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 Cl(P-2(3/2)) With a sharply peaked speed distribution and a known angular distribution. Methane molecules are excited in the asymmetric stretch mode by infrared absorption to the nu3=1, J=1 state. Following a 100 ns time delay to allow for reaction, HCl(v'= 1, J') product molecules are probed by (2+1) resonance-enhanced multiphoton ionization. The resulting photoions are detected with both mass and velocity resolution using a linear time-of-flight mass spectrometer. Application of the methods described by Shafer et al., allows determination of the differential cross section for the specific rovibrational state ionized at a center-of-mass collision energy of 0.159 eV. The time-of-flight data show a change in the product angular distribution with J' and thus demonstrate the importance of measuring quantum-state-resolved differential cross sections for elucidating the dynamics of this reaction system.
|Number of pages
|Chemical Physics Letters
|Published - 3 Sept 1993
- ENHANCED MULTIPHOTON IONIZATION
- PULSED SUPERSONIC JET