Bands Of O2 Research Articles

VUV-Photoluminescence Properties of (Gd, La)<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>: Eu<sup>3+</sup>

(Gd,La)2-x O2CO3:Eux3+(0.01 ≤x≤0.04) were synthesized via a flux method at 400°C, and their photoluminescence properties under vacuum ultraviolet (VUV) excitation were examined. The excitation spectra showed two bands in the region from 125 nm to 300 nm, the first band centered at 190 nm was ascribed to absorption of related CO32- complex, and the second broad band centered at 246nm and 278nm in Gd2O2CO3:Eu3+ was ascribed to the charge transfer band of O2-→ Eu3+. Series samples exhibited red emission at around 611 nm under vacuum ultraviolet excitation corresponding to the 5D0→ 7F2.transition of Eu3+.

Accuracy analysis of PPDF-based method to parameterize aerosol scattering effect

We introduce the path length probability density function (PPDF) method, which is based on an equivalence theorem and parameterizes the aerosol scattering effect by adding four factors to the atmospheric transmittance model. Using simulated observations in the O2-A band, we examined the utility of the PPDF-based method to account for the aerosol scattering effect. First, observations were simulated using a forward model under different aerosol conditions; PPDF factors were then retrieved using an optimal estimation method; PPDF factors were used to reconstruct the observations; and finally, simulated true observations and reconstructions were compared. Analysis of the difference between the true observations and reconstructions confirmed the utility of the PPDF-based method. Additionally, the O2 band was demonstrated to be an efficient observing band for assisting the remote sensing of atmospheric trace gases in the near-infrared band.

Synthesis and Luminescence Properties of Ba<sub>3</sub>Y<sub>1</sub><sub>-</sub><i><sub>x</sub></i>Eu<i><sub>x</sub></i>B<sub>3</sub>O<sub>9 </sub>(0.05≤<i>x</i>≤0.35) under UV Excitation

Single phase of Ba3Y1-xEuxB3O9 (0.05 ≤ x≤ 0.35)samples was prepared by the solid state reaction. The crystal structure, the surface, the particle size and luminescence properties were characterized by X-ray diffractometer, scanning electron microscopy and spectrophotometer. The results showed that the obtained samples with the particle size from 0.3 to 1.5 um were hexagonal structure. Monitored by 592 nm emission, the excitation spectra of Ba3Y1-xEuxB3O9were dominated by the charge transfer band of O2-→Eu3+ peaking at about 259 nm until x= 0.15; the transition from 7F0 to 5L6 level of Eu3+ at about 395 nm was maximum after x> 0.15. The strongest emission peak due to the 5D0→7F1transition of Eu3+ was all located at about 592 nm in the emission spectra of Ba3Y1-xEuxB3O9, and the maximum emission was obtained at x= 0.15 and 0.3 under 254 and 395 nm excitation, respectively. The excitationprocess under the two excitation energies was analyzed. It indicated that only the centrosymmetric lattices could be excited under 254 nm excitation; both the centrosymmetric and noncentrosymmetric positions could be excited by 395 nm, accordingly, the ratio of the red emission (5D0→7F2) to the orange one (5D0→7F1) increased, leading to a better chromaticity of the phosphors.

Highly accurate potential energy surface, dipole moment surface, rovibrational energy levels, and infrared line list for 32S16O2 up to 8000 cm−1

A purely ab initio potential energy surface (PES) was refined with selected (32)S(16)O2 HITRAN data. Compared to HITRAN, the root-mean-squares error (σ(RMS)) for all J = 0-80 rovibrational energy levels computed on the refined PES (denoted Ames-1) is 0.013 cm(-1). Combined with a CCSD(T)/aug-cc-pV(Q+d)Z dipole moment surface (DMS), an infrared (IR) line list (denoted Ames-296K) has been computed at 296 K and covers up to 8000 cm(-1). Compared to the HITRAN and CDMS databases, the intensity agreement for most vibrational bands is better than 85%-90%. Our predictions for (34)S(16)O2 band origins, higher energy (32)S(16)O2 band origins and missing (32)S(16)O2 IR bands have been verified by most recent experiments and available HITRAN data. We conclude that the Ames-1 PES is able to predict (32/34)S(16)O2 band origins below 5500 cm(-1) with 0.01-0.03 cm(-1) uncertainties, and the Ames-296K line list provides continuous, reliable and accurate IR simulations. The K(a)-dependence of both line position and line intensity errors is discussed. The line list will greatly facilitate SO2 IR spectral experimental analysis, as well as elimination of SO2 lines in high-resolution astronomical observations.

