Learning the Molecular Dance

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The world around us is made of atoms and molecules. They're the stuff of which we're made; we eat them, we breathe them. We live in a sea of them.

Chemical reactions are the dances that atoms and molecules engage in, dances that are continually recombining and rearranging these molecular partners in countless different ways. A good part of our modern understanding of chemical reactions stems from the work of UW chemistry professor B. Seymour Rabinovitch.

Rabinovitch joined the faculty in 1948. His work over the years was instrumental in unraveling the primary processes which take place when molecules collide and rearrange. His basic contributions to the field of molecular dynamics appear now as standard material in textbooks of physical chemistry.

Think of a molecule as a group of balls--atoms--joined together by springs--the chemical bonds between the atoms. The molecule can bend, twist, and vibrate in many ways much like the ball-and-spring model can.

Each molecule possesses certain special patterns of motion that are the preferred, or "normal," modes of vibration, as a guitar string has its harmonic frequencies. Molecules in reality are in constant motion, moving rapidly about, colliding with each other, and all the while vibrating and bending.

Rabinovitch and colleagues prepared chemical species with precisely known, fixed amounts of energy in order to see, for example, how long it takes for vibrational energy, delivered to only one pattern of movement, to spread to all the other vibrational modes. These fundamental vibrations play an important role in all chemical reactions.

Rabinovitch's group conducted fundamental studies of collisonal deactivation energy, the energy change in a molecule from a single collision in the gaseous state. More recently, these methods have been used to study gas-surface encounters.

Rabinovitch's work has permitted critical tests to be made of basic theories of chemical kinetics, work that has stimulated further applications to make molecules dance--and react--in exotic new ways. His work has been fundamental to many other investigations using powerful molecular beam and laser spectroscopy methods to characterize the dynamic processes involved in chemical reactions.

Today, chemical reactions can be observed on time scales as short as 10minus15 seconds (one quadrillionth of a second), allowing chemists to begin to describe chemical reactions in exquisite detail.

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