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Wei PS, Chiu HH, Hsieh YC, Yen DL, Lee C, Tsai YC, Ting TC. Absorption coefficient of water vapor across atmospheric troposphere layer. Heliyon 2019; 5:e01145. [PMID: 30723826 PMCID: PMC6351392 DOI: 10.1016/j.heliyon.2019.e01145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/10/2018] [Accepted: 01/15/2019] [Indexed: 11/27/2022] Open
Abstract
Absorption coefficient of water vapor proposed to be responsible for an increase in temperature in the troposphere layer with altitude less than 10 km is systematically presented in this work. Since global warming plays an important role in affecting the human life, a confirmative and detailed study of global warming is essentially need. Solar irradiation within short wavelength range can be extinguished from absorption and scattering by the atmosphere, and absorbed and reflected by the Earth's surface. Radiative within high wavelength range from the Earth's surface can be absorbed by atmospheric water vapor, carbon dioxide and other gases. The difference in solar irradiation and energy escaped to the space from the atmosphere results in the atmosphere acting as the glass of a greenhouse and increase atmospheric temperature. Extending the previous work [1] for predicting absorption coefficient of carbon dioxide through the troposphere, this work further determines absorption coefficients of water vapor in different wavelength bands centered at 71, 6.3, 2.7, 1.87 and 1.38 μm across the temperature, pressure and concentration-dependent troposphere layer. Solving one-dimensional unsteady heat conduction-radiation equation with the COMSOL computer code, the predicted temperature together with water vapor density for different optical path lengths can be used to interpret in details absorption coefficient or the ratio between band intensity and effective band width by using the exponential wide band model. The results show that absorption coefficients are strongly affected by water vapor concentration. For example, absorption coefficients in the band centered at 71 μm increases from 0.3 to 1.2 m−1 at the tropopause and 0.6 to 3.1 m−1 at the Earth's surface as mole fraction of water vapor increases from 0.005 to 0.02. The predicted absorption coefficients agree with experimental and theoretical results in the literature. A more detailed and realistic temperature profile through the troposphere with optical path length of 104 m is presented.
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Affiliation(s)
- Peng-Sheng Wei
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Hsuan-Han Chiu
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Yin-Chih Hsieh
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Da-Lun Yen
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Chieh Lee
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Yi-Cheng Tsai
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Te-Chuan Ting
- Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
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Guo Y, Sun L, Yang Z, Liu Z. Generalized design of a zero-geometric-loss, astigmatism-free, modified four-objective multipass matrix system. APPLIED OPTICS 2016; 55:1435-1443. [PMID: 26906598 DOI: 10.1364/ao.55.001435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
During this study we constructed a generalized parametric modified four-objective multipass matrix system (MMS). We used an optical system comprising four asymmetrical spherical mirrors to improve the alignment process. The use of a paraxial equation for the design of the front transfer optics yielded the initial condition for modeling our MMS. We performed a ray tracing simulation to calculate the significant aberration of the system (astigmatism). Based on the calculated meridional and sagittal focus positions, the complementary focusing mirror was easily designed to provide an output beam free of astigmatism. We have presented an example of a 108-transit multipass system (5×7 matrix arrangement) with a relatively larger numerical aperture source (xenon light source). The whole system exhibits zero theoretical geometrical loss when simulated with Zemax software. The MMS construction strategy described in this study provides an anastigmatic output beam and the generalized approach to design a controllable matrix spot pattern on the field mirrors. Asymmetrical reflective mirrors aid in aligning the whole system with high efficiency. With the generalized design strategy in terms of optics configuration and asymmetrical fabrication method in this paper, other kinds of multipass matrix system coupled with different sources and detector systems also can be achieved.
