| 1. |
- Axner, Ove, et al.
(författare)
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A general non-complex analytical expression for the nth Fourier component of a wavelength-modulated Lorentzian lineshape function
- 2001
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 68:3, s. 299-317
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Tidskriftsartikel (refereegranskat)abstract
- A general, analytical expression for the nth Fourier component of a wavelength-modulated Lorentzian lineshape function in terms of a normalized detuning and a normalized modulation amplitude is derived. The expression is cast in a purely real form and is therefore easier to use than the normally used expression, which is given in terms of various combinations (sums, square roots, and powers) of complex expressions and their complex conjugates. Analytical expressions for the nine first Fourier components (n = 0,...,8), clearly showing their dependence on normalized detuning and modulation amplitude, are explicitly given. Simplified expressions for the even harmonics of the Fourier components on resonance, at which they take their maximum value, solely given in terms of the normalized modulation amplitude, are also explicitly given. It is shown that previously published, numerically calculated conditions for maximization of higher-order Fourier components are incorrect. The normalized modulation amplitudes that maximize the four lowest even harmonics of the Fourier components, i.e. for n = 2, 4, 6, and 8, are 2.20, 4.12, 6.08, and 8.06, respectively.
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| 2. |
- Eriksson, Patrick, et al.
(författare)
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A Hotelling transformation approach for rapid inversion of atmospheric spectra
- 2002
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 73:6, s. 529-543
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric observations from space often result in spectral data of large dimensions. To allow an optimal inversion of the observed spectra it can be necessary to map the data into a space of smaller dimension. Here several data reduction techniques based on eigenvector expansions of the spectral space are compared. The comparison is done by inverting simulated observations from a microwave limb sounder, the Odin-SMR. For the examples tested, reductions exceeding two orders of magnitude with no negative influence on the retrieval performance are demonstrated. The techniques compared include a novel method developed especially for atmospheric inversions, based on the weighting functions of the variables to be retrieved. The new method shows an excellent performance in practical tests and is both computationally more effective and more flexible than the standard Hotelling transformation.
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| 3. |
- Kuhn, Thomas, 1970-, et al.
(författare)
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Water vapor continuum: absorption measurements at 350 Ghz and model calculations
- 2002
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 74:5, s. 545-562
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Tidskriftsartikel (refereegranskat)abstract
- Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the laboratory at 350 GHz. The dependence on pressure and temperature has been obtained. Additionally, a water vapor continuum parameter estimation, taking even the previous laboratory measurements from 150 to 350 GHz into account, is performed.
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| 4. |
- López-Puertas, M., et al.
(författare)
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Non-local thermodynamic equilibrium limb radiances for the mipas instrument on Envisat-1
- 1998
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 59:3-5, s. 377-403
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation of the effects that the assumption of local thermodynamic equilibrium (LTE) has on the retrieval of pressure, temperature and the five primary target gases (O3, H2O, CH4, N2O, and HNO3) from spectra to be taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the Envisat-1 platform has been conducted. For doing so, non-LTE and LTE limb radiances in the spectral range of 680–2275 cm−1 (4.15–14.6 μm) with a resolution of 0.05 cm−1 at tangent heights from 10 to 70 km have been computed. These calculations included the most updated non-LTE populations of a large number of vibrational levels of the CO2, O3, H2O, CH4, N2O and HNO3 molecules which cause the most prominent atmospheric infrared emissions. A discussion of the most important non-LTE effects on the limb radiances as well as on the retrievals of pressure-temperature and volume mixing ratios of O3, H2O, CH4, N2O, and HNO3 is presented, together with the most important non-LTE issues that could be studied with the future coming of MIPAS data.
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| 5. |
- Manuilova, R.O., et al.
(författare)
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Modelling of non-LTE limb spectra of i.r. ozone bands for the MIPAS space experiment
- 1998
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 59:3-5, s. 405-422
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Tidskriftsartikel (refereegranskat)abstract
- A new model for calculating the populations of the ozone vibrational states under non-LTE (Local Thermodynamic Equilibrium) conditions is presented. In the model, 23 vibrational levels of the O3 molecule, as well as three vibrational levels of the O2 molecule and two vibrational levels of the N2 molecule, are considered. The radiative transfer at the break-down of LTE was treated explicitly for 150 000 ro-vibrational transitions. The populations obtained were used to calculate limb radiances in various spectral regions of the 4.8 and 9.6 μm bands. Test retrievals of O3 vertical volume mixing ratio (VMR) profiles with a radiance model disregarding non-LTE were performed in order to assess the potential impact of non-LTE effects on the retrieval of the O3 abundances from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) measurements.
