Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface
- Department of Chemistry, University of California, and Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (USA)
Two new intermolecular vibration--rotation-tunneling (VRT) bands of Ar--NH{sub 3} have been measured using tunable far infrared laser spectroscopy. We have unambiguously assigned these and a previously measured FIR band (Gwo {ital et} {ital al}., Mol. Phys. {bold 71}, 453 (1990)) as {Pi}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), {Sigma}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), and {Sigma}(0{sub 0}, {ital n}=1){l arrow}{Sigma}(0{sub 0}, {ital n}=0). The three upper states of these are found to be strongly mixed by anisotropy and Coriolis effects. A simultaneous least squares fit of all transitions has yielded vibrational frequencies, rotational and centrifugal distortion constants, and a Coriolis parameter as well as quadrupole hyperfine coupling constants for the upper states. An effective angular potential energy surface for Ar--NH{sub 3} in its lowest stretching state has been determined from these data, after explicitly accounting for the effects of bend stretch interactions. Features of the surface include a global minimum at the near T-shaped configuration ({theta}=90{degree}), a 30 cm{sup {minus}1} to 60 cm{sup {minus}1} barrier to rotation at {theta}=180{degree} (or 0{degree}), and a very low barrier or possibly a secondary minimum at {theta}=0{degree} (or 180{degree}). Both attractive and repulsive interactions are shown to contribute significantly to the anisotropic forces in the complex. Comparison with {ital ab} {ital initio} calculations are presented.
- OSTI ID:
- 5467385
- Journal Information:
- Journal of Chemical Physics; (USA), Vol. 95:1; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ARGON COMPLEXES
INFRARED SPECTRA
ADDUCTS
AMMONIA
ARGON
POTENTIAL ENERGY
ROTATIONAL STATES
VIBRATIONAL STATES
COMPLEXES
ELEMENTS
ENERGY
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
HYDRIDES
HYDROGEN COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
RARE GASES
SPECTRA
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory
400102 - Chemical & Spectral Procedures