Depression of reactivity by the collision energy in the single barrier H + CD4 -> HD + CD3 reaction.
Crossed molecular beam experiments and accurate quantum scattering calculations have been carried out for the polyatomic H + CD(4) --> HD + CD(3) reaction. Unprecedented agreement has been achieved between theory and experiments on the energy dependence of the integral cross section in a wide collision energy region that first rises and then falls considerably as the collision energy increases far over the reaction barrier for this simple hydrogen abstraction reaction. Detailed theoretical analysis shows that at collision energies far above the barrier the incoming H-atom moves so quickly that the heavier D-atom on CD(4) cannot concertedly follow it to form the HD product, resulting in the decline of reactivity with the increase of collision energy. We propose that this is also the very mechanism, operating in many abstraction reactions, which causes the differential cross section in the backward direction to decrease substantially or even vanish at collision energies far above the barrier height.
Zhang
Weiqing
W
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, PR China.
Zhou
Yong
Y
Wu
Guorong
G
Lu
Yunpeng
Y
Pan
Huilin
H
Fu
Bina
B
Shuai
Quan
Q
Liu
Lan
L
Liu
Shu
S
Zhang
Liling
L
Jiang
Bo
B
Dai
Dongxu
D
Lee
Soo-Ying
SY
Xie
Zhen
Z
Xie
Zeng
Z
Braams
Bastiaan J
BJ
Bowman
Joel M
JM
Collins
Michael A
MA
Zhang
Dong H
DH
Yang
Xueming
X