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| 6. |
- Sikström, C.M., et al.
(författare)
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Uncertainty of oscillator strengths derived from lifetimes and branching fractions
- 2002
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 74:3, s. 355-368
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Tidskriftsartikel (refereegranskat)abstract
- A widely used method for determination of transition probabilities and oscillator strengths is based on measurements of branching fractions and radiative lifetimes. In the present work the different sources of uncertainty in branching fraction measurements using Fourier transform spectroscopy and lifetime measurements using laser induced fluorescence are discussed. A detailed description is presented of how the uncertainties should be combined to provide a well-defined uncertainty of the derived quantity. Finally, an example shows how the individual uncertainties can be presented in an “uncertainty budget”.
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| 7. |
- Sreerekha, T. R., et al.
(författare)
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A simple new radiative transfer model for simulating the effect of cirrus clouds in the microwave spectral region
- 2002
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 75:5, s. 611-624
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Tidskriftsartikel (refereegranskat)abstract
- The upwelling atmospheric radiation in the millimeter wave spectral range is influenced by the presence of cirrus clouds. A plane parallel radiative transfer model which can take into account the effect of multiple scattering by ice particles in the cirrus has been developed and is used to simulate the brightness temperatures as they would be measured by a satellite instrument. The model uses an iterative procedure to solve the radiative transfer equation. The formulation of the model is such that it can easily be adapted to treat the full specific intensity vector instead of just the scalar total intensity. A convergence test for the model is explained and two cirrus cloud scenarios are simulated. The results illustrate the linearity of microwave radiative transfer for not too strong cirrus clouds in this frequency region
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| 8. |
- Ashraf, Shakeel, 1984-, et al.
(författare)
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Determination of complex refractive index of SU-8 by Kramers-Kronig dispersion relation method at the wavelength range 2.5 – 22.0 μm
- 2019
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 224, s. 309-311
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Tidskriftsartikel (refereegranskat)abstract
- Accurate determination of the complex refractive index of SU-8 epoxy has significant for the wide variety of applications in optical sensor technology at IR range. The complex refractive index of SU-8 is determined by recording the transmission of light spectra for the wavelength range of 2.5 – 22.0 μm. The data analysis is based on the Kramers-Kronig dispersion relation method. The method has several merits, such as ease of operation, non-contact technique, measurement accuracy, and rapid measurement. The present method is not restricted to the case of SU-8 but it is also proposed to be applicable across a broad range of applications, such as assessment of the optical properties of paints and biomedical samples.
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| 9. |
- Atalay, B., et al.
(författare)
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Extended relativistic multiconfiguration calculations of energy levels and transition properties in singly ionized tin
- 2023
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 294
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Tidskriftsartikel (refereegranskat)abstract
- Multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations are performed for 22 states in singly ionized tin (Sn II) belonging to the 5s2ns (n=6,7), 5s2nd (n=5,6), 5s5p2 even parity configurations and the 5s2np (n=5,6,7), 5s24f odd parity configurations. Valence-valence and core-valence correlation effects are taken into account through configuration state function (CSF) expansions. Complete and consistent data sets of level energies, wavelengths, oscillator strengths, lifetimes and transition rates among all these states are given. The results are compared with existing theoretical and experimental results. There is an excellent agreement for calculated excitation energies with experimental data from the NIST database. Lifetimes and transition rates are also in agreement with the results from previous calculations and available measurements for most of the transitions.
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| 10. |
- Buehler, Stefan A., et al.
(författare)
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ARTS, the atmospheric radiative transfer simulator
- 2005
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 91:1, s. 65-93
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Tidskriftsartikel (refereegranskat)abstract
- RTS is a modular program that simulates atmospheric radiative transfer. The paper describes ARTS version 1.0, which is applicable in the absence of scattering. An overview over all major parts of the model is given: calculation of absorption coefficients, the radiative transfer itself, and the calculation of Jacobians. ARTS can be freely used under a GNU general public license. Unique features of the program are its scalability and modularity, the ability to work with different sources of spectroscopic parameters, the availability of several self-consistent water continuum and line absorption models, and the analytical calculation of Jacobians.
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| 11. |
- Buehler, Stefan A., et al.
(författare)
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Efficient radiative transfer simulations for a broadband infrared radiometer—Combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing
- 2010
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 111:4, s. 602-615
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to efficiently simulate the measurements of a broadband infrared instrument. The High Resolution Infrared Radiation Sounder (HIRS) instrument is used as example to illustrate the method. The method uses two basic ideas. Firstly, the channel radiance can be approximated by a weighted mean of the radiance at some representative frequencies, where the weights can be determined by linear regression. Secondly, a near-optimal set of representative frequencies can be found by simulated annealing.The paper does not only describe and analyze the method, it also describes how the method was used to derive optimized frequency grids for the HIRS instruments on the satellites TIROS N, NOAA 6-19, and Metop A. The grids and weights, as well as the optimization algorithm itself are openly available under a GNU public license.
