Absorption Spectrum Of Ozone Research Articles

Re-analysis of the ultraviolet absorption spectrum of ozone

A re-analysis of the Huggins and Hartley bands in the ultraviolet absorption spectrum of O3 is presented in which the structure in both bands is assigned to vibrational progressions in the symmetric stretching mode ν1 and the bending mode ν2 but not the asymmetric stretching mode ν3. The present improved fit of a larger range of bands results in relatively large anharmonicity terms, whereas previous assignments have relied on the motion being largely harmonic in the upper state. From a consideration of the shape of single surface required to support both sets of vibrational data, it is concluded that the Huggins bands almost certainly terminate on the 2 1A1 state rather than the 1 1B2 state.

Vibrational progressions in the visible and near-ultraviolet absorption spectrum of ozone

In this Letter, we have recorded and analyzed new absorption spectra of ozone (215–2400 nm) at temperatures between 203 and 293 K. Two vibrational progressions have been identified in the visible part of the spectrum between 375 and 505 nm, leading to vibrational assignments, upper state's vibrational frequencies and anharmonic coupling constants, and to an estimation of the vertical electronic energy of the 1 B 1 state, in overall agreement with recent theoretical predictions and with measurements of isotopic shifts at lower energies that were available in the literature.

A new accurate wavelength calibration for the ozone absorption cross section in the near‐UV spectral region, and its effect on the retrieval of BrO from measurements of zenith‐scattered sunlight

Measurements of BrO in the atmosphere are now routinely made using UV absorption spectroscopy, but it has recently been noted that the retrieved BrO amounts are critically dependent on the wavelength dependence of the ozone absorption cross sections used in the retrieval procedure (ozone absorbs in the same wavelength region and must therefore be accounted for in the analysis). Although atmospheric BrO measurements are typically made at a spectral resolution of ∼1 nm, it has been shown that an inaccuracy of just 0.02 nm in the wavelength calibration of the ozone cross section can result in large errors in the retrieved BrO amount. Ozone absorption cross sections calibrated to <10−3 nm are presented here in the wavelength region generally used for the retrieval of BrO from observations of scattered solar radiation (345–360 nm), and for a wide range of temperatures (223–292 K). This level of accuracy in the wavelength calibration was achieved using Fourier transform spectroscopy, to record ozone absorption spectra at a maximum instrument resolution of 1.0 cm−1. Comparisons of these well‐calibrated cross sections with those currently in general use for measurements of BrO, that is, those measured for the Global Ozone Monitoring Experiment (GOME) satellite instrument, reveal that the GOME cross sections must be shifted by an amount in the range +0.02 to +0.03 nm in order to correct their wavelength calibration. This correction to the wavelength calibration is shown to result in a significant reduction (10–20%) in the column amounts of BrO retrieved from ground‐based measurements of zenith‐scattered sunlight. An additional decrease of 5–10% is seen when the high‐resolution cross sections reported here replace the GOME wavelength‐corrected cross sections in the analysis procedure, reducing estimates of total atmospheric BrO correspondingly.

Retrieval of Ozone-Density and Atmospheric-Temperature Profiles using the Spectra of Microwave Absorption in Two Rotational Ozone Lines

We show the possibility of retrieving ozone-density and atmospheric-temperature profiles using the measurements of ozone absorption spectra in two lines with different temperature dependences. Using ozone absorption line measurements with an accuracy that can actually be reached in modern experiments, we demonstrate the possibility of retrieving few points in ozone-temperature and ozone-density profiles with vertical resolution of the order of 6 km, which is usual for microwave sounding.

Near infrared absorption spectra of ozone by high resolution Fourier transform spectrometry

We are particularly interested in the lowest lying excited electronic states that determine absorption in the Near InfraRed up to visible region. Some of them (metastable) could be sufficiently long-lived to constitute a potentially important atmospheric reservoir of “hidden” energetic ozone that may play a significant role in ozone recombination kinetics. They also could be responsible for a number of anomalies in O − O2 photochemistry including kinetics as well as isotopic enrichment [3].

Near-ultraviolet evanescent-wave absorption sensor based on a multimode optical fiber.

Fiber-optic near-ultraviolet evanescent-wave sensors have been constructed, and their feasibility for practical applications has been demonstrated. The sensors, used for the detection of ozone near the 254-nm peak of the Hartley absorption band, were fabricated from coiled segments of low-cost multimode plastic-clad silica optical fibers. The sensing sections were produced alternatively by stripping only the protective jacket from the fiber to expose the gas-permeable silicone cladding or by stripping the jacket and the cladding to expose the bare-silica fiber core. Response characteristics are given, including sensitivity to ozone, reversibility, and aging effects. The useful lifetime was unacceptably short for the sensor that employed the bare-silica core, whereas the exposed-cladding sensor demonstrated good stability over the entire two-month period of investigation. The latter, more useful sensor demonstrated a linear response to ozone over the range 0.02-0.35 vol% and a reversible response with a time constant on the order of 1 min. Differences in ozone absorption spectra obtained in the transmission and evanescent-wave modes are discussed. Projected applications of the new exposed-cladding sensor include ozone determination in water-treatment processes and ozone production plants.