Facile and green synthesis of (La0.95Eu0.05)2O2S red phosphors with sulfate-ion pillared layered hydroxides as a new type of precursor: controlled hydrothermal processing, phase evolution and photoluminescence

This study presents a facile and green route for the synthesis of (La0.95Eu0.05)2O2S red phosphors of controllable morphologies, with the sulfate-type layered hydroxides of Ln2(OH)4SO4·2H2O (Ln = La and Eu) as a new type of precursor. The technique takes advantage of the fact that the precursor has had the exact Ln:S molar ratio of the targeted phosphor, thus saving the hazardous sulfurization reagents indispensable to traditional synthesis. Controlled hydrothermal processing at 120 °C yielded phase-pure Ln2(OH)4SO4·2H2O crystallites in the form of either nanoplates or microprisms, which can both be converted into Ln2O2S phosphor via a Ln2O2SO4 intermediate upon annealing in flowing H2 at a minimum temperature of ∼ 700 °C. The nanoplates collapse into relatively rounded Ln2O2S particles while the microprisms retain well their initial morphologies at 1 200 °C, thus yielding two types of red phosphors. Photoluminescence excitation (PLE) studies found two distinct charge transfer (CT) excitation bands of O2− → Eu3+ at ∼ 270 nm and S2− → Eu3+ at ∼ 340 nm for the Ln2O2S phosphors, with the latter being stronger and both significantly stronger than the intrinsic intra-f transitions of Eu3+. The two types of phosphors share high similarities in the positions of PLE/PL (photoluminescence) bands and both show the strongest red emission at 627 nm (5D0 → 7F2 transition of Eu3+) under S2− → Eu3+ CT excitation at 340 nm. The PLE/PL intensities show clear dependence on particle morphology and calcination temperature, which were investigated in detail. Fluorescence decay analysis reveals that the 627 nm red emission has a lifetime of ∼ 0.5 ms for both types of the phosphors.

Chemical bond properties and charge transfer bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) in Eu(3+)-doped garnet hosts Ln3M5O12 and ABO4 molybdate and tungstate phosphors.

Charge transfer (CT) energy from the ligand to the central ions is an important factor in luminescence properties for rare earth doped inorganic phosphors. The dielectric theory of complex crystals was used to calculate chemical bond properties. Combining the photoluminescence and the dielectric theory of complex crystals, the CT bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) for Eu(3+)-doped inorganic phosphors have been investigated experimentally and theoretically. Taking Eu(3+)-doped Ln3M5O12 (Ln = Y, Lu and M = Al, Ga), Gd3Ga5O12, MMoO4 (M = Ca, Sr, Ba) and MWO4 (M = Ca, Sr, Ba) as typical phosphors, we investigated the effects of the cation size on the CT bands and chemical bond properties including the bond length (d), the covalency (fc), the bond polarizability (αb) and the environmental factor (he) of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+), respectively. For systematic isostructural Ln3M5O12 (Ln = Y, Lu and M = Al, Ga) phosphors, with the increasing M ion radius, the bond length of Ln-O decreases, but fc and αb increase, which is the main reason that the environmental factor increased. For the isostructural MMoO4:Eu, with the increasing M ion radius, the Mo-O bond length increases, but fc and αb decrease, and thus he decreases. However, in the compound system MWO4:Eu (M = Ca, Ba) with the increasing M ion radius, the O-W bond length increases, but fc and αb increase, and thus he increases and the O-W CT energy decreases. Their O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) CT bands as well as their full width at half maximum (FWHM) were directly influenced by he. And with the increasing he, CT bands of O-Eu or O-Mo or O-W decrease and their FWHM increases. These results indicate a promising approach for changing the material properties, searching for new Eu(3+) doped molybdate, tungstate or other oxide phosphors and analyzing the experimental result.

Ground-based airglow imaging interferometer. Part 1: instrument and observation.