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| 12. |
- Buehler, Stefan, et al.
(författare)
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Absorption lookup tables in the radiative transfer model ARTS
- 2011
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 112:10, s. 1559-1567
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Tidskriftsartikel (refereegranskat)abstract
- We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.
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| 13. |
- Buehler, Stefan, et al.
(författare)
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Recent developments in the line-by-line modeling of outgoing longwave radiation
- 2006
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 98:3, s. 446-457
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Tidskriftsartikel (refereegranskat)abstract
- High frequency resolution radiative transfer model calculations with the Atmospheric Radiative Transfer Simulator (ARTS) were used to simulate the clear-sky outgoing longwave radiative flux (OLR) at the top of the atmosphere. Compared to earlier calculations by Clough and coworkers the model used a spherical atmosphere instead of a plane parallel atmosphere, updated spectroscopic parameters from HITRAN, and updated continuum parameterizations from Mlawer and coworkers. These modifications lead to a reduction in simulated OLR by approximately 4.1%, the largest part, approximately 2.5%, being due to the absence of the plane parallel approximation. As a simple application of the new model, the sensitivity of OLR to changes in humidity, carbon dioxide concentration, and temperature were investigated for different cloud-free atmospheric scenarios. It was found that for the tropical scenario a 20% change in humidity has a larger impact than a doubling of the carbon dioxide concentration. The sensitive altitude region for temperature and humidity changes is the entire free troposphere, including the upper troposphere where humidity data quality is poor.
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| 14. |
- Chen, Zhan-Bin, et al.
(författare)
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Theoretical energies, transition rates, lifetimes, hyperfine interaction constants and Lande g(J-)factors for the Se XXVII spectrum of fusion interest
- 2018
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 206, s. 213-232
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Tidskriftsartikel (refereegranskat)abstract
- An extensive set of level energies, wavelengths, line strengths, oscillator strengths, lifetimes, hyperfine structures, Lande g(J)-factors, electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transition rates among the lowest 318 states arising from the 2s(2)2p(4), 2s2(p)5, 2p(6), 2s(2)2p(3)3l (l = 0, 1, 2), 2s2p(4)31 (l = 0, 1, 2), 2p(5)3l (l = 0, 1, 2), and 2s(2)2p(3)4l (l = 0, 1, 2, 3) configurations has been obtained for Se XXVII. These new data, calculated within the frameworks of the multi-configuration Dirac-Hartree-Fock method and the second-order many-body perturbation theory, fill in the gap existing in the atomic data needed for the diagnostic processes of tokamak plasmas. Using two methods allowed us to make an intercomparison and to estimate the uncertainties on the obtained data. The results arising in the two sets of calculations are quite close, suggesting that there is a high degree of convergence achieved in our work. i.e., our two sets of energies agree to better than 0.02%, and the lifetimes mostly agree to within 2%. Comparison is also made with the limited number of experimental data and previous computations to assess the accuracy of our calculations. (C) 2017 Elsevier Ltd. All rights reserved.
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| 15. |
- Dubernet, M. L., et al.
(författare)
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Virtual atomic and molecular data centre
- 2010
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 111:15, s. 2151-2159
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Tidskriftsartikel (refereegranskat)abstract
- The Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu) is a European Union funded collaboration between groups involved in the generation, evaluation, and use of atomic and molecular data. VAMDC aims to build a secure, documented, flexible and interoperable e-science environment-based interface to existing atomic and molecular data. The project will cover establishing the core consortium, the development and deployment of the infrastructure and the development of interfaces to the existing atomic and molecular databases. It will also provide a forum for training potential users and dissemination of expertise worldwide. This review describes the scope of the VAMDC project; it provides a survey of the atomic and molecular data sets that will be included plus a discussion of how they will be integrated. Some applications of these data are also discussed.
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| 16. |
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| 17. |
- Eriksson, Patrick, 1964, et al.