Temperature Dependence of Air-Broadening and Shift Coefficients of O3Lines in the ν1Band

High-resolution Fourier transform absorption spectra of ozone broadened by dry air have been recorded at a number of temperatures from −63°C to 29°C. Using a multispectrum nonlinear least-squares procedure, we fit 29 of these spectra simultaneously to determine the air-broadening and shift coefficients and their temperature dependences for 450 lines in the 9-μm region; most of these belong to the ν1band. Partial air-broadening results were obtained for 104 additional lines, and room-temperature self-broadening coefficients were also determined for most of the 554 lines measured. These results cover a wide range of rotational quantum numbers, particularly in theRbranch, withJ″ ≤ 55 andKa″≤ 12. The variation of the retrieved broadening and shift parameters with the rotational quantum numbers has been examined; particularly interesting behavior of the broadening coefficients is noted as the value ofKa″approaches that ofJ″. The broadening and shift coefficients compare well with previous room-temperature measurements in the ν1and other bands. The temperature-dependence results are also consistent (within the stated uncertainties) with the few previous measurements of the temperature dependence of air- and N2-broadening coefficients in other O3bands, but disagree with the mean value given in the HITRAN compilation.

UV absorption spectrum of ozone: structure analysis and study of the isotope effect in the Hartley system

Apart from its crucial role in the atmosphere, particularly in filtering solar radiation in the UV wavelength region by absorption in the well known Hartley and Huggins bands, ozone attracts spectroscopic interest regarding the interpretation of these bands. From the results of previous measurements in our laboratory, we have investigated the structures of the Hartley system for two isotopes ( 16O 3 and 18O 3). This analysis allows us to propose an absolute assignment and to give two sets of vibrational parameters for the excited electronic state of the two species.

Temperature dependence of the ozone absorption spectrum over the wavelength range 410 to 760 nm

The ozone, O3, absorption cross sections between 410 and 760 nm, the Chappuis band, were measured at 220, 240, 260, and 280 K relative to that at room temperature using a diode array spectrometer. The measured cross sections varied very slightly, <1%, with decreasing temperature between 550 and 660 nm, near the peak of the Chappuis band. At wavelengths away from the peak, the absorption cross sections decreased with decreasing temperature; e.g., ∼40% at 420 nm between 298 and 220 K. These results are compared with previous measurements and the impact on atmospheric measurements are discussed.

Measurements of Pressure Broadening and Shifts of O3 Lines in the 3-μm Region

We have recorded high-resolution Fourier transform absorption spectra of ozone broadened by dry air, by N2, or by O2 at room temperature. From these spectra we have determined pressure-broadening and line-shift coefficients for over 270 lines in the ν1 + ν2 + ν3 and 3ν3 bands. The Lorentz broadening coefficients obtained in these bands are similar to those determined from measurements in the ν1, ν3, and ν1 + ν3 bands. However, there is some evidence for a small vibrational dependence of the broadening coefficients. As expected, the pressure-induced lineshifts determined in the 3-μm hands are significantly larger than those observed in the 4.8- and 9-μm regions.

An assignment of the structured features in the Hartley band absorption spectrum of ozone

Using recent experimental data for the Hartley band absorption spectrum obtained at low temperature, a vibrational analysis of the discrete structure in the spectrum is given. It is found that all of the peaks in the range 238–292 cm can be assigned to transitions between the (0,0,0) vibrational state in the ground electronic state and (v1′,v2′) vibrational states in the upper electronic state. The observed structure in the Hartley band is due to a long progression in the symmetric stretching mode, and a shorter progression in the bending mode. Based on the vibrational assignment, the following information is obtained on the vibrational parameters and geometry of ozone in the 1B2 electronic state (all parameters are given for C2v symmetry): ω1′ = 1108 ± 25 cm−1, ω1′x1′ = 9 ± 3 cm−1, ω2′ = 298 ± 12 cm−1, ω3′ = (1650 ± 300)i cm−1, r00=0.140±0.002 nm, φ=105±2°. The analysis that is presented demonstrates that residual vibrational structure can occur in dissociative transitions, confirming previous suggestions.

ChemInform Abstract: Rotational Structure in the Near‐IR Absorption Spectrum of Ozone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rotational structure in the near-infrared absorption spectrum of ozone

Ozone absorption spectra near 1 μm exhibit fine structure indicative of rotational subbands, suggesting that the upper electronic state is metastable. Preliminary analysis supports a previous assignment to the 3A2←1A1 transition. A binding energy of ∼0.1 eV is inferred from the breakoff in the observed structure.

Ozone depletion and its effects on human populations.

