Direct Measurements of Rate Coefficients for the Reaction of Ethynyl Radical (C2H) With C2H2 at 90 and 120 K Using a Pulsed Laval Apparatus

Published

June 1, 2000

Author(s)

S Lee, D A. Samuels, R J. Hoobler, S R. Leone

Abstract

Rate coefficients for the reaction C₂H + C₂H₂ -> C₄H₂ + H are measured at 90 and 120 K by using a new pulsed Laval nozzle apparatus equipped with laser ionization, time-of-flight mass spectrometric detection. The C₂H radicals are generated by 193 nm laser photolysis of C₂H₂, and the reaction product, C₄H₂ is directly detected by single-photon ionization at 118 nm (10.5 eV). Rate coefficients of (2.7 0.5) X 10^-10 and (2.5 0.4) X 10⁰¹⁰ cm³ molecule ^-1_s^-1 are obtained at 90 and 120 K, compared to the room temperature value of 1.3 x 10^{010 cm}u3^ molecule^-1x^-1. The results show a significant negative temperature dependence of the reaction rate coefficient below room temperature. The implications for models of planetary atmospheres, such as for Titan, are discussed.

Citation

Journal of Geophysical Research

Volume

105

Issue

No. E6

Pub Type

Journals

Keywords

acetylene, rate coefficient, Titan

Citation

Lee, S. , Samuels, D. , Hoobler, R. and Leone, S. (2000), Direct Measurements of Rate Coefficients for the Reaction of Ethynyl Radical (C₂H) With C₂H₂ at 90 and 120 K Using a Pulsed Laval Apparatus, Journal of Geophysical Research (Accessed October 28, 2025)