(författare)
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ARTS, the atmospheric radiative transfer simulator, Version 2
- 2011
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 112:10, s. 1551-1558
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Tidskriftsartikel (refereegranskat)abstract
- The second version of the atmospheric radiative transfer simulator. ARTS, is introduced. This is a general software package for long wavelength radiative transfer simulations, with a focus on passive microwave observations. The core part provides a workspace environment, in line with script languages. New for this version is an agenda mechanism that gives a high degree of modularity. The framework is intended to be as general as possible: the polarisation state can be fully described, the model atmosphere can be one- (1D), two- (2D) or three-dimensional (3D), a full description of geoid and surface is possible, observation geometries from the ground, from satellite, and from aeroplane or balloon are handled, and surface reflection can be treated in simple or complex manners. Remote sensing applications are supported by a comprehensive and efficient treatment of sensor characteristics. jacobians can be calculated for the most important atmospheric variables in non-scattering conditions. Finally, the most prominent feature is the rigorous treatment of scattering that has been implemented in two modules: a discrete ordinate iterative approach mainly used for 1D atmospheres, and a Monte Carlo approach which is the preferred algorithm for 3D atmospheres. ARTS is freely available, and maintained as an open-source project.
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| 18. |
- Eriksson, Patrick, et al.
(författare)
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Qpack : a general tool for instrument simulation and retrieval work
- 2005
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 91:1, s. 47-64
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Tidskriftsartikel (refereegranskat)abstract
- Remote sensing requires a complete observation system, consisting of the instrument, a forward model and a retrieval environment. This paper presents a software tool to complement atmospheric sensors, with focus on passive instruments operating in the mm and sub-mm wavelength regions. The tool is of general character and offers a complete, flexible and fast calculation environment, demonstrated in both preparatory instrument studies and operational inversions. Its features include a rapid approach for modelling of sensor characteristics, several types of data reduction, simple definition of covariance matrices, a large number of retrieval and error quantities, inversion characterisation and random realisation of measurements. The software is freely available for scientific use.
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| 19. |
- Ershov, A. E., et al.
(författare)
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Thermal limiting effects in optical plasmonic waveguides
- 2017
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0022-4073 .- 1879-1352. ; 191, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- We have studied thermal effects occurring during excitation of optical plasmonic waveguide (OPW) in the form of linear chain of spherical Ag nanoparticles by pulsed laser radiation. It was shown that heating and subsequent melting of the first irradiated particle in a chain can significantly deteriorate the transmission efficiency of OPW that is the crucial and limiting factor and continuous operation of OPW requires cooling devices. This effect is caused by suppression of particle's surface plasmon resonance due to reaching the melting point temperature. We have determined optimal excitation parameters which do not significantly affect the transmission efficiency of OPW.
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| 20. |
- Fakhardji, Wissam, 1990-, et al.
(författare)
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Direct method for MD simulations of collision-induced absorption : application to an Ar–Xe gas mixture
- 2021
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- With the reformulation of the classical equations of collision-induced absorption, we present a method to perform the direct computation of the spectral density function. This way the absorption coefficient can be computed from classical molecular dynamics (MD) without the computationally demanding evaluation of the dipole autocorrelation function. In addition, we have developed an algorithm to extract the bound-to-bound dimer contribution to the MD simulated absorption. The method has been tested on the Ar–Xe rare gas system. Comparisons with quantum mechanical (QM) and conventional MD methods validate the approach. The obtained MD bound-to-bound spectra generally agree in shape and magnitude with QM results, including features stemming from rotations and vibrations of the Ar–Xe dimer.
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| 21. |
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| 22. |
- Foltynowicz, Aleksandra, et al.
(författare)
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Wavelength modulation absorption spectrometry from optically pumped collision broadened atoms and molecules
- 2007
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - Oxford : Pergamon Press. - 0022-4073 .- 1879-1352. ; 108:2, s. 220-238
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical investigation of the influence of optical pumping on wavelength modulation absorption spectrometry (WMAS) signals from collision broadened atoms and molecules is presented. General expressions for the nf-WMAS signal from atomic and molecular systems, modeled as three-level systems that can accommodate both optical saturation and optical pumping, are derived by the use of a previously developed Fourier series-based formalism in combination with rate equations solved under steady-state conditions. The expressions are similar to those describing the nf-WMAS signal from two-level systems that can accommodate optical saturation [Schmidt FM, Foltynowicz A, Gustafsson J, Axner O, WMAS from optically saturated collision-broadened transitions. JQSRT 2005;94:225–54], the difference being the value of the saturation flux, wherefore the general parametric dependence of WMAS signals from optically pumped systems is the same as that from optically saturated systems. The additional effect of optical pumping on the WMAS signal is investigated for three typical cases: molecules or atoms in an ordinary atmosphere, atoms in an inert atmosphere, and atoms or molecules possessing metastable states. The possibility to describe any of these systems with a two-level model is investigated.
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| 23. |
- Gasteiger, J., et al.
