structure, showing for the first time the asymmetric stretching frequency mode ν 3 of the electronic state 3 A 2 , the other formed by a completely diffuse band, probably the 2 0 1 band of a new transition due to the triplet electronic state 3 B 2 . Predissociation effects induce large broadening of the rotational lines for the transition centered at 10,473 cm −1 identified as the 3 0 2 band of the 3 A 2← X ̃ 1 A 1 electronic transition. The rotational structure cannot be analyzed directly but instead the band contour method was used to confirm the symmetry of the transition and to estimate the spectroscopic constants for the 16 O isotopomer. The origin of the band is at 10,473±3 cm −1 and the value of the 16 O 3( 3 A 2) antisymmetric stretching frequency mode is equal to 460±2 cm −1. We believe that the diffuse band is due to the 3 B 2 state and is located at about 10,363±3 cm −1 for 16 O 3 and 10,354±3 cm −1 for 18 O 3 . The isotopic rules confirm the different results obtained for 18 O 3 and 16 O 3 .

Van der Waals states in ozone and their influence on the threshold spectrum of O3(X 1A1). I. Bound states

Threshold spectra of several isotopomers of ozone are studied using accurate quantum mechanical calculations and an ab initio potential energy surface. Shallow van der Waals minima in the dissociation channels, separated from the deep main wells by an 80 cm−1 high barrier, are shown to accommodate long progressions of assignable states. As a result, dense vibrational spectrum of ozone near dissociation is dominated by van der Waals-type states for all studied isotope compositions.