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Mlawer EJ, Payne VH, Moncet JL, Delamere JS, Alvarado MJ, Tobin DC. Development and recent evaluation of the MT_CKD model of continuum absorption. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:2520-2556. [PMID: 22547231 DOI: 10.1098/rsta.2011.0295] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Water vapour continuum absorption is an important contributor to the Earth's radiative cooling and energy balance. Here, we describe the development and status of the MT_CKD (MlawerTobinCloughKneizysDavies) water vapour continuum absorption model. The perspective adopted in developing the MT_CKD model has been to constrain the model so that it is consistent with quality analyses of spectral atmospheric and laboratory measurements of the foreign and self continuum. For field measurements, only cases for which the characterization of the atmospheric state has been highly scrutinized have been used. Continuum coefficients in spectral regions that have not been subject to compelling analyses are determined by a mathematical formulation of the spectral shape associated with each water vapour monomer line. This formulation, which is based on continuum values in spectral regions in which the coefficients are well constrained by measurements, is applied consistently to all water vapour monomer lines from the microwave to the visible. The results are summed-up (separately for the foreign and self) to obtain continuum coefficients from 0 to 20 000 cm(-1). For each water vapour line, the MT_CKD line shape formulation consists of two components: exponentially decaying far wings of the line plus a contribution from a water vapour molecule undergoing a weak interaction with a second molecule. In the MT_CKD model, the first component is the primary agent for the continuum between water vapour bands, while the second component is responsible for the majority of the continuum within water vapour bands. The MT_CKD model should be regarded as a semi-empirical model with strong constraints provided by the known physics. Keeping the MT_CKD continuum consistent with current observational studies necessitates periodic updates to the water vapour continuum coefficients. In addition to providing details on the MT_CKD line shape formulation, we describe the most recent update to the model, MT_CKD_2.5, which is based on an analysis of satellite- and ground-based observations from 2385 to 2600 cm(-1) (approx. 4 μm).
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Affiliation(s)
- Eli J Mlawer
- Atmospheric and Environmental Research, Lexington, MA, USA.
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Sams RL, Xantheas SS, Blake TA. Vapor Phase Infrared Spectroscopy and Ab Initio Fundamental Anharmonic Frequencies of Ammonia Borane. J Phys Chem A 2012; 116:3124-36. [DOI: 10.1021/jp2115753] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Robert L. Sams
- Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999,
MS K8-88, Richland, Washington 99352, United States
| | - Sotiris S. Xantheas
- Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999,
MS K8-88, Richland, Washington 99352, United States
| | - Thomas A. Blake
- Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999,
MS K8-88, Richland, Washington 99352, United States
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Paynter DJ, Ramaswamy V. An assessment of recent water vapor continuum measurements upon longwave and shortwave radiative transfer. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jd015505] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Gerecht E, Douglass KO, Plusquellic DF. Chirped-pulse terahertz spectroscopy for broadband trace gas sensing. OPTICS EXPRESS 2011; 19:8973-84. [PMID: 21643150 DOI: 10.1364/oe.19.008973] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We report the first demonstration of a broadband trace gas sensor based on chirp-pulse terahertz spectroscopy. The advent of newly developed solid state sources and sensitive heterodyne detectors for the terahertz frequency range have made it possible to generate and detect precise arbitrary waveforms at THz frequencies with ultra-low phase noise. In order to maximize sensitivity, the sample gas is first polarized using sub-μs chirped THz pulses and the free inductive decays (FIDs) are then detected using a heterodyne receiver. This approach allows for a rapid broadband multi-component sensing with low parts in 10(9) (ppb) sensitivities and spectral frequency accuracy of <20 kHz in real-time. Such a system can be configured into a portable, easy to use, and relatively inexpensive sensing platform.
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Affiliation(s)
- Eyal Gerecht
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
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Chen K, Yang H, Sun L, Jin G. Generalized method for calculating astigmatism of the unit-magnification multipass system. APPLIED OPTICS 2010; 49:1964-1971. [PMID: 20357882 DOI: 10.1364/ao.49.001964] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A generalized method to accurately calculate astigmatism of the unit-magnification multipass system (UMS) is proposed. A practical coaxial optical transmission model is developed for the UMS. Astigmatism analysis is then made convenient by a 4 by 4 general transfer matrix. Astigmatism correction is significantly promoted, and hence further improvement in imaging quality can be expected. Good agreement between numerical simulations and Zemax ray tracing results verifies the effectiveness of this method. The resulted RMS spot size of this method is only 25% to 64% of other previous methods based on the golden section search for minimum astigmatism in real design cases. This method is helpful for the optical design of the UMS.
