Torsion‐Vibration‐Rotation Interactions in Methanol. III. Barrier Height in an Excited Vibrational State of CH3OH

1972 ◽  
Vol 57 (2) ◽  
pp. 824-826 ◽  
Author(s):  
R. M. Lees
Keyword(s):  
Barrier Height ◽  
Vibrational State ◽  
Excited Vibrational State ◽  
Torsion Vibration ◽  
Vibration Rotation

Millimetre wave spectrum of methyl mercaptan

1980 ◽  
Vol 58 (11) ◽  
pp. 1640-1648 ◽  
Author(s):  
R. M. Lees ◽  
M. Ali Mohammadi
Keyword(s):  
Interstellar Medium ◽  
Least Squares ◽  
Wave Spectrum ◽  
Methyl Mercaptan ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Millimetre Wave ◽  
Torsion Vibration ◽  
Vibration Rotation ◽  
Centrifugal Distortion Constants

An investigation of the rotational spectrum of CH332SH, one of the most recent molecules to be detected in the interstellar medium, has been carried out over the 25–107 GHz region. The frequencies of a-type Δk = 0 R-branch transitions have been measured for the J = 1 ← 0 up to J = 4 ← 3 multiplets for torsional states νt = 0–3. In addition, many P-, Q-, and R-branch transitions with Δk ≠ 0 have been identified in order to provide a catalogue of lines for potential radio astronomical applications. Improved values of rotational and centrifugal distortion constants, a-type torsion–vibration–rotation interaction constants, and torsional barrier parameters (V3 = 444.76 cm−1; effective V6 = −2.07 cm−1) have been determined from least-squares analyses of the spectra.

Diode laser spectra of the torsional splittings in the ν9 band of ethane: Torsion‐vibration‐rotation interactions and the barrier to internal rotation

1982 ◽  
Vol 77 (6) ◽  
pp. 2728-2744 ◽  
Author(s):  
J. Susskind ◽  
D. Reuter ◽  
D. E. Jennings ◽  
S. J. Daunt ◽  
W. E. Blass ◽  
...  
Keyword(s):  
Internal Rotation ◽  
Diode Laser ◽  
Torsion Vibration ◽  
Vibration Rotation

Electric dipole moment of H2O in the ν2 excited vibrational state

1981 ◽  
Vol 75 (10) ◽  
pp. 4869-4872 ◽  
Author(s):  
Hiroaki Kuze ◽  
Takayoshi Amano ◽  
Tadao Shimizu
Keyword(s):  
Dipole Moment ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Vibrational State ◽  
Excited Vibrational State

scholarly journals Circumstellar ammonia in oxygen-rich evolved stars

2018 ◽  
Vol 612 ◽  
pp. A48 ◽  
Author(s):  
K. T. Wong ◽  
K. M. Menten ◽  
T. Kamiński ◽  
F. Wyrowski ◽  
J. H. Lacy ◽  
...  
Keyword(s):  
Vibrational State ◽  
Ambient Medium ◽  
Far Infrared ◽  
Rotational Transition ◽  
Echelle Spectrograph ◽  
Vibrationally Excited ◽  
Excited Vibrational State ◽  
Very Large Array ◽  
Evolved Stars ◽  
Infrared Telescope

Context. The circumstellar ammonia (NH3) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH3 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 NH3 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 NH3 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 NH3 rovibrational absorption lines in the ν2 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 (v2 = 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 NH3 in the CSEs of these targets. Results. We detected NH3 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 NH3 is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH3 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 ten times higher than that in the carbon-rich CSE of IRC +10216. NH3 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. NH3 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 NH3. Future mid-infrared spectroscopy and radio imaging studies are necessary to constrain the radii and physical conditions of the formation regions of NH3.

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