Hyperfine Structure of Rotation-Inversion Levels in the Excited ν2State of Ammonia

Белов, С. П.; Urban, Štěpán; Winnewisser, G.

doi:10.1006/jmsp.1997.7516

Cited by 26 publications

(15 citation statements)

References 24 publications

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“…The operator code for this interaction is 600VV in the SPFIT/ SPCAT programs A total of 4394 transitions were included in the current analysis, including 2166 transitions assigned in this study and 2228 transitions from previous microwave studies 16,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] and infrared studies. [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] Each of the 4394 transitions was weighed by its experimental uncertainty.…”

Section: Resultsmentioning

confidence: 99%

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%

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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“…There have been many previous microwave studies of the inversion and ro-inversion transitions [42][43][44][45][46][47]30,[48][49][50][51][52]. A summary of the microwave investigations of the ground state inversion spectra prior to 1975 is provided by Poynter and Kakar [48].…”

Section: Introductionmentioning

confidence: 97%

“…Since then, ammonia has been one of the first molecules investigated by microwave spectroscopy [9] and the molecule used in the first maser [10,11]. It has also served as the test case for a wide array of infrared spectroscopic techniques including infrared-microwave double resonance [12][13][14][15], Laser Stark Spectroscopy [16][17][18][19], two photon spectroscopy [14,[20][21][22], IR heterodyne spectroscopy [23][24][25][26][27], saturation spectroscopy [28][29][30], laser side-band [29,31], and IR-IR double resonance [32,33].…”

Section: Introductionmentioning

confidence: 98%

Measurements of 14NH3 in the ν2=1 state by a solid-state, photomixing, THz spectrometer, and a simultaneous analysis of the microwave, terahertz, and infrared transitions between the ground and ν2 inversion–rotation levels

Chen

Pearson

Pickett

et al. 2006

Journal of Molecular Spectroscopy

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“…(1) Kukolich (1967); (2) Kukolich & Wofsy (1970); (3) Poynter & Kakar (1975); (4) Belov et al (1998); (5) Cazzoli et al (2009); (6) Winnewisser et al (1996); (7) Yu et al (2010).…”

Section: Mid-infrared Rovibrational Transitionsmentioning

confidence: 99%

Circumstellar ammonia in oxygen-rich evolved stars

Wong

Menten

Kamiński

et al. 2018

A&A

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Context. The circumstellar ammonia (NH 3 ) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH 3 abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. Aims. We would like to characterise the spatial distribution and excitation of NH 3 in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. Methods. We observed NH 3 emission from the ground state in the inversion transitions near 1.3 cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH 3 rovibrational absorption lines in the ν 2 band near 10.5 µm with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). We also attempted to search for the rotational transition within the excited vibrational state ( 2 = 1) near 2 mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH 3 in the CSEs of these targets. Results. We detected NH 3 inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH 3 is similar to that of assorted molecules, such as SO and SO 2 , that exhibit localised and clumpy emission. Our modelling shows that the NH 3 abundance relative to molecular hydrogen is generally of the order of 10 −7 , which is a few times lower than previous estimates that were made without considering radiative pumping and is at least 10 times higher than that in the carbon-rich CSE of IRC +10216. NH 3 in OH 231.8+4.2 and IRC +10420 is found to emit in gas denser than the ambient medium. Incidentally, we also derived a new period of IK Tau from its V-band light curve. Conclusions. NH 3 is again detected in very high abundance in evolved stars, especially the oxygen-rich ones. Its emission mainly arises from localised spatial-kinematic structures that are probably denser than the ambient gas. Circumstellar shocks in the accelerated wind may contribute to the production of NH 3 . Future mid-infrared spectroscopy and radio imaging studies are necessary to constrain the radii and physical conditions of the formation regions of NH 3 .

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Hyperfine Structure of Rotation-Inversion Levels in the Excited ν2State of Ammonia

Cited by 26 publications

References 24 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

Measurements of 14NH3 in the ν2=1 state by a solid-state, photomixing, THz spectrometer, and a simultaneous analysis of the microwave, terahertz, and infrared transitions between the ground and ν2 inversion–rotation levels

Circumstellar ammonia in oxygen-rich evolved stars

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