氯代甲烷分子对电子激发态CH（A^2Δ，B^2Σ~－和C^2Σ~＋）的猝灭

Quenching of CH(A￣2Δ, B￣Σ￣-and C￣2Σ￣+)radicals by chloromethanes

本文用激光光解－荧光猝灭方法测定了ＣＨ３Ｃｌ对ＣＨ（Ａ，Ｂ和Ｃ）及ＣＨ２Ｃｌ２、ＣＨＣｌ３和ＣＣｌ４对ＣＨ（Ｃ）的猝灭速率常数。结果表明，氯代甲烷分子对ＣＨ（Ｃ）的猝又速率常数近似于ＣＨ（Ｂ）的猝灭速率常数，而比ＣＨ（Ａ）的猝灭速率常数大，但都具有与气动速率相当的量级，表明化学反应在其中可能起着重要的作用，且ＣＨ（Ａ，Ｂ，Ｃ）的猝灭速率常数都随氯代甲烷分子中的Ｃ－Ｃｌ键数的增加而增大。我们用碰撞络合物模型计算了氯代甲烷分子与ＣＨ（Ａ，Ｂ）形成碰撞络合物时的生成截面，结果表明在电子激发态ＣＨ的猝灭过程中多极吸引势起着重要作用，且该过程属于入口通道控制的猝灭机制。

AbstractThe quenching rate constants of CH (A, B, C) by CH3Cl and CH (C) by CH2Cl2, CHCl3 and CCl4 were measured at room temperature by means of laser photodissoctation-fluorescence quenching technique. It is found that for chloromethane molecules CH(C) quenching rate constants are similar to those for CH(B) quenching and both are larger than those for CH (A) quenching, but they all are of the order of the gas kinetic collision rate. This implies that the quenching may be latgely by chemical reaction rather than by Physical quenching. In addition, the quenching rate constants for CH(A, B,C) increase with the increasing number of C-Cl bonds contained in chloromethsne molecules. The formation cross sections of complexes between CH(A, B) and chloromethane molecules are calculated using collision complex model. The results would suggest that the quenching processes of electronically exited CH are entrance-channel controlled.