Line Positions and Intensities in the 2ν2/ν4 Vibrational System of 14NH3 near 5–7 μm

Cottaz, C.; Kleiner, Isabelle; Tarrago, G.; Brown, L.R.; Margolis, J. S.; Poynter, R. L.; Pickett, H. M.; Fouchet, Thierry; Drossart, P.; Lellouch, E.

doi:10.1006/jmsp.2000.8182

Cited by 65 publications

(40 citation statements)

References 37 publications

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“…To solve this problem, we included 475 combination differences derived from the transitions of the 4 and 2 2 fundamental bands that connect different K's. 7 The correlation was reduced once the combination differences were included and transitions with J Ն 30 were then assigned. The signal-to-noise ratio of the assigned J = 35 transitions is ϳ3 and we assigned all the observed high-J transitions from our discharge Fourier transform spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…The previous attempt at a global analysis of the 2 =2 and 4 = 1 states ignored the available 2 2 − 4 microwave data and achieved a standard deviation of 0.003 cm −1 , 7,8 which is an order of magnitude larger than experimental accuracy. The difficulties in assignments and analyses only worsen at higher levels of excitation where the interactions of more vibrational modes dominate the spectrum.…”

Section: Introductionmentioning

confidence: 96%

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Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

Pearson

Drouin

et al. 2010

The Journal of Chemical Physics

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Complete and reliable knowledge of the ammonia spectrum is needed to enable the analysis and interpretation of astrophysical and planetary observations. Ammonia has been observed in the interstellar medium up to J=18 and more highly excited transitions are expected to appear in hot exoplanets and brown dwarfs. As a result, there is considerable interest in observing and assigning the high J (rovibrational) spectrum. In this work, numerous spectroscopic techniques were employed to study its high J transitions in the ground and ν2=1 states. Measurements were carried out using a frequency multiplied submillimeter spectrometer at Jet Propulsion Laboratory (JPL), a tunable far-infrared spectrometer at University of Toyama, and a high-resolution Bruker IFS 125 Fourier transform spectrometer (FTS) at Synchrotron SOLEIL. Highly excited ammonia was created with a radiofrequency discharge and a dc discharge, which allowed assignments of transitions with J up to 35. One hundred and seventy seven ground state and ν2=1 inversion transitions were observed with microwave accuracy in the 0.3–4.7 THz region. Of these, 125 were observed for the first time, including 26 ΔK=3 transitions. Over 2000 far-infrared transitions were assigned to the ground state and ν2=1 inversion bands as well as the ν2 fundamental band. Of these, 1912 were assigned using the FTS data for the first time, including 222 ΔK=3 transitions. The accuracy of these measurements has been estimated to be 0.0003–0.0006 cm−1. A reduced root mean square error of 0.9 was obtained for a global fit of the ground and ν2=1 states, which includes the lines assigned in this work and all previously available microwave, terahertz, far-infrared, and mid-infrared data. The new measurements and predictions reported here will support the analyses of astronomical observations by high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA. The comprehensive experimental rovibrational energy levels reported here will permit further refinement of the potential energy surface to improve ammonia ab initio calculations and facilitate assignment of new high-resolution spectra of hot ammonia.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

Pearson

Drouin

et al. 2010

The Journal of Chemical Physics

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“…Over the years, numerous studies have been undertaken to assign the complicated NH 3 spectrum (Poynter & Margolis 1983, 1984Sasada et al 1992;Kleiner et al 1999;Cottaz et al 2000;Lees et al 2008). Many studies are of cold NH 3 and are useful when studying planetary atmospheres in our solar system (Brown & Margolis 1996).…”

Section: Introductionmentioning

confidence: 99%

HOT NH₃SPECTRA FOR ASTROPHYSICAL APPLICATIONS

Hargreaves

Bernath

2011

ApJ

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We present line lists for ammonia (NH 3 ) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for twelve temperatures (300 -1300• C in 100• C intervals and 1370and each line list covers the 740 -2100 cm −1 range, which includes the majority of the ν 2 umbrella bending mode region (11 µm) and the ν 4 asymmetric bending mode region (6.2 µm). We also demonstrate the useful technique of obtaining empirical lower state energies from a set of spectra recorded at different sample temperatures. Using our NH 3 spectra, we have estimated lower state energies (E Low in cm −1 ) and our values have been incorporated into the line lists along with calibrated wavenumbers (ν in cm −1 ) and calibrated line intensities (S ′ in cm/molecule) for each line. We expect our hot NH 3 line lists to find direct application in the modelling of planetary atmospheres and brown dwarfs.

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“…Next, H i,k is diagonalized making use of a Lanczos tridiagonalization routine [34], thus obtaining the molecular vibrational levels. In this calculation, the values of the harmonic and anharmonic force constants, part of the expressions of both H 0 and H int , were regarded as variable parameters: f rr , F 2,2 , F 4,4 , [harmonic diagonal force constants for the local N-H stretch oscillator, the #2 (inversion) mode and the #4 (asymmetric bend)], x N H (anharmonic correction for the N-H stretch, related to the cubic anharmonic constant of the Morse potential), f (4) and f (6) (quartic and sextic corrections to the overall shape of the inversion mode potential), B,…”

Section: -D Computations On the Ammonia Vibrational Systemmentioning

confidence: 99%

“…Knowing its detailed ro-vibrational energy level structure, the planetary atmospheric temperatures could be determined [1]. For this reason, extensive spectroscopic measurements have been performed on 14 NH 3 as well as on its isotopomers [1][2][3][4][5][6], in a wide spectral range. Many theoretical studies have also been carried out to rationalize the extremely complicated NH 3 PES and ro-vibrational spectrum [2,3,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Complex symmetrized calculations on ammonia vibrational levels

2005

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This paper introduces a fully symmetrized Hamiltonian formalism designed for description of vibrational motion in ammonia (and any XH 3 molecule). A major feature of our approach is the introduction of complex basis vibrational wavefunctions in product form, satisfying the complex symmetry species (CSS) of the molecular symmetric top point group (D 3h ). The described formalism for ammonia is an adaptation of the approach, previously developed and applied to benzene, based on the CSS of the point group D 6h . The molecular potential energy surface (PES) is presented in the form of a Taylor series expansion around the planar equilibrium state. Using the described formalism, calculations have been carried out on the vibrational overtone and combination levels in 14 NH 3 up to vibrational excitation energies corresponding to the fourth N-H stretch overtone. The results from the calculations are adjusted to experimentally measured data, in order to determine the values of the harmonic and some anharmonic force constants of the molecular PES.

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Line Positions and Intensities in the 2ν2/ν4 Vibrational System of 14NH3 near 5–7 μm

Cited by 65 publications

References 37 publications

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

HOT NH₃SPECTRA FOR ASTROPHYSICAL APPLICATIONS

Complex symmetrized calculations on ammonia vibrational levels

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Line Positions and Intensities in the 2ν2/ν4 Vibrational System of 14NH3 near 5–7 μm

Cited by 65 publications

References 37 publications

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and ν2=1 states of ammonia

HOT NH3SPECTRA FOR ASTROPHYSICAL APPLICATIONS

Complex symmetrized calculations on ammonia vibrational levels

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HOT NH₃SPECTRA FOR ASTROPHYSICAL APPLICATIONS