Rate coefficients of C{sub 2}H with C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, and H{sub 2} from 150 to 359 K
- National Inst. of Standards and Technology, Boulder, CO (United States)
Rate coefficients for the reactions C{sub 2}H with C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, and H{sub 2} are measured over the temperature range 150-359 K using transient infrared laser absorption spectroscopy. The ethynyl radical is formed by photolysis of C{sub 2}H{sub 2} with a pulsed excimer laser at 193 nm, and its transient absorption is monitored with a color center laser on the Q{sub 11}(9) line of the A{sup 2}{Pi}-X{sup 2}{Sigma} transition at 3593.68 cm{sup -1}. Over the experimental temperature range 150-359 K the rate constants of C{sub 2}H with C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, and H{sub 2} can be fit to the Arrhenius expressions k{sub C(2)H(4)} = (7.*{+-}0.6) x 10{sup -11} exp[(134{+-}44)/T], k{sub C(2)H(6)} = (3.5{+-}0.3) x 10{sup -11} exp[(2.9{+-}16)/T], and k{sub H(2)} = (1.2{+-}0.3) x 10{sup -11} exp[(-998{+-}57)]/T cm{sup 3} molecule{sup -1} s{sup -1}, respectively. The data for C{sub 2}H with C{sub 2}H{sub 4} and C{sub 2}H{sub 6} indicate a negligible activation energy to product formation shown by the mild negative temperature dependence of both reactions. When the H{sub 2} data are plotted together with the most recent high-temperature results from 295 to 854 K, a slight curvature is observed. The H{sub 2} data can be fit to the non-Arrhenius form k{sub H(2)} = 9.2 x 10{sup -18}T{sup 2.17{+-}0.50} exp[(-478{+-}165)/T] cm{sup 3} molecule{sup -1} s{sup -1}. 33 refs., 8 figs., 4 tabs.
- OSTI ID:
- 458666
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 51 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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