Wr. Simpson et al., STATE-TO-STATE DIFFERENTIAL CROSS-SECTIONS FOR THE REACTION CL((2)P(32))+CH4(NU-3=1,J=1)-]HCL(NU'=1,J')+CH3/, Chemical physics letters, 212(1-2), 1993, pp. 163-171
A mixture of methane and chlorine molecules in a helium carrier is exp
anded into a vacuum chamber using a pulsed valve. Polarized laser phot
olysis 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 m
olecules are excited in the asymmetric stretch mode by infrared absorp
tion to the nu3=1, J=1 state. Following a 100 ns time delay to allow f
or reaction, HCl(v'= 1, J') product molecules are probed by (2+1) reso
nance-enhanced multiphoton ionization. The resulting photoions are det
ected with both mass and velocity resolution using a linear time-of-fl
ight mass spectrometer. Application of the methods described by Shafer
et al., allows determination of the differential cross section for th
e specific rovibrational state ionized at a center-of-mass collision e
nergy of 0.159 eV. The time-of-flight data show a change in the produc
t angular distribution with J' and thus demonstrate the importance of
measuring quantum-state-resolved differential cross sections for eluci
dating the dynamics of this reaction system.