A Physicist’s Description of Chemical Oscillations

Abstract

Many examples of oscillations are known in physics: Rotations of planets, oscillations of a harmonic oscillator, rotation of an electron in a magnetic field, or the variety of eigenmodes in many-particle systems: sound waves, spin waves, etc. To study these oscillations theoretically, one usually starts from the energy of the system, derives the equations of motion which contain the reactive forces, and solves them for the eigenmodes, which result as undamped oscillations. Damping is introduced in a second step by adding appropriate dissipative forces in the equations of motion. Thus, there is a clear-cut distinction between reactive forces which follow from the energy and give rise to oscillations, and dissipative forces which follow from the entropy and lead to damping. In describing chemical oscillations, a different approach is usually applied. Energy is not considered, the equations of motion (the chemical kinetic equations) are immediately written down without any distinction between reactive and dissipative terms. Therefore, the driving force for chemical oscillations is not obvious.