Imaging the Stereodynamics of Cl + CH4(ν3 = 1): Polarization Dependence on the Rotational Branch and the Hyperfine Depolarization.
The transition state in the Cl + CH4 reaction is of Cl-H-C collinear geometry, which serves as the bottleneck to reaction. When the reactant CH4 is antisymmetrically stretch-excited to ν3 = 1 by absorbing a linearly polarized photon, all four C-H bonds are collectively excited, and any one of the H atoms could be attacked by the Cl atom. At first sight, it is not obvious how an excited spherical-top molecule like CH4 is aligned and what consequences will be on chemical reactivity by polarizing the CH4 reagents. As shown here, an enormous steric effect on reactivity is observed, which depends sensitively on the selected rotational states. By exploiting various rotational branches in optical excitation, we quantify the degree of stereospecificity for a few lowest rovibrational states of the aligned CH4(ν3 = 1) reagents, as well as account for the hyperfine depolarization factor. This information lays the foundation for a full stereorequirement study of the Cl + CH4(ν3 = 1) reaction.
†Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617.
Huilin
H
Pan
†Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617.
Jiayue
J
Yang
†Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617.
Fengyan
F
Wang
†Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617.|‡Department of Physics, National Taiwan University, Taipei, Taiwan 10617.
Kopin
K
Liu
crossed molecular beams; hyperfine depolarization effect; polarization-dependent differential cross section; product pair correlation; stereodynamics; time-sliced velocity map imaging