Chemical Cartography: Finding the Keys to the Kinetic Labyrinth

Science  24 Nov 1989:
Vol. 246, Issue 4933, pp. 1009-1015
DOI: 10.1126/science.246.4933.1009


Very high resolution lasers allow spectroscopic pictures to be taken following a collision between two molecular reactants. The features of these "pictures" are the electronic, vibrational, rotational, and translational motions of the atomic particles, which relate the quantum states of the reactants to the quantum states of the products. Such state-to-state kinetic information can be used to test the shape and nature of the interaction potential that controls the collision process. The potential itself is akin to a map of the terrain through mountains and valleys where elevation is a measure of energy instead of height. Accurate mapping of this potential surface leads to an understanding of the forces which control rates and mechanisms of chemical reactions. The application of four different advanced laser techniques to the study of collisions between "hot" hydrogen(H) atoms and carbon dioxide(CO2) molecules has provided a wealth of information about both reactive and nonreactive collisions for this system. The availability of data for rotationally, vibrationally, and translationally inelastic excitation of CO2 by H atoms, when compared with data for reactive events producing OH + CO, provides insights into the dynamics of collisions between H and CO2, and illustrates the future promise of these powerful techniques for elucidating features of potential energy surfaces.

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