What has Quantum Chemistry Got to Do with It?

TheQuantum chemistry time has come to see how the concept of irreducible representationsRepresentationirreducible ties in with quantum chemistry. After a brief introduction to the pre-quantum principles of symmetry, it will be shown that eigenfunctionsEigenfunctions of the HamiltonianHamiltonian are also eigenfunctionsEigenfunctions of the symmetry operators that commute with the HamiltonianHamiltonian. The concept of a degeneracyDegeneracy is further analyzed, and it is shown how the degenerate components can be characterized by canonical symmetry-relationships. The final section will then provide a detailed account of the symmetry operations that leave the HamiltonianHamiltonian invariant.