Concern about the ozone-depleting potential of man-made chemicals has led the United Nations to control their usage. Under the present arrangements, fully halogenated chlorofluorocarbons, halons and carbon tetrachloride will be phased out by the year 2000, and methylchloroform by the year 2005. Even so, atmospheric chlorine is expected to rise to seven times its natural level, so further ozone losses and greater ultraviolet B (UVB) exposure can be expected over heavily populated areas of the globe. Calculating changes in skin cancer incidence is a two-stage process which must take account of the increase in biologically effective UVB that results from an ozone loss of 1% (optical amplification factor, OAF) and the percentage increase in skin cancer incidence that results from a 1% increase in annual UV dose (biological amplification factor, BAF). Epidemiological data provide a BAF value of approximately 1.7 for basal cell carcinoma and 3.0 for squamous cell carcinoma. The absorption spectrum of ozone and the increased carcinogenic impact of UV radiation around 300 nm results in a value for OAF of approximately 1.6%; thus a 10% loss of ozone, if sufficiently sustained, would eventually increase the incidence of basal and squamous cell carcinomas by almost 30% and 50%, respectively. Dermatologists, therefore, need to look carefully at the environment in order to safeguard the health of future generations.

Near-ultraviolet spectroscopy of Comet Austin (1989c1)

Comet Austin (1989c1) was observed post-perihelion at a heliocentric distance near 1.25 AU. The wavelength range was from the atmospheric cutoff at 3000 to 4000 A. The coma spectra were calibrated into flux units and the contaminating sky spectrum and solar scattered light continuum were subtracted, leaving an ultraviolet spectrum of about 1.5-A resolution and excellent signal-to-noise ratio. The spectrum is dominated by emissions from OH, NH, CH, C3, and CN, some of the weaker emissions of which are seen here for the first time. More bands of CO(2+) were found than in any previous investigation and several intensity anomalies were noted; H2CO, OH(+), NCN, N(2+), and CN(+) may be present. Several emission features well above the noise level remain unidentified. The relative intensities of the OH and CN bands agree with the predictions of resonance fluorescence when one considers the potential effects of contamination by other molecules. The effects of the ozone absorption spectrum are not fully removed by the data-reduction process, although this does not affect these results.

Effect of isotopic substitution on the visible absorption spectrum of ozone

Absorption spectra for 16O3 and 18O3 have been recorded to study the vibronic structure of the Chappuis band. The isotope shifts indicate that the strongest features involve transitions to two electronically excited states characterized by adiabatic energies ≊750 cm−1 apart, with the higher one near 16 400 cm−1. The vibrational structure can be associated with a relatively simple progression in this higher state (ω1 and ω2≊1210 and 640 cm−1, respectively), and one isolated band associated with the lower state. Alternatively, an autocorrelation analysis indicates major recurrences near 31 and 41 fs for 16O3, and correspondingly longer times for 18O3. Minor recurrences at longer times are also present, but all are significantly shorter lived than those associated with the Hartley band. The results are discussed in the context of ab initio calculations and recent experimental and theoretical work involving visible and ultraviolet absorption spectra of ozone.

Measurements of self-broadening of infrared absorption lines of ozone

Lorentz self-broadening coefficients have been determined for 355 spectral lines belonging to five different infrared vibration-rotation bands of O 3 in the spectral region from 4.8 to 17 μm. Six ozone absorption spectra, recorded at room temperature using a Fourier transform spectrometer, were analyzed. The half-width values were obtained through a nonlinear least-squares spectral fitting procedure. The results are compared with previous measurements, and the variation of the half-widths with vibrational and rotational quantum numbers is examined.

Line positions and intensities for the ν2 + 3 ν3 band of 16O 3 around 2.7 μm

The absorption spectrum of ozone has been recorded between 3600 and 3900 cm −1 at 0.01 cm −1 resolution with a Fourier transform spectrometer. The analysis of the spectra has allowed the first high-resolution study of the ν 2 + 3 ν 3 band of the 16O 3 molecule. The experimental rotational energy levels of the (013) vibrational state have been measured up to J = 40 and K a = 13 allowing an accurate set of rotational constants to be determined with a Hamiltonian taking into account the Coriolis resonances with the unobserved (112) vibrational state. Moreover, 71 line intensities measured with a relative uncertainty of about 8% were least-squares fitted leading to the determination of the main ν 2 + 3 ν 3 transition moment constants. Finally, a complete list of line positions, intensities, and lower state energies was generated for the ν 2 + 3 ν 3 and ν 1 + ν 2 + 2 ν 3 bands of 16O 3.

Stratospheric ozone measurements with a tunable diode laser heterodyne spectrometer

The vertical mixing ratio profiles of stratospheric ozone have been obtained through an inversion of the ozone absorption spectra in the 9µm band measured by a tunable diode laser heterodyne spectrometer with a spectral resolution of 80 MHz (0.0027 cm−1). The observations were made on June 22, 1988, and on August 22, 1988, at Sendai (38°15′N, 140°50′E), Japan. The values of the signal‐to‐noise ratio of the observed spectra are 190 for the data of June 22, 1988, and 300 for the data of August 22, 1988. The accuracy of the mixing ratio and the vertical resolution is examined. The results are compared with data obtained by Dobson spectrophotometers and an ozonesonde.

Adjustable-temperature and multiple-path optical cell for ozone spectroscopy

The authors describe an absorption cell suitable for recording infrared spectra. The optical path can be adjusted between 1 and 10 m. The temperature is variable in the range 200-400 K. This stainless steel cell has been especially designed for ozone. A 10 mu m ozone absorption spectrum is presented as an example.