Thermal energy reactions of CO+2 with chloromethanes

Abstract

Rate constants and product ions have been determined for thermal energy reactions of CO2+ with CHnCl4−n(n=0–3) by using an ion-beam apparatus. Total rate constants are (8.7±3.7), (6.7±3.1), (9.1±4.1), and (4.9±1.6)×10−10 cm3 s−1 for CH3Cl, CH2Cl2, CHCl3, and CCl4, respectively. These values amount to 38%–61% of the collision rate constants estimated from either the Langevin or averaged dipole oriented theory. Although charge transfer followed by the successive loss of a Cl atom is the major product channel, parent ions are formed from CH3Cl and CH2Cl2 with branching ratios of 33%±5% and 25%±3%, respectively. The reaction mechanisms are interpreted in terms of the electronic states of the parent molecular ion accessible in the charge-transfer processes. The lack of formation of parent ions from CHCl3 and CCl4 is explained as due to complete (pre)dissociation of ionic states below 13.78 eV.