Depression of reactivity by the collision energy in the single barrier H + CD 4 → HD + CD 3 reaction

• DOI: 10.1073/pnas.1006910107
• Publication Date: 2010-07-07T02:23:58Z
• Authors: Weiqing Zhang; Yong Zhou; Guorong Wu; Yunpeng Lu; Huilin Pan; Bina Fu; Quan Shuai; Lan Liu; Shu Liu; Liling Zhang; Bo Jiang; Dongxu Dai; Soo-Ying Lee; Zhen Xie; Bastiaan J. Braams; Joel M. Bowman; Michael A. Collins; Dong H. Zhang; Xueming Yang
• Keywords: chemical reaction; collision energy; Cross section; atom; article; Potential energy surface; Quantum scattering; 7. Clean energy; 01 natural sciences; crossed beams scattering technique; mathematical analysis; technique Chemical reaction dynamics; 0104 chemical sciences; quantum chemistry; priority journal; Keywords: hydrogen; Crossed molecular beam equipment; energy

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.