Multidimensional steric effect for the XeBr* (B, C) formation in the oriented Xe*(3P2, MJ=2)+oriented CF3Br reaction.

Steric effect for the XeBr^* (B, C) formation in the oriented Xe^*(³P₂, M_J=2)+oriented CF₃Br reaction has been observed as a function of the mutual configuration between the molecular orientation and the atomic orientation in the collision frame. Molecular steric opacity function has been determined as a function of the atomic orbital alignment (L_Z^′) in the collision frame. The L_Z^′ selectivity in the molecular steric opacity function is different between the XeBr^* (B, C) channels: For the XeBr^* (C) channel, the L_Z^′=0 alignment is favorable at the molecular axis direction and the |L_Z^′|=1 alignment is favorable at the sideway direction, whereas for the XeBr^* (B) channel, the L_Z^′=0 alignment is favorable at the sideway direction and the |L_Z^′|=1 alignment is favorable at the molecular axis direction. However, the shape of the steric opacity function for the XeBr^* (B) channel at the L_Z^′=0 (and |L_Z^′|=1) alignment is similar to that for the XeBr^* (C) channel at the |L_Z^′|=1 (and L_Z^′=0) alignment, respectively: A large molecular orientation dependence (i.e., the largest reactivity at the Br-end with the small molecular alignment dependence) is recognized for the XeBr^* (B) channel at the L_Z^′=0 alignment and for the XeBr^* (C) channel at the |L_Z^′|=1 alignment, whereas a large molecular alignment dependence (i.e., the largest reactivity at the Br-end with the poor reactivity at the sideway) is recognized for the XeBr^* (B) channel at the |L_Z^′|=1 alignment and for the XeBr^* (C) channel at the L_Z^′=0 alignment. We propose the indirect mechanism for the dark channels (Xe+Br+CF₃) via the back-electron transfer from the CF₃ segment (or dissociating CF₃...Br^-) to Xe⁺ as the origin of the significant molecular alignment dependence in the molecular steric opacity function. [ABSTRACT FROM AUTHOR]