Absolute rate constant measurements of CF(X{sup 2}II) reactions. 1. Reactions with O{sub 2}, F{sub 2}, Cl{sub 2}, and NO
- Katholieke Universiteit Leuven (Belgium); and others
Rate coefficients of the elementary reactions of CF(X{sup 2}II, v=O) with O{sub 2}, F{sub 2}, Cl{sub 2}, and NO at T = 294 K and p = 2-10 Torr (He or Ar bath gas) have been determined for the first time, using laser photodissociation/laser induced induced fluorescence (LIF) techniques. The CF(X{sup 2}II) radicals were generated by excimer laser photolysis of CF{sub 2}Br{sub 2} at 248 nm. Exponential decays of CF(X, v=0) were monitored by LIF (A{sup 2}{Sigma}{sup +}, v{prime}=1{l_arrow}X{sup 2}II, v{double_prime}=0 transition) at varying concentrations of the reactant, in very large excess over CF. The rate constant for each of the title reactions was found to be independent of pressure in the 2-10-Torr range: k(O{sub 2}) = (1.6 {+-} 0.2) x 10{sup -12}; k(F{sub 2}) = (3.9 {+-}0.4) x 10{sup -12}; k(Cl{sub 2}) = (1.7 {+-} 0.2) x 10{sup -11}, and k(NO) = (2.1 {+-} 0.2) x 10{sup -11} cm{sup 3} molecule{sup -1} s{sup -1}. Besides, an upper limit K {le} 10{sup 14} was established for the reactions of CF(X) with H{sub 2}, CH{sub 4}, C{sub 2}H{sub 2}, CF{sub 4}, and CO{sub 2}. In general, the rate coefficients obtained for the investigated CF(X{sup 2}II) reactions are close to literature data on CCl and CBr analogues but far below reported rate constants of corresponding CH(X{sup 2}II) reactions are close to literature data on CCl and CBr analogues but far below reported rate constants of corresponding CH(X{sup 2}II) processes, specifically regarding reactions with closed-shell molecules. The exceptional stability and concomitantly low reactivity of CF-relative to CH-can be attributed to strong back-donation from one of the fluorine 2p{pi} orbitals into the vacant carbon 2p{pi} orbital. 33 refs., 8 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 379466
- Journal Information:
- Journal of Physical Chemistry, Vol. 96, Issue 3; Other Information: PBD: 6 Feb 1992
- Country of Publication:
- United States
- Language:
- English
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