ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
A selected ion flow tube study has been carried out at 300 K of the reactions of some atomic and molecular positive and negative halogen ions with Cl2 and Br2 from which the rate coefficients k and ion product distributions have been determined. For the energetic F+ ion reactions, dissociative charge transfer is the dominant process, while for the Cl+ ions, only nondissociative charge transfer occurs. For the less energetic Br+ and I+ reactions, dihalogen molecular ions are important products. All these positive ion reactions proceed quite efficiently, i.e., the k are appreciable fractions of kc, their respective collisional rate coefficients, except for the reactions of Cl2 with the lower energy ions of the spin–orbit triplet of I+, i.e., I+(3P1,0), for which k∼0.07kc, this being due to the endothermicities of the reactions. The molecular ion Cl2+ undergoes rapid nondissociative charge transfer with Br2, a process which is, of course, endothermic for the reaction of Br2+ with Cl2 and so no reaction is observed. The less-energetic atomic negative ion reactions proceed—via atom exchange—in which the atomic negative ion of the reactant molecular species and a dihalogen molecule are produced. For those reactions that are exothermic, the k are, within error, equal to (2/3)kc, implying that they proceed via complexes which separate statistically back to reactants (1/3) and forward to products (2/3). Both the Br−+Cl2 and Cl−+Br2 reactions are somewhat less efficient (i.e., k〈2/3kc), a result of the slight endothermicities of the reactions. Of the molecular negative ion reactions, electron transfer is the major process in the Cl2− reaction with Br2, whereas the reaction of Br2− with Cl2 proceeds relatively slowly producing the triatomic ion BrCl2−.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.464473
