论文标题
在低温下气相CH + CO2反应的隧穿增强
Tunneling Enhancement of the Gas-Phase CH + CO2 Reaction at Low Temperature
论文作者
论文摘要
通过光原子的量子机械隧穿，在低温下中性物种之间许多激活反应的速率增加。尽管涉及分子或重原子的隧道过程在凝结相中是众所周知的，但从未在实验中证明类似的气相过程。在这里，我们研究了超音速反应器中激活的CH + CO2-> HCO + CO反应，测量速率常数迅速增加以下100K。从机械上讲，通过CH插入CH中的隧穿，并通过速率计算准确地重现了实验值。为了排除H原子隧道的可能性，将CD用于其他实验和计算中。令人惊讶的是，当零点能量效应消除了产物形成的障碍时，等效的CD + CO2反应在低温下加速。总之，重粒子隧道效应可能是CH + CO2反应在较低温度下观察到的反应性增加的原因，而CD + CO2反应的等效效应是由淹没的屏障相对于反应物而产生的。
The rates of numerous activated reactions between neutral species increase at low temperatures through quantum mechanical tunneling of light hydrogen atoms. Although tunneling processes involving molecules or heavy atoms are well known in the condensed phase, analogous gas-phase processes have never been demonstrated experimentally. Here, we studied the activated CH + CO2 -> HCO + CO reaction in a supersonic flow reactor, measuring rate constants that increase rapidly below 100 K. Mechanistically, tunneling is shown to occur by CH insertion into the C-O bond, with rate calculations accurately reproducing the experimental values. To exclude the possibility of H-atom tunneling, CD was used in additional experiments and calculations. Surprisingly, the equivalent CD + CO2 reaction accelerates at low temperature as zero point energy effects remove the barrier to product formation. In conclusion, heavy-particle tunneling effects might be responsible for the observed reactivity increase at lower temperatures for the CH + CO2 reaction, while the equivalent effect for the CD + CO2 reaction results instead from a submerged barrier with respect to reactants.
