Surprising behaviors in the temperature dependent kinetics of diatomic interhalogens with anions and cations
Abstract
Rate constants and product branching fractions of reactions between diatomic interhalogens (ICl, ClF) and a series of anions (Br−, I−) and cations (Ar+, N2+) are measured using a selected ion flow tube apparatus and reported over the temperature range 200–500 K. The efficiency of both anion reactions with ICl is 2%-3% at 300 K to yield Cl−, increasing with temperature in a manner consistent with the small endothermicities of the reactions. The anion reactions with ClF are 10%–20% efficient at 300 K to yield Cl− and also show a positive temperature dependence despite being highly exothermic. The stationary points along the anion + ClF reaction coordinates were calculated using density functional theory, showing no endothermic barriers inhibiting reaction. The observed temperature dependence can be rationalized by a decreasing dipole attraction with increasing rotational energy, but confirmation requires trajectory calculations of the systems. All four cation reactions are fairly efficient at 300 K with small positive temperature dependences, despite large exothermicities to charge transfer. Three of the four reactions proceed exclusively by dissociative charge transfer to yield Cl+. The N2+ + ClF reaction proceeds by both non-dissociative and dissociative charge transfer, with the non-dissociative channel surprisingly increasing with increasing temperature. The origins of these behaviors are not clear and are discussed within the framework of charge-transfer reactions.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 07, 2017
- Source ID
- 10.1063/1.4984303
Entities
People
- Albert A Viggiano
- Hua Guo
- Justin P. Wiens
- Nicholas R. Keyes
- Nicholas S Shuman
- Oscar Martinez Jr.
- Shaun G Ard
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory
- University of New Mexico