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Affiliation(s)
- Kexin Chen
- State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, Beijing 100084, China.
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Paynter DJ, Ptashnik IV, Shine KP, Smith KM, McPheat R, Williams RG. Laboratory measurements of the water vapor continuum in the 1200–8000 cm−1region between 293 K and 351 K. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jd011355] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Rowe PM, Walden VP. Improved measurements of the foreign-broadened continuum of water vapor in the 6.3 microm band at -30 degrees C. APPLIED OPTICS 2009; 48:1358-1365. [PMID: 19252637 DOI: 10.1364/ao.48.001358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Atmospheric emission in the nu(2) band of water vapor by the foreign-broadened continuum (1300-2000 cm(-1)) is important for retrievals of upper tropospheric water vapor. Previous work reported continuum coefficients retrieved from two downwelling emission measurements made with the Polar Atmospheric Emitted Radiance Interferometer (PAERI) at temperatures characteristic of the upper troposphere (below -25 degrees C) at Dome C, Antarctica. These results are improved upon here using 19 different measurements. Improvements have been made to the PAERI radiance calibration, the radiance simulations, and the error analysis. Compared to the Mlawer, Tobin, Clough, Kneizys, Davies continuum, the retrieved continuum is found to be 20% to 50% lower from 1350 to 1490 cm(-1) and 0% to 20% higher from 1850 to 1980 cm(-1).
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Affiliation(s)
- Penny M Rowe
- Department of Geography, University of Idaho, Moscow, Idaho 83843, USA.
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Solodov A, Starikov V. Helium-induced halfwidths and line shifts of water vapor transitions of theν1+ν2andν2+ν3bands. Mol Phys 2009. [DOI: 10.1080/00268970802698655] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Serio C, Masiello G, Esposito F, Di Girolamo P, Di Iorio T, Palchetti L, Bianchini G, Muscari G, Pavese G, Rizzi R, Carli B, Cuomo V. Retrieval of foreign-broadened water vapor continuum coefficients from emitted spectral radiance in the H2O rotational band from 240 to 590 cm(-1). OPTICS EXPRESS 2008; 16:15816-15833. [PMID: 18825219 DOI: 10.1364/oe.16.015816] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The paper presents a novel methodology to retrieve the foreign-broadened water vapor continuum absorption coefficients in the spectral range 240 to 590 cm(-1) and is the first estimation of the continuum coefficient at wave numbers smaller than 400 cm(-1) under atmospheric conditions. The derivation has been accomplished by processing a suitable set of atmospheric emitted spectral radiance observations obtained during the March 2007 Alps campaign of the ECOWAR project (Earth Cooling by WAter vapor Radiation). It is shown that, in the range 450 to 600 cm(-1), our findings are in good agreement with the widely used Mlawer, Tobin-Clough, Kneizys-Davies (MT CKD) continuum. Below 450 cm(-1) however the MT CKD model overestimates the magnitude of the continuum coefficient.
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Affiliation(s)
- Carmine Serio
- Dip. Ingegeneria e Fisica dell'Ambiente, Universitá della Basilicata, Potenza, Italy.