(författare)
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Representative wavelengths absorption parameterization applied to satellite channels and spectral bands
- 2014
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 148, s. 99-115
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Tidskriftsartikel (refereegranskat)abstract
- Accurate modeling of wavelength-integrated radiative quantities, e.g. integrated over a spectral band or an instrument channel response function, requires computations for a large number of wavelengths if the radiation is affected by gas absorption which typically comprises a complex line structure. In order to increase computational speed of modeling radiation in the Earth׳s atmosphere, we parameterized wavelength-integrals as weighted means over representative wavelengths. We parameterized spectral bands of different widths (1 cm−1, 5 cm−1, and 15 cm−1) in the solar and thermal spectral range, as well as a number of instrument channels on the ADEOS, ALOS, EarthCARE, Envisat, ERS, Landsat, MSG, PARASOL, Proba, Sentinel, Seosat, and SPOT satellites. A root mean square relative deviation lower than 1% from a “training data set” was selected as the accuracy threshold for the parameterization of each band and channel. The training data set included high spectral resolution calculations of radiances at the top of atmosphere for a set of highly variable atmospheric states including clouds and aerosols. The gas absorption was calculated from the HITRAN 2004 spectroscopic data set and state-of-the-art continuum models using the ARTS radiative transfer model. Three representative wavelengths were required on average to fulfill the accuracy threshold. We implemented the parameterized spectral bands and satellite channels in the uvspec radiative transfer model which is part of the libRadtran software package. The parameterization data files, including the representative wavelengths and weights as well as lookup tables of absorption cross sections of various gases, are provided at the libRadtran webpage.In the paper we describe the parameterization approach and its application. We validate the approach by comparing modeling results of parameterized bands and channels with results from high spectral resolution calculations for atmospheric states that were not part of the training data set. Irradiances are not only compared at the top of atmosphere but also at the surface for which this parameterization approach was not optimized. It is found that the parameterized bands and channels provide a good compromise between computation time requirements and uncertainty for typical radiative transfer problems. In particular for satellite radiometer simulations the computation time requirement and the parameterization uncertainty is low. Band-integrated irradiances at any level as well as heating and cooling rates below 20 km can also be modeled with low uncertainty.
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| 24. |
- Germann, Matthias, et al.
(författare)
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A methane line list with sub-MHz accuracy in the 1250 to 1380 cm−1 range from optical frequency comb Fourier transform spectroscopy
- 2022
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 288
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Tidskriftsartikel (refereegranskat)abstract
- We use a Fourier transform spectrometer based on a difference frequency generation optical frequency comb to measure high-resolution, low-pressure, room-temperature spectra of methane in the 1250 – 1380-cm−1 range. From these spectra, we retrieve line positions and intensities of 678 lines of two isotopologues: 157 lines from the 12CH4 ν4 fundamental band, 131 lines from the 13CH4 ν4 fundamental band, as well as 390 lines from two 12CH4 hot bands, ν2 + ν4 – ν2 and 2ν4 – ν4. For another 165 lines from the 12CH4 ν4 fundamental band we retrieve line positions only. The uncertainties of the line positions range from 0.19 to 2.3 MHz, and their median value is reduced by a factor of 18 and 59 compared to the previously available data for the 12CH4 fundamental and hot bands, respectively, obtained from conventional FTIR absorption measurements. The new line positions are included in the global models of the spectrum of both methane isotopologues, and the fit residuals are reduced by a factor of 8 compared to previous absorption data, and 20 compared to emission data. The experimental line intensities have relative uncertainties in the range of 1.5 – 7.7%, similar to those in the previously available data; 235 new 12CH4 line intensities are included in the global model.
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| 25. |
- Germann, Matthias, et al.
(författare)
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Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range : experimental line list and improved MARVEL analysis
- 2024
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- We use optical frequency comb Fourier transform spectroscopy to record high-resolution, low-pressure, room-temperature spectra of formaldehyde (H212C16O) in the range of 1250 to 1390 cm−1. Through line-by-line fitting, we retrieve line positions and intensities of 747 rovibrational transitions: 558 from the ν6 band, 129 from the ν4 band, and 14 from the ν3 band, as well as 46 from four different hot bands. We incorporate the accurate and precise line positions (0.4 MHz median uncertainty) into the MARVEL (measured active vibration-rotation energy levels) analysis of the H2CO spectrum. This increases the number of MARVEL-predicted energy levels by 82 and of rovibrational transitions by 5382, and substantially reduces uncertainties of MARVEL-derived H2CO energy levels over a large range: from pure rotational levels below 200 cm−1 up to multiply excited vibrational levels at 6000 cm−1. This work is an important step toward filling the gaps in formaldehyde data in the HITRAN database.
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