ABSTRACT
Group theoretical consideration has greatly simplified problems in molecular physics, especially in the field of quantum chemistry. Under the Born-Oppenheimer approximation, the molecular Schrodinger equation is divided into the electronic Schrodinger equation and the nuclear Schrodinger equation. The symmetry property of molecular orbitals has been utilized also for discussions of the reactivity of molecules, and numerous theoretical schemes have been proposed. Symmetry coordinates are classified according to the irreducible representation, and molecular deformation keeping the symmetry can be described in terms of only total symmetry coordinates. Bader applied the second-order Jahn-Tellermechanism to study of the manner in which the electron density in a molecule is changed through a molecular vibration, and proposed a method to predict the symmetry of the reaction coordinate for both unimolecular and bimolecular reactions from the inspection of the electronic wavefunctions.