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Ma Q, Tipping RH, Leforestier C. Temperature dependences of mechanisms responsible for the water-vapor continuum absorption. I. Far wings of allowed lines. J Chem Phys 2008; 128:124313. [PMID: 18376925 DOI: 10.1063/1.2839604] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
It is well known that the water-vapor continuum plays an important role in the radiative balance in the Earth's atmosphere. This was first discovered by Elsasser almost 70 years ago, and since that time there has been a large body of work, both experimental and theoretical, on this topic. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H(2)O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: Far wings of allowed transitions, water dimers, and collision-induced absorption. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the absorption. The first mechanism proposed was the accumulation of the far-wing absorption of the strong allowed transitions. Later, absorption by water dimers was proposed and this mechanism provides a qualitative explanation for the strong, negative T dependence. Recently, some atmospheric modelers have proposed that collision-induced absorption is one of the major contributors. However, based on improvements in the theoretical calculation of accurate far-wing line shapes, ab initio dimer calculations, and theoretical collision-induced absorptions, it is now generally accepted that the dominant mechanism for the absorption in the infrared (IR) windows is that due to the far wings. Whether this is true for other spectral regions is not presently established. Although all these three mechanisms have a negative T dependence, their T dependences will be characterized by individual features. To analyze the characteristics of the latter will enable one to assess their roles with more certainty. In this paper, we present a detailed study of the T dependence of the far-wing absorption mechanism. We will then compare our theoretical calculations with the most recent and accurate experimental data in the IR windows. The results of our calculations are found to agree very well with measurements in the 800-1200 cm(-1) region. We conclude from this work that the T dependence in the IR window region predicted by the far-wing theory is negative and moderately strong. Its pattern is not simple and it could vary significantly as the frequency of interest varies.
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Affiliation(s)
- Q Ma
- NASA/Goddard Institute for Space Studies and Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, New York 10025, USA.
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Rowe PM, Walden VP, Warren SG. Measurements of the foreign-broadened continuum of water vapor in the 6.3 microm band at -30 degrees C. APPLIED OPTICS 2006; 45:4366-82. [PMID: 16778946 DOI: 10.1364/ao.45.004366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The foreign-broadened continuum of water vapor in the nu2 band (5-7.7 microm, 1300-2000 cm(-1)) is important for satellite-based retrievals of water vapor in the upper troposphere, where temperatures are below -25 degrees C. Continuum coefficients have previously been measured mostly at or above +23 degrees C. We present continuum coefficients in the nu(2) band retrieved from measurements made in Antarctica at temperatures near -30 degrees C: atmospheric transmission at South Pole Station and atmospheric emission at Dome C. The continuum coefficients derived from these measurements are generally in agreement with the widely used Mlawer, Tobin-Clough, Kneizys, Davies continuum. Differences are at most 30%, corresponding to a 6% relative error in retrieved upper-tropospheric humidity.
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Affiliation(s)
- Penny M Rowe
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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Sierk B. Field measurements of water vapor continuum absorption in the visible and near-infrared. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003jd003586] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Maté B, Lugez CL, Solodov AM, Fraser GT, Lafferty WJ. Investigation of the collision-induced absorption by O2near 6.4 μm in pure O2and O2/N2mixtures. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/2000jd900295] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Godon M, Bauer A, Gamache RR. The Continuum of Water Vapor Mixed with Methane: Absolute Absorption at 239 GHz and Linewidth Calculations. JOURNAL OF MOLECULAR SPECTROSCOPY 2000; 202:293-302. [PMID: 10877960 DOI: 10.1006/jmsp.2000.8143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In the aim of achieving a better understanding of the molecular mechanisms involved in the absorption continuum of the water-vapor rotational spectrum, various H(2)O-X mixtures are investigated in an atmospheric window in the mmw range. In the present study, the X mixing gas is methane. Absolute absorption rates have been measured at 239 GHz. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with models using conventional line profiles. As these models require the knowledge of the collisional half-widths of H(2)O broadened by CH(4), theoretical calculations using the complex Robert-Bonamy formalism have been carried out. A "continuum effect" is observed when comparing the experimental absorption with the models, as well as for the magnitude of the absorption discrepancy and for the strong temperature dependence of this absorption. The effect is compared for various X mixing gases to the collisional broadening efficiency in the impact approximation. Copyright 2000 Academic Press.
