Low temperature (1-250 K) chemistry and collision dynamics of radicals and ions

University Of Arizona, Tucson AZ

Investigators

Abstract

Mark Smith of the University of Arizona is supported by a grant from the Experimental Physical Chemistry Program to study the mechanisms and dynamics of gas phase reactions from 300K down to temperatures of 1 Kelvin. These measurements will be performed on state selected reactants in free jet and supersonic Laval nozzle expansion cooled flow reactors with laser induced fluorescence, resonance enhanced multi-photon ionization and mass spectrometric probing. Absolute reaction rate constants and product branching ratios will be determined for a series of ion-molecule (quenching and reaction of hydrogen halide ions), radical-molecule (hydrogen and carbon atom, cyanide and hydroxyl reactions with various hydrocarbons and other small molecules) and molecule-molecule (nitric oxide self quenching) reactions, many with astrochemical applications. Comparisons will be made with theoretical calculations and higher temperature experimental measurements. Electronic predissociation spectroscopy of small ions will be explored as a means of following the reactions in a quantum specific fashion. These studies will lead to a greater understanding of how ions and molecules react at very low temperatures and provide fundamental information on the mechanisms of the reactions. They will show how fast the reactions are, what products are generated and how these depend on the available energy. These reactions are important in planetary atmospheres, including that of the Earth, and in interstellar space.