State-Resolved and Bond-Selected Bimolecular Chemistry

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Professor Fleming Crim is supported by a grant from the Experimental Physical Chemistry Program to observe bimolecular reactions of highly vibrationally excited polyatomic molecules and to exploit the special nature of these states to directly control the course of chemical reactions. The object is to develop and test out schemes to control bond breaking in larger molecules and to make fully quantum-state-resolved measurements which can be compared with theoretical dynamical calculations. The essence of the technique is to excite an isolated vibration in a polyatomic molecule and to turn that vibration into a reaction coordinate by a collision with a reactive atom such as H or O. Reactions to be studied involve HCN, acetylene, ammonia, methane, propane, and methanol, using techniques such as stimulated emission pumping and laser-induced-fluorescence at vacuum ultraviolet wavelengths. %%% In this research the course of a chemical reaction between a polyatomic molecule and an atom is directly controlled by making use of vibrational excitation, based on the fact that the geometry change that occurs in going from reactants to products requires the stretching and breaking of bonds. Reactions involving collisions of energized molecules are central in atmospheric chemistry, combustion, and plasmas.