A ground-based airglow imaging interferometer (GBAII) is proposed to measure simultaneously the temperature and wind in the mesopause region by using airglow emissions of the O2(0-1) band. Since it employs a wide angle Michelson interferometer with a large air gap, combined with the rotational temperature measurement, both the phase and spectral information can be obtained from the imaging results. Based on the optimization and calibrations for the optical system in the laboratory, we developed and assembled a prototype of a GBAII, and carried out one observation at the observatory of Xi'an University of Technology on 12 June 2012. The observed temperatures fall mainly on the range of 167-196K, while both the zonal and meridional winds faintly show the feature of half-day oscillation. The consistent trends between the observation results and the standard atmospheric models suggest that the GBAII has achieved our basic design goals.

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

Context. Clouds play an important role in the radiative transfer of planetary atmospheres because of the influence they have on the different molecular signatures through scattering and absorption processes. Furthermore, they are important modulators of the radiative energy budget affecting surface and atmospheric temperatures.Aims. We present a detailed study of the thermal emission of cloud-covered planets orbiting F-, G-, K-, and M-type stars. These Earth-like planets include planets with the same gravity and total irradiation as Earth, but can differ significantly in the upper atmosphere. The impact of single-layered clouds is analyzed to determine what information on the atmosphere may be lost or gained. The planetary spectra are studied at different instrument resolutions and compared to previously calculated low-resolution spectra.Methods. A line-by-line molecular absorption model coupled with a multiple scattering radiative transfer solver was used to calculate the spectra of cloud-covered planets. The atmospheric profiles used in the radiation calculations were obtained with a radiative-convective climate model combined with a parametric cloud description.Results. In the high-resolution flux spectra, clouds changed the intensities and shapes of the bands of CO2 , N2 O, H2 O, CH4 , and O3 . Some of these bands turned out to be highly reduced by the presence of clouds, which causes difficulties for their detection. The most affected spectral bands resulted for the planet orbiting the F-type star. Clouds could lead to false negative interpretations for the different molecular species investigated. However, at low resolution, clouds were found to be crucial for detecting some of the molecular bands that could not be distinguished in the cloud-free atmospheres. The CO2 bands were found to be less affected by clouds. Radiation sources were visualized with weighting functions at high resolution.Conclusions. Knowledge of the atmospheric temperature profile is essential for estimating the composition and important for avoiding false negative detection of biomarkers, in both cloudy and clear-sky conditions. In particular, a pronounced temperature contrast between the ozone layer and surface or cloud is needed to detect the molecule. Fortunately, the CO2 bands allow temperature estimation from the upper stratosphere down to the troposphere even in the presence of clouds.

Photoluminescence properties of MgY4Si3O13:Gd3+, Tb3+ under vacuum ultraviolet excitation

Gd3+ and Tb3+ co-doped MgY4Si3O13 green phosphors were prepared by a solid-state reaction. The photoluminescence properties in vacuum ultraviolet–visible (VUV–vis) range and decay properties were investigated in details. The f–d transition of Gd3+ ions and spin-allowed f–d transition of Tb3+ ions locate at about 134nm and 239nm, respectively. Two charge transfer bands of O2−→Gd3+ and O2−→Tb3+ overlap at about 155nm. Some f–f transition of Tb3+ and Gd3+ ions are confirmed in VUV–vis range. Upon excitation at 172nm, the optimal composition of MgY3.3Si3O13:0.5Gd3+, 0.2Tb3+ phosphor exhibits the characteristic transitions of Gd3+ and Tb3+ with chromaticity coordinate of (0.2849, 0.5843). The phosphor has a shorter decay time (2.13ms) than that of Zn2SiO4:Mn2+ (4.56ms). The results suggest that this green phosphor is a potential candidate for mercury-free luminescence lamps and plasma display panels (PDPs) application.

Cross-band relative absorption technique for the measurement of molecular mixing ratios

We describe a new method for the measurement of molecular mixing ratios called Cross-Band Relative Absorption (CoBRA). The proposed method is based on relative measurements in different molecular bands referenced to a band of O2 with properly selected wavelength combinations providing high level of cancelation in temperature sensitivities. The CoBRA approach is particularly promising for satellite based remote sensing of molecular mixing ratios of the atmospheric trace gases. Very low temperature sensitivities and the potential of achieving close weighting function matching for the measurement and reference wavelengths are the main advantages of the method. The effectiveness of CoBRA approach is demonstrated for the retrieval of CO2 mixing ratios (XCO2) with application to the ASCENDS mission.

