Rotationally and translationally resolved hot atom collisional excitation of the CO sub 2 Fermi mixed bend/stretch vibrational levels by time-dependent diode laser spectroscopy
- Department of Chemistry, Columbia University, New York, NY (USA) Columbia Radiation Laboratory, Columbia University, New York, NY (USA)
- Department of Chemistry, Brookhaven National Laboratory, Upton, NY (USA)
High resolution IR diode laser absorption spectroscopy is employed to monitor the nascent rotational population distributions and transient linewidths in the Fermi mixed symmetric stretch/overtone bend vibrational mode of CO{sub 2} (10{sup 0}0/02{sup 0}0) following collisions with translationally hot hydrogen and deuterium atoms, produced from the 193 nm excimer laser photolysis of H{sub 2}S or D{sub 2}S. The nascent 10{sup 0}0/02{sup 0}0 rotational distribution produced by H* atom collisional excitation peaks at {ital J}{similar to}26 and is well fit by a 747 K Boltzmann distribution. The transient linewidths are 1.5--3 times the ambient, room temperature CO{sub 2} Doppler linewidths, are{similar to}0.002 cm{sup {minus}1} larger for D* atom collisions than H* atom collisions, and increase with increasing rotational quantum number. The experimentally determined relative cross sections for H* atom collisional excitation of CO{sub 2} vibrational states are as follows: 00{sup 0}1 antisymmetric stretch: 10{sup 0}0 Fermi mixed upper level: 02{sup 0}0 Fermi mixed lower level: 02{sup 2}0 bend{approx}1.0 : 0.6 : 0.6 : 0.4. The absolute cross section for inelastic collisional scattering of CO{sub 2} by H* atoms into 10{sup 0}0 {ital J}=38 is (1.4{plus minus}0.8){times}10{sup {minus}2} A{sup 2}, and the total excitation cross section for the 10{sup 0}0 vibrational state is 0.37{plus minus}0.21 A{sup 2}. A statistical model and a simple quantized Landau--Teller model are unable to explain qualitatively the observed data; however, a breathing ellipsoid model, coupled with an IOS quantum scaling relation, reproduces the major features in the experimental data for both the 10{sup 0}0/02{sup 0}0 and 00{sup 0}1 states. The differences in the experimental data for distinct vibrational motions can be attributed to hot atoms sampling different regions of the potential surface.
- DOE Contract Number:
- FG02-88ER13937
- OSTI ID:
- 6234042
- Journal Information:
- Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 93:7; ISSN JCPSA; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
COLLISIONS
CROSS SECTIONS
DEUTERIUM
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FERMI LEVEL
HYDROGEN
HYDROGEN ISOTOPES
INFRARED SPECTRA
ISOTOPES
LASER SPECTROSCOPY
LIGHT NUCLEI
LINE WIDTHS
MOLECULE COLLISIONS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
OXIDES
OXYGEN COMPOUNDS
QUANTUM NUMBERS
ROTATIONAL STATES
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
VIBRATIONAL STATES