Infrared spectroscopy of CO sub 2 --D(H)Br: Molecular structure and its reliability

Journal Article · Thu Oct 15 00:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463799· OSTI ID:7246769

Zeng, Y P; Sharpe, S W; Shin, S K; Wittig, C; Beaudet, R A ^[1]

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1. Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482 (United States)

A high resolution rovibrational absorption spectrum of the weakly bonded CO{sub 2}--DBr complex has been recorded in the 2350 cm{sup {minus}1} region by exciting the CO{sub 2} asymmetric stretch vibration with a tunable diode laser. The CO{sub 2}--DBr band origin associated with this mode is 2348.2710 cm{sup {minus}1}, red-shifted by 0.87 cm{sup {minus}1} from uncomplexed CO{sub 2}. The position of the hydrogen atom is determined from differences in moments-of-inertia between CO{sub 2}--DBr and CO{sub 2}--HBr, i.e., by using the Kraitchman method. From this, we conclude that ground state CO{sub 2}--H(D)Br has an average geometry that is planar and inertially T-shaped, with essentially parallel HBr and CO{sub 2} axes. Average values of intermolecular parameters are: {ital R}{sub cm}=3.58 A, {theta}{sub BrCO}=79.8{degree}, and {theta}{sub HBrC}=93.1{degree}. The validity of using the Kraitchman method, which was designed for use with rigid molecules, with a floppy complex like CO{sub 2}--HBr is discussed. The experimental structure is corroborated qualitatively by results from Moller--Plesset second-order perturbation calculations, corrected for basis set superposition errors. The theoretical equilibrium geometry for the inertially T-shaped complex is planar with structural parameters: {ital R}{sub CBr}=3.62 A, {theta}{sub BrCO}=89{degree}, and {theta}{sub HBrC}=86{degree}. A number of cuts on the four dimensional intermolecular potential surface confirm large zero-point amplitudes, which are known to be characteristic of such systems, and these cuts are used to estimate tunneling splittings. Tunneling is shown to occur by out-of-plane rotation of the H atom, in accord with the experimental observations of Rice {ital et} {ital al}. There is no significant in-plane tunneling.

• DOE Contract Number: FG03-89ER14053
• OSTI ID: 7246769
• Journal Information: Journal of Chemical Physics; (United States), Vol. 97:8; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
BROMIDES
VIBRATIONAL STATES
CARBON DIOXIDE
DEUTERIUM COMPOUNDS
ABSORPTION SPECTRA
ASYMMETRY
CHEMICAL BONDS
COMPLEXES
COORDINATES
EQUILIBRIUM
GEOMETRY
HYDROGEN
LASERS
PERTURBATION THEORY
PHOTOCHEMISTRY
RESOLUTION
TUNING
BROMINE COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMISTRY
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
MATHEMATICS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
SPECTRA
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)