Developments of Optical Spectrometers as Approaches to Diffuse Interstellar Bands

AbstractA discharge-emission spectrometer and a cavity ringdown spectrometer have been developed to aid in the solution to the diffuse interstellar band (DIB) problem. A hollow cathode was used to generate molecular ions in a discharge because it has been suggested that molecular ions are probable DIB candidates. The discharge was produced by a pulsed voltage of 1300–1500 V. A wide wavelength range of optical emission from the discharge was examined by a HORIBA Jobin Yvon iHR320 monochromator. The dispersed discharge emission was detected by a photomultiplier and was recorded via a lock-in amplifier. The 2B3u–X2B2g electronic transition of the butatriene cation H2CCCCH2+ was observed in the discharge emission of 2-butyne H3CCCCH3. The frequency of the electronic transition was measured to be 20381 cm−1, and a comparison study was made with known DIB spectra.The resolution of the discharge-emission spectrometer is insufficient to make precise comparisons between laboratory frequencies and astronomically observed DIB spectra. We therefore developed the cavity ringdown spectrometer using the same hollow cathode. The high sensitivity of this spectrometer was confirmed by the observation of the forbidden band of O2.

Spectral features of Earth-like planets and their detectability at different orbital distances around F, G, and K-type stars

We investigate the spectral appearance of Earth-like exoplanets in the HZ of different main sequence stars at different orbital distances. We furthermore discuss for which of these scenarios biomarker absorption bands may be detected during primary or secondary transit with near-future telescopes and instruments.We analyze the spectra taking into account different filter bandpasses of two photometric instruments planned to be mounted to the JWST. We analyze in which filters and for which scenarios molecular absorption bands are detectable when using the space-borne JWST or the ground-based telescope E-ELT. Absorption bands of CO2, H2O, CH4 and O3 are clearly visible in high-resolution spectra as well as in the filters of photometric instruments. However, only during primary eclipse bands of CO2, H2O and O3 are detectable for all scenarios when using photometric instruments and an E-ELT telescope setup. CH4 is only detectable at the outer HZ of the K star since here the atmospheric modeling results in very high abundances. Since the detectable CO2 and H2O bands overlap, separate bands need to be observed to prove their existence in the atmosphere. In order to detect H2O in a separate band, a S/N>7 needs to be achieved for E-ELT observations, e.g. by co-adding at least 10 transit observations. Using a spaceborne telescope like the JWST enables the detection of CO2 at 4.3mu, which is not possible for ground-based observations due to the Earth's atmospheric absorption. Hence combining observations of spaceborne and groundbased telescopes might allow to detect the presence of the biomarker molecule O3 and the related compounds H2O and CO2 in a planetary atmosphere. Other absorption bands using the JWST can only be detected for much higher S/Ns, which is not achievable by just co-adding transit observations since this would be far beyond the planned mission time of JWST.(abridged)

Planetary wave induced wind and airglow oscillations in the middle latitude MLT region

Upper mesosphere airglow emissions and temperature observed at Rikubetsu (43.5°N,143.8°E) and mesospheric winds observed at Wakkanai (45.4°N,141.8°E), Japan, from January to December 2005 were used to analyze periodic oscillations of 2–16 days. During the January to March period and after September, both winds and airglow demonstrated clear 8-, 10- and 16-day oscillations. Downward phase progressions observed in the oscillations indicate that these are a signature of Rossby mode planetary waves. The 16-day wave was more evident in the zonal wind than the meridional. The 10-day wave was observed in January and March, on the basis of only a few cycles superposed on the 16-day wave. Airglow OI 557.7nm, O2 and OH(6,2) band emissions and O2 rotational temperature also showed significant amplitude of oscillation induced by the wave passages. For the 10-day wave, OI557.7nm showed an amplitude of oscillation equals to or more than 50% of the mean intensity level, O2 ∼45% and OH ∼25%. Large amplitudes of oscillation of the airglow during the passage of planetary waves suggest the possible vertical transport of atomic oxygen in addition to the density and temperature variations intrinsic to the wave events.

