5 results on '"Mantz, A.W."'
Search Results
2. Assignment and modelling of 12CH4 spectra in the 5550–5695, 5718–5725 and 5792–5814 cm−1 regions.
- Author
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Nikitin, A.V., Thomas, X., Daumont, L., Rey, M., Sung, K., Toon, G.C., Smith, M.A.H., Mantz, A.W., Protasevich, A.E., Tashkun, S.A., and Tyuterev, Vl.G.
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METHANE spectra , *FOURIER transform spectrometers , *CURVE fitting , *LEAST squares , *STANDARD deviations , *HAMILTONIAN systems - Abstract
Highlights • 5819 line positions and intensities were retrieved from measured spectra in the 5550- 5825 cm−1 region. • More than 2800 new assignments were made in the region. • More than 3445 experimental line positions were modeled to 0.0024 cm−1. Abstract A new study of 12CH 4 line positions and intensities was performed for the Tetradecad regions 5550,000–5695.250, 5718.8–5724.250 and 5792.36–5814.290 cm−1 using long path (202 m, 602 m, 1604 m and 1804 m) spectra of normal samples of CH 4 at different pressures recorded with a Fourier transform spectrometer in Reims, France. Line positions and intensities were retrieved by least squares curve-fitting procedures and analyzed using the effective Hamiltonian and the effective dipole moment expressed in terms of irreducible tensor operators adapted to spherical top molecules. An 80 K spectrum recorded in Jet Propulsion Laboratory (JPL), Pasadena, of enriched 12CH 4 was used for low-J line positions. Another 80 K spectrum of enriched 13CH 4 from JPL was used to discern the isotopic lines. A new measured linelist contains positions and intensities for 5819 features. Quantum assignments were made for more than 3400 transitions, which represent ∼95% of the integrated line intensity observed in this region. All assigned 3445 line positions were fitted with RMS standard deviations of 0.0024 cm−1. The sum of observed intensities between 5550 and 5695 cm−1 fell within 2% of the predicted value from ab initio variational calculations reported in the TheoReTS database (http://theorets.univ-reims.fr ; http://theorets.tsu.ru). [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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3. Measurements and modeling of cold 13CH4 spectra in the 3750–4700 cm−1 region.
- Author
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Brown, L.R., Nikitin, A.V., Sung, K., Rey, M., Tashkun, S.A., Tyuterev, Vl.G., Crawford, T.J., Smith, M.A.H., and Mantz, A.W.
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COLD (Temperature) , *METHANE analysis , *TEMPERATURE effect , *LEAST squares , *HAMILTONIAN systems , *OPERATOR theory - Abstract
A new study of 13 CH 4 line intensities and positions was performed in the Octad region between 3750 and 4700 cm −1 . Using 13 C-enriched samples, spectra were recorded with both the McMath–Pierce FTS at Kitt Peak Observatory in Arizona and the Bruker IFS-125HR at JPL. Sample temperatures ranged between 80 and 296 K. Line positions and intensities of ~15,000 features were retrieved at different temperatures by non-linear least squares curve-fitting procedures. Intensities were used to estimate the lower state energies for 60% of the features in order to determine quantum assignments up to J =10. A preliminary analysis was performed using the effective Hamiltonian and the effective dipole transition moment expressed in terms of irreducible tensor operators adapted to spherical top molecules. Selected assignments were made up to J =10 for all 24 sub-vibrational states of the Octad; these were modeled for 4752 experimental line positions and 3301 selected line intensities fitted with RMS standard deviations of 0.004 cm −1 and 6.9%, respectively. Integrated intensities of the eight Octad bands are compared to ab initio variational calculations. A prediction of the 13 CH 4 is given, but further analysis to improve the calculation will be reported in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
4. Preliminary modeling of CH3D from 4000 to 4550cm−1
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Nikitin, A.V., Brown, L.R., Sung, K., Rey, M., Tyuterev, Vl.G., Smith, M.A.H., and Mantz, A.W.
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FOURIER transform infrared spectroscopy , *METHANE , *LEAST squares , *HAMILTONIAN systems , *QUANTUM theory , *TEMPERATURE effect - Abstract
Abstract: A new study of 12CH3D line positions and intensities was performed for the upper portion of the Enneadecad polyad between 4000 and 4550cm−1. For this, FTIR spectra were recorded with D-enriched methane samples (at 80K with a Bruker 125 IFS at 0.005cm−1 resolution and at 291K with the McMath-Pierce FTS at 0.011cm−1 resolution, respectively). Line positions and intensities were retrieved by least square curve-fitting procedures and analyzed using the effective Hamiltonian and the effective dipole moment expressed in terms of irreducible tensor operators adapted to symmetric top molecules. Initially, only the cold spectrum was used to identify quantum assignments and predict 12CH3D relative intensities in this region. To assign higher quanta up to J equal 14, additional line positions and intensities were obtained from two room temperature spectra. In the final stage, measured intensities from both the cold and the room temperature data were normalized to corresponding values at 296K and then averaged. Combining the two temperature datasets confirmed the assumed quantum assignments and also demonstrated the relative accuracies to be better than ±0.0002cm−1 for line positions and at least ±6% for intensities so that ∼1160 features were selected. Including additional assignments from the room temperature spectra alone permitted 1362 line intensities of 11 bands (involving 23 vibrational symmetry components) to be reproduced with an RMS of 9%. Over 4085 selected positions for 12 bands were modeled to 0.008cm−1. Nevertheless a number of known assignments could not be modeled to within our experimental precisions. More work is needed to obtain a complete characterization of this complex polyad. [Copyright &y& Elsevier]
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- 2013
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5. Spectral line parameters including temperature dependences of self- and air-broadening in the 2←0 band of CO at 2.3μm
- Author
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Malathy Devi, V., Chris Benner, D., Smith, M.A.H., Mantz, A.W., Sung, K., Brown, L.R., and Predoi-Cross, A.
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TEMPERATURE effect , *CARBON monoxide , *PRESSURE , *SIGNAL-to-noise ratio , *FOURIER transform spectrometers , *LEAST squares - Abstract
Abstract: Temperature dependences of pressure-broadened half-width and pressure-induced shift coefficients along with accurate positions and intensities have been determined for transitions in the 2←0 band of 12C16O from analyzing high-resolution and high signal-to-noise spectra recorded with two different Fourier transform spectrometers. A total of 28 spectra, 16 self-broadened and 12 air-broadened, recorded using high-purity (≥99.5% 12C-enriched) CO samples and CO diluted with dry air (research grade) at different temperatures and pressures, were analyzed simultaneously to maximize the accuracy of the retrieved parameters. The sample temperatures ranged from 150 to 298K and the total pressures varied between 5 and 700Torr. A multispectrum nonlinear least squares spectrum fitting technique was used to adjust the rovibrational constants (G, B, D, etc.) and intensity parameters (including Herman–Wallis coefficients), rather than determining individual line positions and intensities. Self- and air-broadened Lorentz half-width coefficients, their temperature dependence exponents, self- and air-pressure-induced shift coefficients, their temperature dependences, self- and air- line mixing coefficients, their temperature dependences and speed dependence have been retrieved from the analysis. Speed-dependent line shapes with line mixing employing off-diagonal relaxation matrix element formalism were needed to minimize the fit residuals. This study presents a precise and complete set of spectral line parameters that consistently reproduce the spectrum of carbon monoxide over terrestrial atmospheric conditions. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
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