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Affiliation(s)
- M Godon
- Laboratoire de Physique des Lasers, Atomes et Molécules, UMR CNRS, Université des Sciences et Technologies de Lille, CERLA, Villeneuve d'Ascq Cedex, 59655, France
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Iacono MJ, Mlawer EJ, Clough SA, Morcrette JJ. Impact of an improved longwave radiation model, RRTM, on the energy budget and thermodynamic properties of the NCAR community climate model, CCM3. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/2000jd900091] [Citation(s) in RCA: 307] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Maté B, Fraser GT, Lafferty WJ. Intensity of the Simultaneous Vibrational Absorption CO(2) (v(3) = 1) + N(2) (v = 1) <-- CO(2) (v(3) = 0) + N(2) (v = 0) at 4680 cm(-1). JOURNAL OF MOLECULAR SPECTROSCOPY 2000; 201:175-177. [PMID: 10753625 DOI: 10.1006/jmsp.2000.8074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- B Maté
- Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899-8441
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Maté B, Lugez C, Fraser GT, Lafferty WJ. Absolute intensities for the O21.27 μm continuum absorption. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1999jd900824] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Tobin DC, Best FA, Brown PD, Clough SA, Dedecker RG, Ellingson RG, Garcia RK, Howell HB, Knuteson RO, Mlawer EJ, Revercomb HE, Short JF, van Delst PFW, Walden VP. Downwelling spectral radiance observations at the SHEBA ice station: Water vapor continuum measurements from 17 to 26μm. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998jd200057] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Lafferty WJ, Solodov AM, Lugez CL, Fraser GT. Rotational Line Strengths and Self-Pressure-Broadening Coefficients for the 1.27-microm, a (1)D(g)-X (3)?(g)(-), v = 0-0 Band of O(2). APPLIED OPTICS 1998; 37:2264-2270. [PMID: 18273151 DOI: 10.1364/ao.37.002264] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We measured at 296 K the rotational line strengths and pressure-broadening coefficients for the 1.27-mum, a (1)D(g)-X (3)?(g)(-), v = 0-0 band of O(2) with a Fourier transform infrared spectrometer using an optical path length of 84 m, a spectral resolution of 0.01 cm(-1), and sample pressures between 13 and 104 kPa. The integrated band strength is 7.79(17) x 10(-6) m(-2) Pa(-1) [7.89(17) x 10(-5) cm(-2) atm(-1)], and the Einstein Acoefficient for spontaneous emission is 2.237(51) x 10(-4) s(-1), which corresponds to an upper-state1/e lifetime of 1.24(3) h. The pressure-broadening coefficients decrease with increasing N and range from 19 to 38 MHz/kPa (FWHM). The mean value for the transitions studied is 30.3(21) MHz/kPa [0.1024(71) cm(-1)/atm] (FWHM). The Einstein A coefficient determined here is in good agreement with the widely accepted value of 2.58 x 10(-4) s(-1) initially obtained by Badgeret al. [J. Chem. Phys. 43, 4345 (1965)] more than 30 years ago. The standard uncertainties given above are one standard deviation.
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Lafferty WJ, Solodov AM, Weber A, Olson WB, Hartmann JM. Infrared collision-induced absorption by N(2) near 4.3 μm for atmospheric applications: measurements and empirical modeling. APPLIED OPTICS 1996; 35:5911-5917. [PMID: 21127602 DOI: 10.1364/ao.35.005911] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Accurate measurements of collision-induced absorption by pure nitrogen in the fundamental band near 4.3 μm have been made in the 0-10 atm and 230-300 K pressure and temperature ranges, respectively. A Fourier-transform spectrometer was used with a resolution of 0.5 cm(-1). The current measurements, which agree well with previous ones but are more precise, reveal that weak features are superimposed on the broad N(2) continuum. These features have negligible temperature dependence, and their origin is not clear at the present time. Available experimental data in the 190-300 K temperature range have been used to build a simple empirical model that is suitable for use to compute atmospheric N(2) absorption. Tests indicate that this model is accurate unlike the estimates produced by widely used atmospheric transmission codes.
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