VARIABILITY OF WATER AND OXYGEN ABSORPTION BANDS IN THE DISK-INTEGRATED SPECTRA OF EARTH

We study the variability of major atmospheric absorption features in the disk-integrated spectra of the Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of the Earth provided by the EPOXI mission, and find 5-20% fractional variation of the absorption depths of H2O and O2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H2O and O2 bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On the Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H2O on the planet's surface on a timescale short compared to atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars

Context. The atmosphere of Earth-like extrasolar planets orbiting different types of stars is influenced by the spectral dependence of the incoming stellar radiation. The changes in structure and composition affect atmospheric radiation, hence the spectral appearance of these exoplanets.Aims. We provide a thorough investigation of infrared radiative transfer in cloud-free exoplanets atmospheres by not only analyzing the planetary spectral appearance but also discussing the radiative processes behind the spectral features in detail and identifying the regions in the atmosphere that contribute most at a given wavelength. Methods. Using cloud-free scenarios provided by a one-dimensional radiative-convective steady-state atmospheric model, we computed high-resolution infrared transmission and emission spectra, as well as weighting functions for exoplanets located within the habitable zone of F, G, K, and M stars by means of a line-by-line molecular absorption model and a Schwarzschild solver for the radiative transfer. The monochromatic spectra were convolved with appropriate spectral response functions to study the effects of finite instrument resolution.Results. Spectra of the exoplanets of F, G, K, and M stars were analyzed in the 4.5 μ m N2 O band, the 4.3 μ m and 15 μ m CO2 bands, the 7.7 μ m CH4 band, the 6.3 μ m H2 O band, and the 9.6 μ m O3 band. Differences in the state of the atmosphere of the exoplanets clearly show up in the thermal infrared spectra; absorption signatures known from Earth can be transformed to emission features (and vice versa). Weighting functions show that radiation in the absorption bands of the uniformly mixed gases (CO2 , CH4 , N2 O) and (to some extent) ozone comes from the stratosphere and upper troposphere, and also indicate that changes in the atmospheres can shift sources of thermal radiation to lower or higher altitudes. Molecular absorption and/or emission features can be identified in the high-resolution spectra of all planets and in most reduced resolution spectra. Conclusions. Insight into radiative transfer processes is essential for analyzing exoplanet spectral observations; for instance, understanding the impact of the temperature profile (nb. non-existence of an inversion) on the CO2 bands facilitates their interpretation and can help avoid false positive or negative estimates of O3 . The detailed analysis of the radiation source and sink regions could even help give an indication about the feasibility of identifying molecular signatures in cloud-covered planets, i.e. radiation mainly coming from the upper atmosphere is less likely to be hidden by clouds. Infrared radiative transfer and biomarker detectability in cloud-covered exoplanets will be presented in a companion paper.

The characteristics of the O2 Herzberg II and Chamberlain bands observed with VIRTIS/Venus Express

The oxygen Venus nightglow emissions in the visible spectral range have been known since the early observations from the Venera spacecraft. Recent observations with the VIRTIS instrument on board Venus Express allowed us to re-examine the Herzberg II system of O2 and to further study its vertical distribution, in particular the (0–ν″ with ν″=7–13) bands. The present work describes the vertical profile of the observed bands and relative intensities from limb observation data. The wavelength-integrated intensities of the Herzberg II bands, with ν″=7–11, are inferred from the recorded spectra. The resulting values lie in the range of 84–116kR at the altitudes of maximum intensity, which are found to lie in the range of 93–98km.Three bands of the Chamberlain system, centered at 560nm, 605nm, and 657nm have been identified as well. Their emission peak is located at about 100km, 4km higher than the Herzberg II bands.For the first time, the O2 nightglow emissions were investigated simultaneously in the visible and in the IR spectral range, showing a good agreement between the peak position for the Herzberg II and the O2(a1Δg–X3Σg-) bands. An airglow model, proposed by Gérard et al. (Gérard, J.C., Soret, L., Migliorini, A., Piccioni, G. [2013]. Icarus.) starting from realistic O and CO2 vertical distributions derived from Venus-Express observations, allows reproduction of the observed profiles for the three O2 systems.

