Absolute rate data for reactions of ground-state atomic calcium, Ca(4s sup 2 sup 1 S sub 0 ), at elevated temperatures determined by time-resolved atomic resonance absorption spectroscopy

Journal Article · Sun Sep 01 00:00:00 EDT 1991 · Combustion and Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(91)90130-4· OSTI ID:5524598

Clay, R S; Husain, D ^[1]

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1. Dept. of Chemistry, Univ. of Cambridge, Cambridge CB2 1 EW (GB)

This paper reports on reactions of ground-state atomic calcium, Ca(4s{sup 2}{sup 1}S{sub 0}), with a large number of collision partners investigated by direct spectroscopic measurement using atomic resonance absorption spectroscopy in the time-domain. Ca(4{sup 1}S{sub 0}) was generated by the pulsed irradiation of CaI{sub 2} vapor at elevated temperatures and monitored photoelectrically in the single-shot mode using the resonance transition at {lambda} = 422.7 nm Ca(4{sup 1}P{sub 1}) {l arrow} Ca(4{sup 1}S{sub 0}). Decay profiles in the presence of the gases CH{sub 3}Cl, C{sub 2}H{sub 5}Cl, CF{sub 3}Cl, CF{sub 3}Br, CF{sub 2}Cl{sub 2}, CH{sub 3}F, CF{sub 3}H, CR{sub 4}, SF{sub 6}, HCl, HBr, N{sub 2}O with excess helium buffer gas were captured in a transient recorder and transferred either directly to a microcomputer or mainly to an XY-recorder for subsequent kinetic analysis. The development of the present method was principally feasible because of the construction here of an extremely intense, high-current hollow cathode atomic resonance source for the calcium transition employed in the investigation. Although the kinetic measurements for the removal of Ca(4{sup 1}S{sub 0}) with H{sub 2}O showed consistent plots, these yielded a value of k{sub R}(T = 911 K) = (3.4 {plus minus} 0.2) {times} 10{sup {minus}12} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, which is viewed with caution as it implies a bond dissociation energy of D(Ca-OH) of a magnitude at the extreme limits of the largest value reported from various analyses on calcium in premixed H{sub 2}-O{sub 2}-N{sub 2} flames.

• OSTI ID: 5524598
• Journal Information: Combustion and Flame; (United States), Vol. 86:4; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
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CALCIUM
ATOM-ATOM COLLISIONS
CALCIUM IODIDES
PULSED IRRADIATION
HALOGENATED AROMATIC HYDROCARBONS
CHEMICAL REACTION KINETICS
FLAMES
ABSORPTION SPECTRA
DECAY
GASES
GROUND STATES
HOLLOW CATHODES
HYDROBROMIC ACID
HYDROCHLORIC ACID
METHYL CHLORIDE
NITROUS OXIDE
SULFUR FLUORIDES
WATER
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
AROMATICS
ATOM COLLISIONS
BROMINE COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CATHODES
CHALCOGENIDES
CHLORINATED ALIPHATIC HYDROCARBONS
CHLORINE COMPOUNDS
COLLISIONS
ELECTRODES
ELEMENTS
ENERGY LEVELS
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IODIDES
IODINE COMPOUNDS
IRRADIATION
KINETICS
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SPECTRA
SULFUR COMPOUNDS
664300* - Atomic & Molecular Physics- Collision Phenomena- (1992-)
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