Temperature, Kinetic Energy, and Rotational Temperature Effects in Four ReactionsInvolving Isotopes

摘要

Data on four reactions involving isotopes taken in a variable temperature-selected ion flow drift tube are presented. A study of the reaction of O(-) with N (sub 2) O indicates that the reaction proceeds preferentially by bonding of the O(-) to the central nitrogen in N (sub 2) O. The preference for O(-) attack at the central nitrogen over attack at the terminal nitrogen decreases at higher temperatures. In the atom abstraction reaction of O(+) with HD, OH(+) is formed more efficiently than is OD(+) at low temperatures and moderate energy. The branching fraction favoring OH(+) production is also sensitive to the rotational temperature of the HD. The results for this reaction are consistent with a model of the reaction based on the long range part of the ion-neutral potential. Rate constants for the reactions of O(-) with H (sub 2), D (sub 2), and HD vary with mass of the hydrogen molecule as predicted from the collision rate constant dependence. These reactions proceed by two channels: hydrogen abstraction and associative electron detachment. The rate constant for the minor hydrogen abstraction channel increases with increasing kinetic energy. The efficiency of the abstraction reaction of O(-) with D(sub 2) is significantly smaller than that in the reaction with H sub 2. More OD(-) as compared with OH(-) is produced in the reaction of HD. The results are explained by a direct two step mechanism. A large preference for OH(-) over OD(-) formation in the atom abstraction reaction of O(-) with CH (sub 2) D (sub 2) is observed.