Trajectory retrieval and component investigations of the southern polar stratosphere based on high-resolution spectroscopy of the totally eclipsed moon surface

In this paper we present the high-resolution spectral observations of the fragment of lunar surface during the total lunar eclipse of December 10, 2011. The observations were carried out with the fiber-fed echelle spectrograph at the 1.2-m telescope in Kourovka Astronomical observatory (Ural mountains, central Russia). The observed radiation is transmitted by tangent trajectory through the southern polar stratosphere before the reflection from the Moon and the spectra contain a number of absorption bands of atmospheric gases (O2, O3, O4, NO2, H2O). High-resolution analysis of three O2 bands and O4 absorption effects is used to trace the effective trajectory of solar emission through the stratosphere and to detect the contribution of scattered light. Bands of other gases allow us to measure their abundances along the trajectory.

Preparation and spectroscopic properties of rare-earth (RE) (RE = Sm, Eu, Tb, Dy, Tm)-activated K2LnZr(PO4)3 (Ln = Y, La, Gd and Lu) phosphate in vacuum ultraviolet region

Rare earth (RE=Sm, Eu, Tb, Dy and Tm)-activated K2LnZr(PO4)3 (Ln=Y, La, Gd and Lu) have been synthesized by solid-state reaction method, and their vacuum ultraviolet (VUV) excitation luminescent characteristics have been investigated. The band in the wavelength range of 130–157nm and the other one range from 155 to 216nm with the maximum at about 187nm in the VUV excitation spectra of these compounds are attributed to the host lattice absorption and O–Zr charge transfer transition, respectively. The charge transfer bands (CTB) of O2−Sm3+, O2−Dy3+ and O2−Tm3+, in Sm3+, Dy3+ and Tm3+-activated samples, have not been obviously observed probably because the 2p electrons of oxygen are tightly bound to the zirconium ion in the host lattice. For Eu3+-activated samples, the relatively weak O2−Eu3+ CTB at about 220nm is observed. And for Tb3+-activated samples, the bands at 223 and 258nm are related to the 4f-5d spin-allowed and spin-forbidden transitions of Tb3+, respectively. It is observed that there is energy transfer between the host lattice and the luminescent activators (e.g. Eu3+, Tb3+). From the standpoint of luminescent efficiency, color purity and chemical stability, K2GdZr(PO4)3:Sm3+, Eu3+, Tb3+ are attractive candidates for novel yellow, red, green-emitting PDP phosphors.

Validation of line and continuum spectroscopic parameters with measurements of atmospheric emitted spectral radiance from far to mid infrared wave number range

The latest release of a high-resolution transmission molecular absorption database along with two improved models of water vapor continuum absorption are used to check their impact on the improvement of state-of-art radiative transfer. Radiative transfer performance has been assessed using high mountains atmospheric emitted spectral downwelling radiance observations in the 360–1200cm−1 spectral regions. These high mountains observations are particularly suited to check the behavior and performance in the water vapor rotation band. In addition, they also have allowed us to gain insight into understanding the quality of recent new compilation of lines and related treatment for the ν2 CO2 band and the O3 band at 9.6μm. Comparisons are made between forward calculations of atmospheric transmission spectra and spectral radiances measured using two ground-based Fourier transform instruments. The results demonstrate that water vapor absorption largely benefits from the recent improvement in the related continuum (both self and foreign). In addition, ozone absorption is very accurately reproduced and, although to a less extent, this is also the case of CO2 absorption in the long wave ν2 band.

Low temperature cavity ring down spectroscopy with off-axis alignment: application to the A- and γ-bands of O2 in the visible at 90 K

The cavity ring down (CRD) technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 298 K. An off-axis alignment of the laser beam into the cavity is used to increase the number of resonant modes inside the cavity and improve the signal to noise ratio of the absorption bands. To demonstrate the capabilities of the low temperature CRD cell, the absorption spectra of O2 are recorded at 90 K for the A (υ′=0←υ″=0) and γ (υ′=2←υ″=0) bands of the \(b^{1}\sum_{g}^{ +}\leftarrow X^{3}\sum_{g}^{ -} \) transition using cavity ring down spectroscopy. The optical cavity performance was tested using two variations of the CRD technique. The A-band is measured using the phase-shift cavity ring down method and the γ-band using the pulsed-laser exponential-decay method. A comparison between experimental and simulated spectra of the O2 bands at 90 K confirms the molecular temperature measured by a sensor localized in the cell. Quantitative measurements of the individual rotational line intensities are made for the oxygen γ-band to confirm the temperature of the cell and calculate the vibrational band intensity. The application of this technique for laboratory studies of planetary atmospheres and the spectroscopy of molecular complexes is emphasized.