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State-to-state dynamics and doubly differential cross sections of the reaction of chlorine atoms with CH4(v3=1, J)
Author(s): William R. Simpson; Andrew J. Orr-Ewing; Richard N. Zare
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Paper Abstract

A mixture of methane and chlorine molecules in a helium carrier is expanded into a vacuum chamber using a pulsed valve. Polarized laser photolysis of Cl2 at 355 nm is used to produce chlorine atoms with a sharply peaked speed distribution and a known angular distribution. Methane molecules are excited in the v3 mode by infrared absorption on the R(O) fundamental transition, which results in methane in the v3 equals 1, J equals 1 state. Following a 100 ns time delay to allow for reaction, HCl (v' equals 1, J') product molecules are detected by (2 + 1) resonance enhanced multiphoton ionization (REMPI). The resulting photoions are detected with both mass and velocity resolution using a linear time-of-flight mass spectrometer (TOF-MS). An analysis of the time dependence of the ion signal allows us to determine the differential scattering cross section for the specific rovibrational state ionized. The TOF data show a change in the product angular distribution with J', and thus demonstrate the importance of measuring doubly differential cross sections for elucidating the dynamics of this reaction system.

Paper Details

Date Published: 22 April 1993
PDF: 12 pages
Proc. SPIE 1858, Laser Techniques for State-Selected and State-to-State Chemistry, (22 April 1993); doi: 10.1117/12.143111
Show Author Affiliations
William R. Simpson, Stanford Univ. (United States)
Andrew J. Orr-Ewing, Stanford Univ. (United States)
Richard N. Zare, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 1858:
Laser Techniques for State-Selected and State-to-State Chemistry
Cheuk Yiu Ng, Editor(s)

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