Proctor David L, Davis H Floyd
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA.
Proc Natl Acad Sci U S A. 2008 Sep 2;105(35):12673-7. doi: 10.1073/pnas.0801170105. Epub 2008 Aug 4.
The reaction Y + CH(4) --> HYCH(3) --> YCH(2) + H(2) is initiated by C-H insertion involving a 20 +/- 3 kcal/mol potential energy barrier. The reaction is studied in crossed molecular beams under two different conditions with nearly the same total energy. One experiment is carried out at a collision energy of 15.1 kcal/mol with one quantum of CH(4) antisymmetric (nu(3)) stretching vibrational excitation (8.63 kcal/mol), the other at a collision energy of 23.8 kcal/mol. The reaction cross-section for C-H stretch excited methane (sigma(s)) is found to be at least a factor of 2.2 times larger than for ground-state methane (sigma(g)) at the same total energy.
反应Y + CH₄ → HYCH₃ → YCH₂ + H₂由涉及20±3千卡/摩尔势能垒的C-H插入引发。该反应在交叉分子束中于两种几乎具有相同总能量的不同条件下进行研究。一个实验在15.1千卡/摩尔的碰撞能量下进行，甲烷具有一个量子的反对称（ν₃）伸缩振动激发（8.63千卡/摩尔），另一个实验在23.8千卡/摩尔的碰撞能量下进行。发现在相同总能量下，C-H伸缩激发甲烷的反应截面（σₛ）比基态甲烷的反应截面（σ₉）至少大2.2倍。
